May 27, 2011
H5N1 strains in Egypt show increased ability to bind to human cells
H5N1 avian influenza viruses in Egypt have branched into new sublineages and have shown a mutation that helps them bind more readily to human cell receptors in the lower respiratory tract, which may indicate an increased pandemic potential, according to a study published yesterday. Researchers from Egypt, Japan, and Thailand conducted a phylogenetic analysis of H5N1 viruses isolated from 2006 to 2009 in Egypt. Using reverse genetics, they found that several new sublineages have acquired an enhanced receptor-binding affinity of the viral hemagglutinin to alpha-2,6-linked sialic acid (SA), which is a receptor-binding trait of human influenza strains. The mutation was associated with increased attachment to and infectivity in the lower respiratory tract but not the larynx of humans and also demonstrated increased virulence in mice. The authors conclude, "Our findings suggested that emergence of new H5 sublineages with alpha-2,6 SA specificity caused a subsequent increase in human H5N1 influenza virus infections in Egypt, and provided data for understanding the virus's pandemic potential."
May 26 PLoS Pathog study
Chinese scientists find two novel H5N5 viruses in ducks
Chinese researchers today said they have identified two novel highly pathogenic H5N5 avian influenza reassortants during routine surveillance in domestic ducks. Writing in the June issue of Emerging Infectious Diseases, they said the two novel viruses were isolated from healthy mallard ducks at live poultry markets in eastern China in December 2008 and January 2009. During testing they were highly pathogenic in chickens and moderately pathogenic in mice. The investigators said the two new viruses are probably reassortants of Eurasian virus strains and that H5N1 subtypes could have provided their backbones. The group said the findings highlight the importance of ducks as vessels for creating new flu virus subtypes, and that, given free-range duck farming practices, the new strains could pose a threat to other poultry or to humans.
June Emerg Infect Dis study
Vietnam halts H5N1 poultry vaccination due to poor match
Vietnam's government announced yesterday that it has stopped its national program to immunize poultry against the H5N1 virus, because a new clade circulating in most of the country is ineffective against the vaccine, Reuters reported today. Vietnam's animal health department said the vaccine supplies ordered from China do not work against the new clade, which is circulating in northern, coastal, central, and Central Highlands areas. The older clade is still circulating in southern provinces, it said. Vietnam is one of a handful of countries in which H5N1 virus is endemic in poultry. Some endemic countries use the vaccine to contain the virus, but its use is controversial, because asymptomatic infections can spread when vaccination programs aren't adequately monitored.
May 27 Reuters story
Experts say flu shot is best hedge over uncertainty of duration of immunity
Next season's flu vaccine will contain the same three strains as this season, which has influenza experts fielding questions about whether currently vaccinated people need to be immunized in the fall. Experts say vaccine production can drop off quickly for frail and older people, but the scientific data on how long the flu vaccine protects younger healthy populations are unclear, the Associated Press (AP) reported today. The last time two consecutive flu seasons had a vaccine with the same three strains was between 2002 and 2004. Nancy Cox, MD, who leads the flu division at the US Centers for Disease Control and Prevention (CDC), said that some studies suggest immunity that wanes over time isn't strong enough to protect against flu. CDC officials have suggested that yearly vaccination can provide a hedge against the efficacy of existing vaccines, which is only about 70%, even when the vaccine is a good match with circulating strains. John Treanor, MD, a virologist at the University of Rochester School of Medicine, told the AP that experts don't have a clear picture of how long flu vaccine protection lasts. The CDC says yearly vaccination will offer the best protection. Flu vaccine manufacturers recently predicted that they will make a record number of doses for the upcoming season, between 166 million and 173 million.
US flu activity fades in season's final update
In its last weekly flu report of the season, the CDC said that most activity indicators continued to tail off, except for the percentage of deaths from pneumonia and flu, which rose slightly above the epidemic threshold. The percentage of doctors visits for flu-like illnesses remained at a level typical for summer months, and the percentage of respiratory specimens that tested positive for flu continued to decline. No pediatric deaths were reported, holding the season's total at 105. The overall percentage of deaths from flu and pneumonia increased slightly, from 7.3% to 7.4%, putting it slightly above the epidemic threshold. CDC officials have said that flu deaths can sometimes lag other indicators. No states reported widespread, regional, or local geographic spread. Sporadic activity was reported by Puerto Rico and 21 states, which is six fewer states than the previous week. The CDC said it will publish its first weekly report for the 2011-12 flu season on Oct 14.
May 27 CDC weekly flu surveillance report
Study: HIV does not raise risk of severe H1N1 illness
People with HIV fared no worse than others during the 2009 H1N1 influenza pandemic, according to a retrospective study in the June issue of Emerging Infectious Diseases. Researchers analyzed data from 23 patients at a Seattle medical center who had lab-confirmed 2009 H1N1, 8 of whom required hospitalization. The 8 patients received therapy for a median of 6 days (range, 1-22), and 2 of them (25%) died. "Our findings are similar to those reported by others, suggesting that HIV infection alone does not appear to be a risk factor for severe pandemic (H1N1) 2009, provided that patients are not severely immunocompromised, do not have other risk factors associated with poor outcomes, and are treated for influenza soon after signs and symptoms develop," the authors write.
June Emerg Infect Dis report
