Bird Flu More Prevalent But Fewer Dying

H5N1 Influenza now more common but less fatal

/ Author:  / Reviewed by: Chris Galloway, M.D.

(RxWiki News) Bird flu may not be as fatal as previously believed, though new evidence suggests that a larger-than-expected number of individuals have been exposed to minor bird flu illnesses.

A larger than expected percentage of individuals have been exposed to minor bird flu infections, also known as H5N1 influenza A.

Taia Wang, leader of the study and a microbiologist at the Mount Sinai School of Medicine, found that blood serum evidence indicates that 1 percent to 2 percent of more than 12,500 individuals studied had suffered from a previous bird flu infection, though most did not become ill.

Authors indicated that the World Health Organization's claim that the virus kills more than half of those infected appears to be an exaggeration. She believes the mortality rate may be inflated because minor cases were not accurately counted. WHO reports that fewer than 600 were infected with the virus. Only bird flu patients who die in a hospital are counted toward that total.

During the review study researchers collected evidence of antibodies of the virus from 12,677 Asians, Africans and Europeans that had participated in 27 studies between 1997 and 2009. Investigators estimated 1.2 percent of the participants survived mild cases of bird flu, suggesting that millions around the world have been infected with the virus.

However, not all scientists believe that WHO has overstated the deadliness of the virus. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, called H5N1 "a very dangerous virus."

"We believe that the assertion that the case-fatality rate of H5N1 influenza in humans may be overestimated is based on a flawed data analysis," he said.

The study was recently published in journal Science. Two additional studies regarding bird flu are pending publication in mBio, the journal of the American Society for Microbiology, because investigators were asked to withhold critical details in the interest of biosecurity.

Reviewed by: 
Review Date: 
February 23, 2012
Last Updated:
February 28, 2012