WHO Reports Bird Flu May Be Transmitted Through Dust And Surfaces
The World Health Organization (WHO) released a report today suggesting the H5N1 bird flu virus may be transmitted to humans through contaminated surfaces and dust.
The organization reported that although most cases of H5N1 infection are passed directly from birds to people, researchers found that over one in four infected patients have no known source of the disease.
“In one quarter or more of patients with the influenza A (H5N1) virus infection, the source of exposure is unclear, and environment-to-human transmission remains possible,” the report said.
Plausible transmission routes include contact with contaminated objects carrying the virus, or with fertilizer containing feces from infected poultry, or inhalation of aerosolized virus, the report said.
In reaching their conclusion, the researchers reviewed all known human cases of H5N1 infections and determined that 25% were without explanation for a cause. Since 2003, H5N1 infections have occurred in 350 people in 14 countries, with 217 deaths.
H5N1 is endemic in birds in parts of Indonesia, Africa and the Middle East, and is often found in European birds. However, despite widespread exposure to these infected birds, H5N1 infections are rare. But researchers worry about the possibility that the virus will mutate into a strain easily passed from person to person, causing a pandemic that could potentially kill millions within a few months.
Handling sick or dead poultry during the week before the onset of illness is the most common risk factor, and most patients have acquired the H5N1 infection from poultry raised inside or outside their houses. Direct human-to-human transmission of the infection is rare, and always involves intimate physical contact.
Clinical features of a H5N1 infection usually include severe pneumonia that often progresses rapidly to an acute respiratory distress syndrome. Very rarely, if ever, does the disease occur without symptoms. The median age of patients with the infection is 18 years, with 90% of patients 40 years of age or younger, according to the WHO report.
“After exposure to infected poultry, the incubation period generally appears to be 7 days or less, and in many cases this period is 2 to 5 days,” the report said.
The time from onset of illness to presentation of symptoms is around 4 days, and the median time from the onset of illness to death was 9 days. 61% of those infected have died of the illness.
Treatment with antiviral drugs, such as Tamiflu, can prevent some deaths from the disease.
The research was led by WHO’s Dr. Frederick Hayden, and the report was published in the New England Journal of Medicine. A free text version of the report can be viewed on the Journal’s Web site at http://content.nejm.org/cgi/content/full/358/3/261.