Robert Roos News Editor
Mar 19, 2009 (CIDRAP News) – Scientists who analyzed 67 H5N1 avian influenza viruses from across Africa report that the viruses fall into three distinct sublineages, or families, and that some have mutations that make them resistant to antiviral drugs.
The scientists also found that some of the African viruses have genetic markers that are characteristic of human flu viruses rather than avian strains, according to their report, published yesterday in the online journal PLoS One.
“These findings raise concern for the possible human health risk presented by viruses with these genetic properties and highlight the need for increased efforts to monitor the evolution of A/H5N1 viruses across the African continent,” says the report by a large international team of scientists. The group includes several from African countries and the UN Food and Agriculture Organization.
Lethal H5N1 viruses made their African debut on Nigerian poultry farms in January 2006, the report notes. Soon afterward the virus cropped up in Egypt, Niger, and Cameroon, and in April 2006 it was found in Sudan, Burkina Faso, Djibouti, and Ivory Coast. The virus surfaced in Ghana and Togo in mid-2007 and in Benin in December 2007.
All but two human cases of H5N1 disease in Africa have occurred in Egypt, whose official case count is 58, with 23 deaths. Nigeria and Djibouti have each had one human case.
Rapid spread of 3 sublineages
The scientists looked at 494 H5N1 gene sequences from 67 African isolates, including the complete hemagglutinin and neuraminidase gene segments, all collected between February 2006 and early 2008 and representing all 11 affected countries. The analysis also included hundreds of gene sequences from European and Middle Eastern H5N1 viruses.
The researchers determined that all the African viruses belong to clade 2.2 and are related to the H5N1 viruses that have been circulating throughout Europe, Russia, and the Middle East since late 2005. Clade 2.2 traces back to the outbreak of avian flu in thousands of migratory birds at China’s Qinghai Lake in the spring of 2005, the article notes.