NEWS SCAN: CDC on H5N1 clade, avian-flu prevention in Egypt, cyclical H5N1, flu cross-protection, Southern Hemisphere H1N1 patterns, flu diagnostic kit

Sep 2, 2011

CDC says Vietnamese H5N1 clade is not new
The US Centers for Disease Control and Prevention (CDC) yesterday weighed in on recent media coverage regarding clade 2.3.2.1 H5N1 avian influenza viruses. On Aug 29 the United Nations Food and Agriculture Organization (FAO) issued a press release emphasizing that H5N1 vaccines currently used in Vietnam don't protect poultry against new H5N1 clades. The CDC said some media reports have mischaracterized the FAO report, implying that a new mutant strain is spreading and posing a greater risk to human health. The CDC said the 2.3.2.1 clade that was the subject of the FAO statement is not new and was first identified in Vietnamese poultry in 2009. Though the clade is spreading actively in birds, which could increase human exposure to the virus, circulation does not increase its ability to infect and transmit between people. However, the CDC said a 2.3.2.1 vaccine virus candidate has already been created to allow rapid vaccine production if the virus changes to become a threat to humans. Also yesterday, the European Centre for Disease Prevention and Control (ECDC) issued a risk assessment on the emergence of a further evolved H5N1 lineage, stating that it does not change the current risk assessment to human health.
Sep 1 CDC "Have You Heard?" report
Sep 1 ECDC rapid risk assessment
Aug 29 CIDRAP News story

Egypt retools H5N1 prevention plans
Egypt's government is launching a new plan to fight the spread of H5N1 avian influenza, with new measures aimed at poultry producers and those who keep backyard poultry, Ahram Online, an English-language news site based in Cairo, reported yesterday. Osama Selim, who heads the country's veterinary services, said the plan encourages poultry breeders to sell frozen poultry at a lower cost to reduce the practice of buying live poultry. The plan also includes a public awareness campaign that highlights the risks of raising poultry inside homes. Egypt is one of a handful of countries where the H5N1 virus is endemic in poultry.
Sep 1 Ahram Online story

Study: Human H5N1 cases in Egypt follow weather-related cycle
Human cases of H5N1 avian flu in both Egypt and Indonesia appear to rise and fall in a cyclic pattern, and in Egypt the pattern coincides with meteorological conditions, according to a study by two epidemiologists at Columbia University in New York City. The researchers analyzed data from 135 Indonesian H5N1 cases from Jan 1, 2005, through May 1, 2008, and 50 Egyptian cases from Jan 1, 2006, through May 1, 2008, and compared them with local daily weather conditions. They used Fourier time series analysis to determine the seasonality of cases and associations between cases and weather. They found that Indonesian cases peaked every 1.67 years and Egyptian cases every 1.18 years. The cycle did not correspond to meteorological factors in Indonesia. In Egypt, however, cases peaked when precipitation was low and temperature, absolute humidity, and relative humidity were moderate. They point out that these variables contrast to conditions for optimal aerosol transmission, which are low temperatures and low humidity. The authors conclude, "Weather conditions coinciding with peak human H5N1 incidence in Egypt suggest that human infection may be occurring primarily via droplet transmission from close contact with infected poultry."
Sep 1 PLoS One study

Annual flu shots may lower cross-protection, say Dutch researchers
Annual flu vaccination appears to blunt the CD8+ T-cell response in children, which may interfere with cross-protection against influenza strains not targeted by the vaccine, according to a study by Dutch researchers in the Journal of Virology. Scientists studied blood samples from 27 unvaccinated children (median age, 6.0 years; range, 2-9) and 14 children with cystic fibrosis (CF) who received annual flu shots (median age, 6.6; range, 2-9). They found that the unvaccinated children had an age-dependent increase of virus-specific CD8+ T-cell response that was absent in the vaccinated group. The researchers had previously shown in animals that the decreased CD8+ T-cell response correlates with lower immunity against other strains of flu, or heterosubtypic immunity. They write that annual flu vaccination is effective but may have underappreciated drawbacks. "By no means, do we suggest halting annual vaccination of children, especially those at high risk for complications such as the CF patients. . . . However, long-term annual vaccination using inactivated vaccines may hamper the induction of cross-reactive CD8+ T cell responses by natural infections and thus may affect the induction of heterosubtypic immunity. This may render young children that have not been previously infected with an influenza virus more susceptible to infection with a pandemic influenza virus of a novel subtype." They also write that using CF patients rather than healthy vaccinated children should not affect the study's outcome.
Aug 31 J Virol abstract

Study finds differences in Southern Hemisphere H1N1 flu patterns
A study of 2009 H1N1 virus spread in Southern Hemisphere countries found that demographic differences may have made a difference and that overall transmissibility was low, at a level seen with seasonal flu. The group, from Imperial College London, compared transmission characteristics based on flu surveillance data from Argentina, Australia, Bolivia, Brazil, Chile, New Zealand, and South Africa, as well as Victoria state in Australia. Using modeling tools, they explored possible differences based on seasonality, population density, and demographics. They found that demographics partly played a role in differences between countries. Age-structured modeling suggested that children were more susceptible to the new virus than adults—countries that had a higher proportion of young people under age 20 had higher attack rates, a finding they said could result from likely cross-protection in adults due to earlier exposure to similar strains. Researchers suggested that the findings show the importance of modifying pandemic flu control policies on a country-by-country basis and that targeting children with vaccines in countries that have younger populations may be a useful strategy.
Sep 1 PLoS Pathogens study

FDA clears new CDC diagnostic flu test
The US Food and Drug Administration (FDA) has approved a new lab test developed by the CDC to detect seasonal flu and novel influenza A viruses, the CDC announced today in a press release. The CDC Human Influenza Virus Real-Time RT-PCR Diagnostic Panel is a three-module design that combines and streamlines two previously approved diagnostic test kits. The first distinguishes influenza A from influenza B, the second classifies influenza A by subtype, and the third detects H5N1 avian flu. Nancy Cox, PhD, director of the CDC's influenza division, said in the release that the modular design makes testing more efficient for labs, because it eliminates waste and offers more flexibility. The test is used with upper respiratory specimens and is the only in vitro kit for flu that is approved for testing lower respiratory specimens. The CDC kit will be given at no cost to qualified international public health laboratories. Dr Nicole Lurie, assistant secretary for preparedness and response in the Department of Health and Human Services, said that a national countermeasure review showed a need for better diagnostic tests. "In helping public health officials quickly identify seasonal flu as well as the flu viruses that could become pandemic, this kit can make a real difference."
Sep 2 CDC press release

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