February 19, 2010

Bird flu virus mutation shadows vaccine effectiveness

A genetically mutated bird flu virus may have been responsible for a string of deadly outbreaks in bird populations over the past two years.

Virologist I Gusti Ngurah Mahardhika from Indonesia's Udayana University, warned that the new virus could be more lethal than its ancestors H5N1 should it infect humans.

He said the government's vaccination programme with a large number of poultry farms in the past few years may backfire because the mutation was partly suspected to have been caused by an outdated vaccine.

Old vaccine seed cannot stop the new virus, he said.

Isolated virus samples taken from already vaccinated farms in Java, Sumatra, Bali and Sulawesi from 2008 to 2009 were compared with samples from their ancestor H5N1 virus taken from Legok, Banten, in 2003.

The study revealed genetic differences of up to 8.7% from the ancestor virus, he said.

The Legok virus is still being used by most local vaccine producers as the vaccine seed and the recent mutations may mean the seed virus is outdated. The genetic differences in the virus samples are mostly represented by changes in the acid composition, or RNA (ribonucleic acid), which have never been found in the 2003 samples.

Genetic mutations could be triggered by either natural causes or vaccine resistance, but in this case, the changes pointed more to the possibility of vaccine resistance, according to Mahardhika.

Indonesia has been hit hard by the spread of bird flu, both in humans and poultry. The first outbreaks in bird populations were reported in 2003 with the virus spreading to humans two years later, killing at least 125 people.

Memed Zoelkarnain, spokesman for the National Commission for Avian Influenza and Pandemic Prevention, said the findings must be studied further so that the public would not be alarmed. He also emphasised that the findings are preliminary.

Memed added that only a few local vaccine producers in Indonesia used the 2003 vaccine seed.