The first human case of bird influenza in seven years has been diagnosed in Hong Kong. A 59-year-old woman was hospitalized in serious condition after a trip to mainland China. Her illness was diagnosed as influenza A (H5), a variant of bird flu. It was unclear where she had contracted the disease.
Avian influenza does not normally infect species other than birds and pigs. But humans came down with bird flu in Hong Kong in 1997, with the H5N1 strain infecting 18 humans, six of whom died. Then, people became infected after coming into close contact with live infected poultry. Genetic studies showed the virus had jumped from birds to humans, and caused severe illness with high mortality.
Infection triggers a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in epidemics. In severe cases, the flu is characterized by a sudden onset of severe illness, and rapid death, with a mortality that can approach 100 percent.