A few facts from the April 18 CDC Update:
As of April 15, 2005, there have been 88 human cases of avian influenza A (H5N1) in Vietnam(68), Thailand(17), and Cambodia(3) resulting in 51 deaths.
The avian influenza A (H5N1) epizootic outbreak in Asia is not expected to diminish significantly in the short term. It is likely that H5N1 infection among birds has become endemic to the region and that human infections will continue to occur. So far, no sustained human-to-human transmission of the H5N1 virus has been identified, and no evidence for genetic reassortment between human and avian influenza virus genes has been found; however, the epizootic outbreak in Asia poses an important public health threat.
Recent research findings give further cause for concern. New research suggests that currently circulating strains of H5 viruses are becoming more capable of causing disease (pathogenic) for mammals than earlier H5 viruses and are becoming more widespread in birds in the region. One study found that ducks infected with H5N1 are now shedding more virus for longer periods of time without showing any symptoms of illness. This has implications for the role of ducks in transmitting disease to other birds and possibly to humans as well. Additionally, other findings have documented H5 infection among pigs in China and H5 infection in felines (experimental infection in housecats in the Netherlands and isolation of H5N1 viruses from infected tigers and leopards in Thailand), suggesting that cats could host or transmit the infection. These finding are particularly worrisome in light of the fact that reassortment of avian influenza genomes is most likely to occur when these viruses demonstrate a capacity to infect multiple species, as is now the case in Asia.
Notable findings of epidemiological investigations of human H5N1 cases in Vietnam during 2005 have suggested transmission of H5N1 viruses to two persons through consumption of uncooked duck blood. Possible person-to-person transmission of H5N1 viruses is being investigated in several clusters of cases in Vietnam.