Bird flu spread to humans more easily than thought

NEW YORK (Reuters Health) – Although human bird flu infection is believed to be a rare, life-threatening disease, a study in Vietnam suggests that the infection rate may be higher than was previously thought, often causing relatively mild respiratory symptoms.

In a report in the Archives of Internal Medicine, Dr. Anna Thorson and her associates note that high death rates are derived from avian flu patients admitted to hospitals in major cities. The researchers believe that the true occurrence and mortality rates are unknown, since there have been no studies assessing exposure to the virus and disease in a population-based setting.

The authors conducted a survey in Bavi, a rural district in Vietnam in which there had been confirmed outbreaks of severe bird flu among poultry. Included in the study were 11,942 households with 45,478 inhabitants, interviewed between April 1 and June 30, 2000.

Subjects were asked about the occurrence of cough and fever during the previous six months as well as contact with poultry. A total of 8,149 reported having had a flu-like illness.

Having contact with sick or dead poultry was strongly associated with flu-like-illness. Among young and middle-aged adults direct contact with such poultry more than doubled the risk of a flu-like illness.

Thorson, from the Karolinska Institute in Stockholm, and her team estimate that between 650 and 750 cases could be attributed to direct contact with sick or dead poultry.

SOURCE: Archives of Internal Medicine, January 9, 2006.