NEWS SCAN: H5N1 burden in Egypt, flu in US songbirds, California pertussis epidemic, vaccine-derived poliovirus

Jun 24, 2010

Women bear heaviest H5N1 burden in Egypt
An analysis of human cases of H5N1 avian influenza in Egypt from March 2006 to March 2009 revealed that women were at highest risk for infection and death. Of 6,355 suspected cases reported during the 3 years, 63 patients (1%) tested positive, and 24 of them (38%) died, according to the report by Egyptian and US researchers in Emerging Infectious Diseases (EID). Females aged 15 years and older accounted for 38% of cases and 83% of deaths, The case-fatality rate (CFR) in women was 52.5%, probably at least in part because of delays in hospitalization and antiviral treatment. Children (younger than 15) accounted for 54% of cases but only 8% of deaths. The researchers found that children were hospitalized earlier in the course of illness, were more likely to receive oseltamivir within the first 2 days, and appeared to be less sick than adults. The lower CFR in Egypt than in other countries affected by H5N1, including Indonesia, Vietnam, and China, has prompted speculation about a less virulent H5N1 strain. But the authors suggest that the lower death rate may be explained by prompt treatment of children. All but two case-patients reported exposure to probably infected domestic poultry, and no cases of human-to-human transmission were identified. More than 5,000 asymptomatic people who had been exposed to case-patients or infected poultry were tested, with no positive results.
July EID report

Study: US songbirds can harbor avian flu
In addition to waterfowl, some songbird species are avian influenza reservoirs on the US mainland, according to a study published in BMC Infectious Diseases. Since the 1970s, waterfowl have been known to harbor avian flu strains, but researchers didn't know much about the status of songbirds. The group analyzed cloacal samples from 225 birds, 152 of them songbird species, in 41 states between 2005 and 2008. Using a model that included environmental and geographic variables, they found that flu prevalence in songbirds was greater than in eight other types of birds, with modeling suggesting that the Great Plains and the Pacific Northwest are high-risk areas for avian influenza. The group linked harvested cropland and first snow-free day of the year to higher risk levels.
Jun 23 BMC Infect Dis abstract

California sounds pertussis warning
California's public health director yesterday that the state was experiencing a whooping cough (pertussis) epidemic, its worst in 50 years. As of Jun 15, California had recorded 910 cases, a fourfold increase from last year, according to a statement from the California Department of Public Health (CDPH). Local health departments are investigating 600 more possible cases. Five infants, all under 3 months of age, have died from the disease. The CDPH said pertussis outbreaks are cyclical, with cases peaking every 2 to 5 years. It added that incompletely immunized infants are most vulnerable. In California, Hispanic babies appear to be particularly at risk; since 1998, 80% of the state's infant pertussis deaths have been in that ethnic group. Dr Gilberto Chavez, with the CDPH's Center for Infectious Disease, said all of this year's infant deaths were among Hispanic groups, the New York Times reported. He said lack of immunization information in agricultural regions may be a contributing factor and that the state's highest number of cases is located in Fresno County in the Central Valley growing region. Health officials are urging all Californians to be vaccinated and are providing vaccine free of charge to hospitals and urging vaccination of new mothers and fathers before sending newborns home.
Jun 23 CDPH statement
Jun 23 New York Times story

Study compares effects of vaccine-derived and wild polioviruses in Nigeria
The attack rates and illness severity associated with circulating vaccine-derived polioviruses (cVDPVs) and wild-type polioviruses (WPVs) have been similar in Nigeria in recent years, according to an analysis published by the New England Journal of Medicine (NEJM). An international team of researchers studied data on type 2 cVDPV, type 1 WPV, and type 3 WPV gathered in routine surveillance from 2005 through the first half of 2009. There were 278 cases of type 2 cVDPV, for an estimated average annual clinical attack rate of 2.7 cases per 100,000 children under age 5. The researchers counted 2,323 cases of type 1 WPV, signaling a clinical attack rate of 6.8, and 1,059 cases of type 3 WPV, for an attack rate of 4.0. The estimated effectiveness of trivalent oral polio vaccine against paralysis from type 2 cVDPV was substantially higher than its effectives against types 1 and 3 WPV (38% vs 13% vs 20%). "International planning for the management of the risk of WPV, both before and after eradication, must include scenarios in which equally virulent and pathogenic cVDPVs could emerge," the report states.
Jun 24 NEJM abstract

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