Influenza viruses are classified according to the combination of two types of proteins found on the virus cell surface. Different combinations of the 16 types of hemagglutinin (H) protein and nine types of neuraminidase (N) protein form a large number of influenza viruses for which birds are the natural hosts.
New, often more dangerous flu strains develop when the H and N combinations change and combine with other genes from circulating influenza viruses. When the genes of a human or swine influenza mix with an avian variety, a highly pathogenic human flu likely will result, Mittal said.
The first bird-to-human H5N1 case was recorded in 1997 in Hong Kong. The deadly virus has been documented in more than 60 countries, according to the World Health Organization (WHO). Though it mainly has struck wild birds and poultry, there have been more than 300 human cases in 14 countries in the past decade with a 60 percent fatality rate. Most of the human cases have occurred in people who live and work closely with their poultry, but a few cases have been documented of the disease spreading from person to person.
In a typical case, WHO this week reported the most recent fatality - the death of a 30-year-old Egyptian woman who became ill on April 2 after handling sick birds. She did not respond to the antiviral treatment Tamiflu, which can be given after contact with a flu carrier.
The next step in the bird flu vaccine project will be to test the vaccine on new viruses that are appearing, Mittal said.
The scientific team's vaccine work is being developed by PaxVax Inc., which has licensed the technology. Mittal is a scientific adviser for the company but has no financial stake in the com
|Contact: Susan A. Steeves|