(HealthDay News) – The fatality risk of human infection with avian influenza H7N9 is 36% among people of all ages, and there are epidemiological differences in cases with H7N9 and H5N1, according to two studies published online June 24 in The Lancet.

Hongjie Yu, MD, from the Chinese Center for Disease Control and Prevention in Beijing, and colleagues assessed the clinical severity of human infections with H7N9 virus using data from an integrated database. Of the 123 patients with laboratory-confirmed avian influenza A H7N9 virus infections who were admitted to the hospital, the researchers found that by May 28, 2013, 30% had died and 56% had recovered. On admission to the hospital the estimated fatality risk for all ages was 36%.

Benjamin J. Cowling, PhD, from the University of Hong Kong, and colleagues compared epidemiological characteristics of laboratory-confirmed cases of influenza H7N9 (130 patients) and influenza H5N1 (43 patients) that were reported to the Chinese Center for Disease Control and Prevention. The researchers found that the median age of infection was 62 years for H7N9 and 26 years for H5N1. In urban areas, 74% of cases were men, whereas in rural areas the proportions were 62% for H7N9 and 33% for H5N1. Recent exposure to poultry was reported by 75% and 71%, respectively. On admission to the hospital the mortality risk was 36% and 70%, respectively.

“Although both viruses are of avian origin, and neither has yet acquired the ability for sustained human-to-human transmission, differences exist in their epidemiology,” Cowling and colleagues write.

Two authors from both studies disclosed financial ties to MedImmune and Crucell.

Abstract – Yu

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Abstract – Cowling

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