Tag: Epidemiology

The world is watching South Korea as the latest outbreak of Middle East respiratory syndrome (MERS) unfolds. But how exactly the virus jumps to humans in the first place is still unknown, and clues to that puzzle lie thousands of kilometres away.

The cluster of hospital-associated cases in South Korea — the largest MERS outbreak outside the Middle East — has so far killed 7 people and infected 95, according to the World Health Organization (WHO). Hundreds of schools have been shut. Although the causal coronavirus, MERS-CoV, is considered a potential pandemic threat, specialists told Nature that they expect authorities to quickly bring this outbreak under control.

A much bigger challenge than emergency response, they say, is how to stop MERS being transmitted from animals to people in the Middle East, where it is endemic in camels. “The focus on South Korea would be better directed towards Saudi Arabia,” says David Heymann, a researcher at the London School of Hygiene and Tropical Medicine and chair of Public Health England, to stop the cases that continue to spark new outbreaks at the source.

Since it was first detected in Saudi Arabia in 2012, MERS-CoV has infected around 1,200 people worldwide, roughly 450 of whom have died, according to the WHO. The virus is thought to originate in bats and to jump to humans through an intermediate animal, such as camels. It does not easily spread between people, partly because it infects deep areas of the lungs, and is not coughed out. Most of the human infections, however, were the result of human-to-human spread, which can occur in hospitals when certain medical procedures combine with poor infection control to disseminate the virus. The latest clusters began when a South Korean man returned to Seoul from the Middle East, and visited four health-care facilities before he was diagnosed.

There is always a chance that as the virus spreads, it could acquire mutations that allow it to spread more easily between humans. But on 6 June, the South Korean health ministry announced that it had sequenced the virus in the current outbreak and that it was almost identical to past sequences from the Middle East. On the same day, the Chinese Center for Disease Control and Prevention posted a separate sequence to the publicly available GenBank database, from a man infected in the South Korean outbreak who then travelled to China, where he felt ill. Christian Drosten, director of the Institute of Virology at the University of Bonn Medical Centre in Germany has analysed this sequence and says that it is shows only minor mutations compared with Middle Eastern strains, none in areas of the genome thought to influence infectiousness.

A stream of new cases in South Korea might create the impression that the disease is out of control. But all cases reported so far have clear transmission routes from the initial infection, says Ian Lipkin, an outbreak specialist at Columbia University in New York. The country is now intensively tracing and isolating the contacts of those infected, and implementing strict infection controls in hospitals. Were cases springing up outside of hospitals that would be cause for worry, but that is not happening, says Lipkin.

In the Middle East, however, the virus continues to jump from camels to humans leading to hospital outbreaks. Heymann, who in 2003 led the global effort to contain severe acute respiratory syndrome, or SARS, says that authorities in the Middle East should do more to investigate how people catch the virus from camels.

Such studies would involve investigating the recent activities of infected people, finding out, for instance, whether they had had contact with animal carcasses or bodily fluids, had consumed fluids such as camel milk or urine, or had been near bat colonies. “It’s frustrating that all cases from animal infections have not been properly investigated,” says Peter Ben Embarek, leader of the WHO’s MERS team at the agency’s headquarters in Geneva, Switzerland. One obstacle is cultural, in that Saudis tend to be averse to discussing what they consider private matters, he says. The outbreak in South Korea will probably put pressure on Middle Eastern countries to accelerate research and control of MERS, says Drosten.

Another outstanding mystery is why human cases have not been detected in African countries with large camel populations: Somalia has 7 million camels, and Kenya 3 million, dwarfing Saudi Arabia’s population of 260,000. “MERS is circulating in camels in many parts of Africa,” says Ben Embarek, “so camel-wise, it’s the same picture as in the Middle East.” One possibility is that human cases are going undetected because of poor surveillance. Another possibility is that cases in Africa are less likely or less serious, because MERS tends to cause serious illness only in people who have diseases that result from modern lifestyles, such as diabetes, which are more common in Saudi Arabia.

Nature 522, 139–140 (11 June 2015) doi:10.1038/522139a

http://www.nature.com/news/index.html  Nature

http://www.nature.com/news/south-korean-mers-outbreak-spotlights-lack-of-research-1.17722 Original web page at Nature

On Dec. 26, 2013, a two-year-old boy living in the Guinean village of Meliandou, Guéckédou Prefecture was stricken with a rare disease, caused by the filament-shaped Ebola virus. The child is believed to be the first case in what soon became a flood-tide of contagion, ravaging the West African countries of Guinea, Sierra Leone and Liberia, infecting, according to the World Health Organization, over 21,000 cases as of Jan. 21, with nearly 9000 confirmed deaths–the actual toll likely much higher. Now, researchers from Arizona State University and Georgia State University are trying to better understand the epidemiology and control of Ebola Virus Disease in order to alleviate suffering and prevent future disease outbreaks from reaching the catastrophic proportions of the current crisis. In reports appearing in the February 2015 issue of the British medical journal The Lancet Infectious Disease, ASU researchers report on new efforts to model the impact of timely diagnostic testing on the spread of Ebola across populations. A better understanding of viral dissemination and techniques for disease management are vital if a similar calamity is to be avoided in the future.

Researchers from the Biodesign Institute, and the Simon A. Levin Mathematical, Computational and Modeling Sciences Center present a new study: Modelling the effect of early detection of Ebola. The study examines the levels of detection and patient isolation required to shut down transmission of Ebola. In related research, Gerardo Chowell, a newly appointed faculty member in the School of Public Health at Georgia State University and adjunct faculty member in the ASU’s Simon A. Levin Mathematical, Computational and Modeling Sciences Center, together with Cécile Viboud from the from the National Institutes of Health discuss recent large-scale modeling efforts to explain the spatial-temporal patterns of spread of the epidemic in Liberia. Chowell is also co-author of Ebola control: rapid diagnostic testing, which appears in the Lancet’s correspondence section.

The Ebola virus has become notorious, not only for its highly contagious and lethal nature, but for the nightmarish assortment of symptoms collectively known as hemorrhagic fever. These may include vomiting of blood, bleeding from the eyes, ears, nose, mouth, rectum, internal bleeding, excruciating pain and the liquidization of internal organs. The three West African nations centrally affected by the epidemic were acutely unprepared for the crisis. Treatment centers were rapidly swamped with severely ill patients. Resources for proper care, isolation of infected patients and even basic means of sterilization were soon depleted. Health care workers were especially vulnerable to infection. A number of exacerbating factors contributed to the outbreak and rapid spread of Ebola in the region. Timber and mining activities have impacted densely forested regions and brought fruit bats–believed to be a natural reservoir for the virus–in closer contact with humans. Infected animals consumed as bush meat may also have planted early seeds of the disease in the vulnerable population. Long periods of civil unrest have left the area deeply impoverished and the health infrastructure fractured. Meliandou, the town identified as ground zero, is situated in a forested area at the convergence point of Guinea, Liberia and Sierra Leone. Populations move fluidly across these porous borders, as impoverished residents are often on the move in search of work. These conditions created a perfect storm for the aggressive virus.

An additional factor fueling the explosive spread of Ebola in West Africa was the delayed and inadequate response to the crisis on the part of developed countries and global health organizations. As the authors of the Lancet modeling study emphasize, breaking the chain of Ebola transmission presents intimidating challenges. After the development of symptoms, the virus is highly contagious and each new contact presents an opportunity for further spread of the disease. Tracking all contacts of infected individuals can be a daunting challenge, even in first world settings, with low case numbers. In the absence of a vaccine or reliable therapeutic for Ebola, diagnosis of the disease at a pre-symptomatic stage and rapid isolation of infected individuals are the surest means for arresting further disease transmission.

According to Biodesign’s Karen Anderson, PhD., “Early detection of Ebola infection provides the opportunity and time to safely isolate and treat individuals before they become contagious. Our findings show two key things: first, that the predicted impact of early diagnostic tests depends on existing public health measures. Second, there appears to be a tipping point, where early diagnosis of high-risk individuals, combined with adequate isolation, can markedly decrease the predicted number of infected individuals.” Stopping an epidemic in its tracks requires a reduction in a critical value known as the reproductive ratio or R0– a measure of new infections generated by a single case over the course of the infectious period. The higher the number for R0, the more difficult an epidemic is to contain. A technique known as polymerase chain reaction (PCR) can be used for pre-symptomatic identification of the Ebola virus. The current study models the expected outcomes on viral transmission of Ebola using PCR-based pre-symptomatic diagnosis and isolation of infected patients within 3 days of the onset of symptoms. “Our results underscore the dramatic impact that diagnostic capacity can bring about during an Ebola epidemic to quickly identify Ebola cases before these start new chains of transmission in the community or health care settings,” according to Diego Chowell, lead author of the study. Carlos Castillo-Chavez, director of the Simon A. Levin Mathematical, Computational and Modeling Sciences Center, emphasises the power of mathematical modeling for understanding and limiting the scale of epidemics: “Finding that small differences in isolation effectiveness may have a large impact on epidemic size highlights the importance of evaluating novel diagnostic technologies at the population level using mathematical models,” he says. “An intervention may not work or be effective unless it is effectively used beyond a tipping point.” The authors urge the implementation of the strategy of pre-symptomatic diagnosis and rapid isolation, targeting high-risk individuals, including care givers and health care workers.

In his comment to the Lancet, Geraldo Chowell examines another mathematical model, put forward by Merler and his colleagues. This study models the course of the Ebola epidemic in Liberia, based on population structure and geography, including location of households, hospitals, and Ebola treatment units. Chowell notes that the establishment of new treatment centers, isolation of new patients and distribution of household protection kits all likely played a role in curtailing the spread of Ebola in Liberia, relative to neighboring states of Guinea and Sierra Leone. “Carefully calibrated mathematical models have potential to guide public health authorities to effectively respond to disease epidemics,” Chowell says. “In the context of the Ebola epidemic in West Africa, several key factors, including delays in responding to the epidemic, behavior changes and increased public health infrastructure in the region in order to trace contacts of infected individuals and break chains of transmission through effective isolation have played a major role in shaping the trajectory of this epidemic.” The desperate need for early diagnosis of Ebola was further emphasized in Chowell’s correspondence, which points out that most West African Ebola patients remained undiagnosed in their communities and the average time from symptom onset to diagnosis was about 5 days–a prescription for rapid, far-flung transmission of the disease. While underscoring the diagnostic power of PCR, Chowell notes that such tests presently require transportation to a laboratory or transit center, causing critical delays in diagnosis and treatment and heightening transmission risks. His recommendation is to supplement these efforts with the distribution of point-of-care rapid tests that could be used in households for early protection. Chowell and his colleagues conducted a simulation based on reducing the time between symptom onset and diagnosis, using rapid testing. The results were dramatic. If 60 percent of Ebola patients can be rapidly diagnosed and isolated (within 1 day of symptom onset), the proportion of the population eventually infected (known as the attack rate) drops from 80 percent to nearly zero.

While authors of the current Lancet papers model Ebola transmission and propose strategies to address future epidemics, ASU has also been on the forefront of efforts toward Ebola therapeutics and eventual vaccines. Charles Arntzen, Ph.D., offered a prescient warning back in 2011 that the next outbreak of Ebola could be far more devastating than those in the past, if sufficient resources were not immediately brought to bear. Regrettably, Arntzen’s prediction became a reality with the recent epidemic, far surpassing in death toll and geographic extent all previous Ebola outbreaks combined. Arntzen’s earlier study in the Proceedings of the National Academy of Science described an experimental cocktail of monoclonal antibodies produced from tobacco plants, which showed considerable promise in animal studies. The recent West African epidemic provided an unprecedented opportunity to test the effectiveness of the drug formula, developed with Arntzen’s longtime collaborators at San Diego based MAPP Pharmaceuticals. Two health care workers returning to the U.S. after having been stricken with Ebola in Africa were treated with the drug, known as ZMapp. Both survived, offering the tantalizing potential for a safe, highly effective vaccine against the disease. Arntzen’s efforts also highlighted the potential of similar plant-made pharmaceuticals. A number of these are currently being investigated at the Biodesign Institute by Qiang “Shawn” Chen, Ph.D., a researcher in the Center for Infectious Diseases and Vaccinology. Chen hopes to apply similar techniques to produce therapeutics against other diseases, including West Nile Fever, a focus of current research.

According to the latest reports from the World Health Organization, the Ebola epidemic appears to be weakening its grip on the region. For the first time since June 2014, there have been fewer than 100 new weekly cases reported in the 3 countries most affected, signaling what health care workers hope is the final phase of Ebola’s devastating reign. Increased vigilance and new tools at both the epidemiological and therapeutic ends of the spectrum are vitally needed, if another epidemic–perhaps of even greater scale–is to be prevented.

http://www.sciencedaily.com/ Science Daily

http://www.sciencedaily.com/releases/2015/02/150206111704.htm Original web page at Science Daily

The Ebola outbreak in West Africa continues to rage, with the number of people infected roughly doubling every 3–4 weeks. More than 8,000 people are thought to have contracted the disease, and almost half of those have died, according to the World Health Organization. Although these estimates are already staggering, the situation on the ground means that not all cases and deaths are being reported, so the true extent is likely to be much greater. Outside of Africa, a health-care worker in Texas has become infected while treating a patient who was hospitalized in Dallas after travelling from Liberia and who has now died. And a nurse in Madrid has contracted the virus after caring for a missionary who had become infected while caring for patients in West Africa. Health-care workers remain one of the groups at highest risk of exposure: by 8 October, 416 had become infected and 233 had died.  The spread beyond the epicentre of Guinea, Liberia and Sierra Leone remains limited. Apart from the people in Dallas and Spain, only two other exported cases are known: one in Nigeria and one in Senegal. A man who travelled to Lagos from Liberia sparked a further 19 cases in Nigeria, but that outbreak was curtailed by the swift actions of the authorities in tracing and monitoring those who had contact with the infected man. Similar public-health measures stopped further cases in Senegal after an infected man travelled from Guinea to Dakar.  Within the epicentre, authorities have made some progress in slowing transmission — but the disease is resurgent in places where it had seemed under control, such as in Conakry, Guinea’s capital. Meanwhile, the estimated cost of fighting the disease is spiralling upward. UN secretary-general Ban Ki-moon warned on 9 October that “at least a 20-fold surge in assistance” was needed to confront the outbreak. But “things will get worse before they get better”, he warned. Just how much worse will depend on the international community — which has been widely criticized for its belated response, and its slow translation of pledges into concrete action.

http://www.nature.com/news/index.html  Nature

http://www.nature.com/news/ebola-by-the-numbers-the-size-spread-and-cost-of-an-outbreak-1.16144  Original web page at Nature

Deadly Ebola probably touched down in Lagos, Nigeria, the largest city in Africa, on 20 July. A man who was thought to be infected with the virus had arrived there on a flight from Liberia, where, along with Guinea and Sierra Leone, the largest recorded Ebola outbreak is currently raging. The Lagos case is the first to be internationally exported by air travel and today the UK foreign secretary announced that he would chair a government meeting on Ebola. As long as the virus continues to infect people in Liberia, Guinea and Sierra Leone, there is a small risk of more long-distance exports of the disease. But, as Nature’s Declan Butler explains, Ebola does not pose a global threat. The World Health Organization still considers the Lagos case a “probable” infection because it has not yet confirmed that the 40-year-old Liberian man had Ebola. He was quarantined upon arrival at the airport and taken to hospital, where he died on 25 July. Assuming he had Ebola, if proper control measures were taken at the airport and at the hospital, the risk that health-care workers or others will become infected as a result of contact with him is low. The European Centre for Disease Prevention and Control classifies people sharing public transport with someone infected as having a “very low” risk of catching the virus. Healthcare workers and doctors, several of whom have now been infected and died as a result of caring for people in the current outbreak, are at much higher risk and the WHO advises that they take strict precautions, which greatly lowers the risk. The ECDC also says the probability of an infected person getting on a flight in the first place is low, given the small overall number of Ebola cases. Moreover, functional health systems should be able to prevent onward spread from any exported cases. Overall, the World Health Organisation estimates that there is a high risk of spread to countries bordering those with existing outbreaks, a moderate risk to countries further afield in the sub-region, but that there is little chance of spread overseas. There is no reason to assume that an exported case — be it to Lagos, a city of 17 million people, or any other place — will spark new outbreaks, because Ebola is not highly contagious.

Though the strain of Ebola in the current outbreak appears to kill 56% of the people it infects, to become infected in the first place, a person’s mucous membranes, or an area of broken skin, must come into contact with the bodily fluids of an infected person, such as blood, urine, saliva, semen or stools, or materials contaminated with these fluids such as soiled clothing or bed linen. By contrast, respiratory pathogens such as those that cause the common cold or flu are coughed and sneezed into the air and can be contracted just by breathing or touching contaminated surfaces, such as door knobs. A pandemic flu virus can spread around the world in days or weeks and may be unstoppable whereas Ebola only causes sporadic localised outbreaks that can usually be stamped out. In principle, it should be straightforward to bring an Ebola outbreak under control via public health measures alone, namely, identifying all people who have been infected and isolating them, monitoring all those that they have been in contact with for 21 days (the maximum incubation period), as well as promoting basic infection control measures. What’s more, since people infected with Ebola do not infect others until they have symptoms, it is easier to trace their contacts than it is for some other diseases. Ebola is out of control in these countries because the sheer size of the outbreak is stretching response teams, and also because of local sociocultural factors. Local health authorities and international organisations such as WHO and Médecins Sans Frontières (also known as Doctors Without Borders) are struggling to control the spread in these areas because of a lack of trust and cooperation among the affected populations. Doctors and health workers have sometimes been blocked from accessing affected places because of opposition from villagers who fear the medics will bring the disease. According to the WHO, not all people who are infected are getting or seeking care, and so are passing the virus on to family and other close contacts. Another major driver of new infections is that families are often continuing to perform traditional burial rites that involve mourners having direct contact with the bodies of the dead – and unfortunately all too often Ebola. It is larger than any other outbreak in recorded history. The WHO reports that as of 23 July, there were 814 lab-confirmed infections, including 456 deaths. If ‘probable’ and ‘suspected’ cases are included, these numbers rise to 1,201 infections, including 672 deaths — but some of these may have been caused by other diseases. Only 7 other of the few dozen past outbreaks have involved more than 100 cases, and before now, the largest outbreak was in Uganda between 2000 and 2001, in which 425 people were infected and 224 died.

Since Ebola first appeared in 1976, only 19 outbreaks have had more than 10 victims, and around 2,000 people in total have died from the disease. By comparison, malaria kills some 3,200 people a day, and diarrhoeal diseases some 4,000. Snakes and other venomous animals cause some 55,000 deaths a year — 27 times more than the entire number of people killed by Ebola in 38 years. There are no licensed drugs or vaccines for Ebola, although candidates are in development. New treatments would help reduce the high mortality rate of the disease – which has ranged in past outbreaks from 25% to 89%, with an average of around 62%. Jeremy Farrar, head of the UK Wellcome Trust in London, has argued for the use of experimental, unapproved drugs in the current outbreak. But other scientists have said that with distrust of health workers already hampering efforts to bring the outbreak under control, such measures could be counterproductive by creating suspicion and so further undermining trust. Outreach, in particular involving local community leaders, will be vital to persuade people to trust health workers and to follow public-health advice. Authorities need to win over public trust, persuade people to bury their dead safely, and continue to step up local and regional efforts to trace and isolate people who are infected and their contacts.

Nature doi:10.1038/nature.2014.15640

http://www.nature.com/news/index.html  Nature

http://www.nature.com/news/largest-ever-ebola-outbreak-is-not-a-global-threat-1.15640 Original web page at Nature

Workers at the US Centers for Disease Control and Prevention in Atlanta, Georgia, accidentally shipped highly dangerous H5N1 influenza virus to another government laboratory in March, the agency revealed today. The news comes weeks after the CDC announced that dozens of its employees were potentially exposed to anthrax because its staff did not follow established laboratory safety guidelines. In response to the incidents, the CDC today imposed a moratorium on shipments from its high-biosecurity facilities and shut down the laboratories responsible for the anthrax and H5N1 incidents, pending an investigation. “I’m disappointed by what happened and frankly I’m angry,” agency director Thomas Frieden said at a press conference. After news of the anthrax exposure broke on 19 June, the CDC began investigating why its lab workers did not follow proper procedure to inactivate Bacillus anthracis spores before shipping them to another lab on the agency’s Atlanta campus. The receiving lab was not equipped to handle the pathogen, and once the mistake was discovered, more than 70 people were pre-emptively treated for anthrax infection. The CDC now says that the lab never needed to work with B. anthracis in the first place; another bacterium would have sufficed to test the diagnostic equipment that the lab was evaluating. The good news, Frieden says, is that the CDC now does not believe that anyone was actually exposed to anthrax spores. But the agency’s ongoing investigation has revealed more bad news: on 12–13 March, the CDC’s influenza lab contaminated a harmless flu strain with the highly dangerous H5N1 variety, and sent it to a laboratory operated by the US Department of Agriculture (USDA) in Athens, Georgia. The mistake was discovered on 23 May, but Frieden says that he was not notified until 9 July. “Why it took six weeks for that to be made apparent, I can think of no valid explanation,” he says. The USDA lab was equipped to handle highly infectious agents, and the agency is confident that there were no exposures. According to a CDC report released on 11 July, at least five such incidents have happened in the past decade, in which CDC shipments of potentially viable pathogens — including those that cause botulism, anthrax and brucellosis — were improperly inactivated or wrongly believed to be harmless. “These are wakeup calls,” Frieden says. “These are events that tell us we have a problem, and we are going to fix it.”

The CDC says that it will work with an external scientific advisory panel to examine safety procedures at all of its high-level biosafety labs before resuming any shipments to internal or external labs. The influenza and anthrax labs are shut indefinitely, pending completion of the investigations, but Frieden expects that the influenza lab will reopen in time for tracking the flu season this autumn. The agency is also instituting new safety measures, including a review of its training procedures and appointing CDC health-care safety expert Michael Bell to act as a single point of accountability for future biosafety incidents. Frieden also says that employees who are found to have knowingly violated lab safety procedures will face disciplinary action. News of the CDC troubles “points out that accidents can happen anywhere”, even at the agency charged with overseeing US biosecurity, says Michael Osterholm, a public-health expert at the University of Minnesota in Minneapolis. He sees the H5N1 incident as a reason to question ‘gain-of-function’ research that involves engineering disease-causing viruses to make them more deadly, in order to understand what might happen if such viruses evolved naturally to become more pathogenic. If there is any silver lining to the CDC incidents, Osterholm says, “it’s that we will have a heightened level of lab safety and a discussion that I think has been long overdue.” The CDC’s actions come on the heels of another biosafety scare earlier this week, when unauthorized vials of smallpox were found in a cold storage room on the National Institutes of Health campus in Bethesda, Maryland. The CDC said today that its tests show that virus samples from at least two of the twelve vials were able to successfully infect and replicate in cultured human cells. Frieden says that the vials will now be destroyed with the World Health Organization in attendance as a witness. “That’s what should have been done a couple decades ago,” he says.

Nature doi:10.1038/nature.2014.15544

http://www.nature.com/news/index.html  Nature

http://www.nature.com/news/us-disease-agency-suspends-pathogen-shipments-1.15544  Original web page at Nature

Breaking research appearing online today in Clinical Chemistry, the journal of AACC, demonstrates that a recently developed diagnostic test can detect the new strain of influenza (H7N9) currently causing an outbreak in China. Since the end of March, 31 people have died from H7N9 infection, and the number of confirmed cases has climbed to 129. Evidence suggests that most H7N9 infections have arisen from poultry-to-human transmission, and that passage of the virus between humans is limited. However, researchers have also found mutations in the virus that are known to help avian viruses adapt to mammalian hosts. If these mutations lead to sustained human-to-human transmission, a serious pandemic could occur. In this study, Wong et al. designed a diagnostic test with high specificity for the H7N9 virus that does not cross react with distantly related viruses, including all previously known avian and mammalian H7 viruses. They also show that this one-step quantitative real-time PCR assay enables specimen processing in about 3 hours. According to the authors, this new test should also detect viruses closely related to the H7N9 virus.

If confirmed, this capability could prove vital; it’s likely that the H7N9 virus is evolving rapidly, and there could be multiple introductions of avian H7N9 viruses from animals to humans. The test also demonstrates a detection limit of ~0.04 median tissue culture infective dose (TCID50) per reaction. This means that it should be sensitive enough to identify patients with active virus replications. “These results suggest that the established assay should be suitable for screening H7N9 viruses in human samples,” said lead investigator Leo Poon, PhD, of the University of Hong Kong, though additional evaluation using clinical specimens from H7N9 patients is needed. If validated, this diagnostic test could help health officials avert a potential pandemic by allowing them to monitor the spread of the virus. The test could also identify H7N9 patients in the early stages of infection, improving their chances of responding to clinical treatments.

Science Daily
May 28, 2013

Original web page at Science Daily

Pandemic flu continues to threaten public health, especially in the wake of the recent emergence of an H7N9 low pathogenic avian influenza strain in humans. A recent study published in PLoS ONE, a peer-reviewed scientific journal, provides new information for public health officials on mitigating the spread of infection from emerging flu viruses. Dr. Henry Wan, associate professor at the Mississippi State University College of Veterinary Medicine led a study with researchers from Georgia Institute of Technology, Marshall University, and Universidad Miguel Hernández in Spain called “A perspective on multiple waves of influenza pandemics” that brings new insight into the H1N1 pandemic of 2009, and may help officials prepare for future pandemics. During the 2009 H1N1 pandemic, along with the last three flu pandemics of 1918, 1957, and 1968, the United States experienced multiple peaks, or waves, of infection. Normal seasonal flu outbreaks have only one peak of infection–the number of cases starts very low, increases to a maximum, then decreases to a very low level, and remains at a low level until the next flu season. In this study, the team developed models to explain possible causes of the multiple peaks in pandemic flu, which are largely unknown.

“With the H1N1 pandemic in 2009, we experienced multiple waves of infection,” Dr. Wan said. “The first wave began in March 2009 and peaked in late June and early July. Then there were fewer cases in August and then a second, larger wave hit in late October and early November. But China only experienced a single wave of infection. So we created infection models and analyzed the outcomes.” The models showed that border control had some small effects on outbreaks. “In 2009, China instituted strict border controls at the onset of the outbreak,” said first author Dr. Anna Mummert, assistant professor of mathematics at Marshall University. “We developed models explaining the occurrence of the multiple peaks and tested border control strategies to determine if a strict border control in the United States could reduce the total number of infections.” Four of the models indicated that if that stricter border control is related to fewer waves of infection. “What was really remarkable was that all of the models showed that strong border control would not have decreased the total number of infections,” said Dr. Howie Weiss, professor in Georgia Tech’s School of Mathematics or College of Sciences. The effects of vaccinations were studied in the models, and the authors concluded that the actual H1N1 vaccination distribution schedule played only a small role in curtailing the outbreak. While it has been thought that the timing of school vaccinations played a large role in producing the second wave of infections, the models did not show a strong link, but indicated that an earlier vaccination schedule could have helped. The research team plans further collaboration in understanding influenza viruses and their spread. “We are fortunate to have each other’s expertise in mathematical modeling and infectious diseases,” Wan said. “Our goal is to provide timely information to health organizations and others who work on infectious disease prevention.”

Science Daily
May 14, 2013

Original web page at Science Daily

To determine whether persons living in areas of high animal density are at increased risk for carrying livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA), we used an existing dataset of persons in the Netherlands with LA-MRSA carriage and controls who carried other types of MRSA. Results of running univariate and multivariate logistic regression models indicated that living in livestock-dense areas increases the odds of nasal carriage of LA-MRSA. We found that doubling pig, cattle, and veal calf densities per municipality increased the odds of LA-MRSA carriage over carriage of other types of MRSA by 24.7% (95% CI 0.9%–54.2%), 76.9% (95% CI 11.3%–81.3%), and 24.1% (95% CI 5.5%–45.9%), respectively, after adjusting for direct animal contact, living in a rural area, and the probable source of MRSA carriage. Controlling the spread of LA-MRSA thus requires giving attention to community members in animal-dense regions who are unaffiliated with livestock farming.

Emerging Infectious Diseases
November 13, 2012

Original article at Emerging Infectious Diseases

Scientists at Case Western Reserve University and the Cleveland Clinic Lerner Research Institute have discovered that the parasite that causes the most common form of malaria share the same genetic variations — even when the organisms are separated across continents. The discovery raises concerns that mutations to resist existing medications could spread worldwide, making global eradication efforts even more difficult. The researchers, including Cleveland-based David Serre and Peter Zimmerman, Didier Menard (Institut Pasteur-Cambodia) and Arsene Ratsimbasoa (Madagascar National Malaria Control Program) are the first to sequence the genome of the parasite Plasmodium vivax, taken from patients at coverage needed to verify genome-wide DNA sequence variation. The genome contains all of the organism’s inheritable information. The ability to sequence is crucial to understanding the hard-to-study parasite, which annually causes up to 250 million cases of malaria and places an economic burden, mostly on the poor, in excess of $1.4 billion by some estimates. The researchers report their findings in the Sept. 6 issue of the online journal PLoS Neglected Tropical Diseases.

The scientists at first were surprised to find little genetic variation specific to different locations among the samples, which came from humans in Madagascar and Cambodia and South America. How can parasites, transmitted by mosquitoes, share genome-wide variations on three continents? “The parasite’s life cycle enables P. vivax to be a microbial globe-trotter,” said Peter Zimmerman, professor of international health, genetics and biology in the Center for Global Health and Diseases at Case Western Reserve University School of Medicine. In parts of the world where Plasmodium vivax malaria is endemic, the primary infection gets into the red blood cells and makes people sick, he explained. When they feel better, people resume their normal activities and travel. But a portion of the infectious form can remain in their liver, where it may lay dormant for months or a year, then re-emerges into the blood when that person is in a different place. “In that new place, local mosquitoes bite, become infected, and start spreading the P. vivax parasite and its genome in locations that can be a long distance away from where the original human infection occurred,” Zimmerman, a senior author of the new study, said. This ability for worldwide travel raises concerns among the researchers. There is no vaccine and there is only one drug that kills the parasite in the liver.

“If drug resistance arises, with modern travel, how long would it be before the resistance is spread over the world?” Zimmerman said. “This data suggests it could quickly become a big problem.” Learning how Plasmodium vivax lives and causes malaria has been challenging because the parasite dies when removed from its host. With improvements in sequencing techniques and reductions in costs, David Serre, Assistant Professor, at the Genomic Medicine Institute, Cleveland Clinic Lerner Research Institute, and Zimmerman decided to try to see if the parasite’s genome could be sequenced and what it might tell. “Our work provides the first report on genome-wide variation of this malaria parasite and provides the malaria research community with more than 80,000 genetic markers that can now be used for trait mapping or population monitoring,” Serre said. “This is a critical step to understand the biology of this parasite that cannot be studied in the laboratory yet affects millions of people each year.” Serre and Ernest R. Chan, a postdoctoral research fellow at the Genomic Medicine Institute, sequenced the genomes of parasites in blood samples taken from two P. vivax malaria patients in Madagascar and three in Cambodia, after first removing the white blood cells. For comparison, they sequenced P. vivax from a monkey that had been infected with a human strain of the parasite found in South America. The results showed the six samples extensively shared alternative forms of the same gene, called alleles.

Sequencing parasite strains straight from humans is a big step forward, Serre said. Most researchers have been studying human strains of ,P. vivax propagated through monkeys. This method is not as reliable as using human samples, because it introduces variability, and is limited to only about a dozen strains that have been adapted to monkeys. Far more strains have been found in humans. The 80,000 genetic markers identified can now be used to search for links to drug-resistant malaria, a growing problem in Southeast Asia; and to study possible new treatments for P. vivax malaria. Zimmerman and Serre are seeking grants to expand their work, sequencing more samples from more locations. The researchers will use the data to perform genetic evolution studies to learn where the parasite originated, how it spreads, and how different strains are geographically distributed. The team will also study evolving P. vivax infection mechanisms. For example, in a classic example of natural selection, African persons do not develop P. vivax malaria, but the disease is prevalent in nearby Madagascar. Serre and Zimmerman believe specific mutations in Malagasy P. vivax strains make the parasite able to infect individuals previously thought to be resistant.

Science Daily
September 18, 2012

Original web page at Science Daily

Healthcare workers who wear gloves while treating patients are much less likely to clean their hands before and after patient contact, according to a study published in the December issue of Infection Control and Hospital Epidemiology, the journal of the Society for Healthcare Epidemiology of America. This failure of basic hand hygiene could be contributing to the spread of infection in healthcare settings, the researchers say. Glove use is appropriate for situations when contact with body fluids is anticipated or when patients are to be managed with contact precautions. However, use of gloves should not be considered a substitute for effective hand hygiene practices taking place before and after patient contact. Although gloves can reduce the number of germs transmitted to the hands, germs can sometimes still get through latex. Hands can also be contaminated by “back spray” when gloves are removed after contact with body fluids.

The researchers, led by Dr. Sheldon Stone of the Royal Free Hospital NHS Trust, observed more than 7,000 patient contacts in 56 intensive care and acute care of the elderly wards in 15 United Kingdom hospitals, making this one of the largest and most detailed studies on gloves and their impact on hand hygiene. Overall, the study found that hand hygiene compliance was “disappointingly low,” at just 47.7 percent. Compliance was even lower in instances where gloves were worn, dipping to just over 41 percent. “The chances of hands being cleaned before or after patient contact appear to be substantially lower if gloves were being worn,” said Dr. Stone, the principal investigator. “We call this the phenomenon of the ‘Dirty Hand in the Latex Glove.'” Though troubling, the results also reveal an opportunity to reduce healthcare associated infections by focusing further hand hygiene improvement efforts on better hand hygiene when using gloves. Doing so may prove the critical step in getting overall hand hygiene levels to the levels needed to prevent transmission of infection, the researchers say. Dr. Stone and his colleagues suggest further study on the behavioral reasons behind why healthcare workers are less likely to wash their hands when wearing gloves. Regardless, the researchers recommend that campaigns such as the World Health Organization’s Clean Care is Safer Care program should emphasize better hand hygiene associated with gloving practices.

EurekAlert! Medicine
November 15, 2011

Original web page at EurekAlert! Medicine