'Avian flu can turn into human contagion'

Updated on Feb 06, 2008 12:25 PM IST
Avian flu was a disease of birds but it started affecting humans as it changed character.
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IANS | ByJeevan Mathew Kurian, Kozhikode

Medical experts feel that there is a possibility of avian flu becoming a human contagion.

There is a fair chance that the avian flu virus might mutate and become a human virus, says Udaya B.S. Prakash, a pulmonologist with Mayo Clinic of Minnesota in the US.

"The influenza started off as a disease of the pigs, it was not a human disease. Eventually, it spread to humans, who became carriers of the disease," Prakash told IANS.

Prakash was in Kozhikode to attend a national conference organised by the Indian Association for Bronchology.

Prakash said it is a difficult task to develop a vaccine against avian flu. "The problem with the influenza group of viruses is that they mutate frequently. They change their behaviour making it difficult to develop a vaccine against the disease," he said.

"The influenza group of viruses is known for its unstable character. They easily adapt to new species if they are allowed to propagate into a species," said E. Sreekumar, a scientist at the Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram.

Avian flu was a disease of birds, Sreekumar said. But it started affecting humans as it changed character. If the virus is allowed to propagate in humans, it can change its character again to become human virus.

Prakash said every year researchers have to make a new batch of influenza vaccine in the US as the virus undergoes "antigenic shift". The antigens and proteins in viruses change making old vaccines ineffective against a new form of influenza.

"The same thing probably applies to avian flu. Even if you make a vaccine, it has to be repeatedly prepared for human protection. It will be very difficult to produce vaccine in mass quantities on a frequent basis," he said.

The influenza viruses are RNA viruses. They have less fidelity while they replicate. During replication, errors enter their genetic material. When these errors accumulate, the virus gets a new character and become capable to infect new species.

Treating avian flu remains a difficult challenge because there are no specific drugs.

"There are some antiviral drugs like Tamiflu. We use the drugs in those who have been exposed to influenza if they had not had the vaccine ... But they really haven't developed a suitable drug to use against avian flu," Prakash said.

The more important thing is to isolate the source of infection. "If we can identify a location where infection appeared, what is important is to eradicate the disease in that area; by destroying the affected birds, if necessary," he said.

Prakash said the fight against the disease has to be worldwide to control the avian flu effectively. "Treating just one country will not solve the problem as it can again come back from another country," he said.

To work effectively against the disease, it is important to learn about the behaviour of the disease.

"On some days you worry about it because the disease is affecting many countries. Then you won't hear about it for a few months before another outbreak. The difficulty is to really understand the behaviour of the disease and why it is not spreading as rapidly as we suspected earlier," Prakash added.

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