Genetic comparison of H9N2 AI viruses isolated in Jordan in 2003

SUMMARY. During the 1990s, several outbreaks of avian influenza (AI), caused by viruses of the H9N2 subtype, were reported in poultry in various parts of the world. Currently, this infection seems to be endemic in poultry in the Middle and Far East, and the extensive circulation of H9N2 in poultry represents a risk factor for infection of humans, because viruses of this subtype have been sporadically introduced into the human population. Little is known about the gene constellation of the H9N2 viruses that are currently circulating in the Middle East; thus, gene sequences of eight IA viruses of the H9N2 subtype isolated in Jordan in 2003 from poultry were analyzed. The results of this investigation show that all eight Jordanian isolates are closely related to each other and to other H9N2 isolates from the Middle East. Seven of eight genes of the Jordanian strains show a percentage of homology not higher than 95% with the genes of two H9N2 strains, A/HK/1073/99 and A/HK/1074/99, isolated from humans in Hong Kong. The M gene is more closely related to the corresponding gene of the two H9N2 human isolates from Hong Kong (97.7-98.2% homology). This homology suggests that the M gene of the Jordanian and human Hong Kong strains could derive from a common ancestor.