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Thursday, 13 January 2011






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Confronting emerging infection threat

Humans have been badly affected by epidemics throughout history. People are more interconnected as they travel frequently. Changes in society bring more infectious diseases as viruses can spread very quickly

Professor Malik Peiris

The lecture Confronting the threat of new emerging infection, one of a series called Meeting of Minds was organized by the University of Hong Kong. It is trying to bring scientists from Hong Kong to talk to students, predominantly those who are beginning their university careers and high school students; to stimulate them with what research is and what science is, so that some of them might be motivated to take up science and research as a career.

Supernatural forces

Epidemics throughout history have been very frightening. For many years people thought these were acts from supernatural forces.

The Black Death came to England and wiped out almost one third of the population and in similar parts of Europe. It was a horrible disease.

“I started life as a microbiologist here in Sri Lanka and the first major epidemic I confronted was in Sri Lanka. At that time I was working in Peradeniya University in 1985. A major outbreak of Encephalitis was recorded in Anuradhapura in October 1985. It is a brain fever; a brain infection with about 10 percent deaths and even some of those who recover have paralysis for life”, said Professor Malik Peiris of the Microbiology Department, University of Hong Kong in his address at the BMICH.

Wild birds

Normally it is one case in hospital in every three or four months. To see 500 in three months in one hospital is absolutely incredible.

So we at Peradeniya diagnosed the cause of Japanese Encephalitis. But then the question came up; why did this thing happen suddenly out of the blue? Because before this the disease had been present in Sri Lanka occasionally but never a big outbreak. So how do you tackle such a situation?

Missing link

“The information available suggested that the virus itself is present in wild birds and transmitted from mosquitoes from bird to bird and as long as it stays there then it doesn’t do any harm. Sometimes it gets transmitted occasionally from mosquitoes to pigs and then pigs to humans. But why 500 cases in that particular hospital?,” stated Peiris.

What is the trigger? What caused this? Is it a mutation in the Virus? Could it be a change from mosquito numbers or the type of mosquitoe spreading the disease? Maybe it is a different animal and not a pig amplifying this disease.

So those were the possibilities Professor Peiris and his team thought about.

“We looked at the Virus and it was no different to the virus we found in the previous years in Sri Lanka. So no real mutation in the virus. Then we collected mosquitoes and hung mosquito traps in pigpens at night.

“There were more than 10,000 mosquitoes caught in the trap. So we tested these mosquitoes and we worked out what mosquitoes were carrying this. It was the typical mosquito, so there was no difference there,” pointed out Professor Peiris.

Poor rice farmer

Then the team looked at the pigs, taking blood samples and in the course of the outbreak they found pigs get infected before the humans and this is the typical pattern. The virus is going from birds to mosquitoes to pigs, then pigs and mosquitoes to humans.

They then found out that that the problem lay with the rice farmers. Rice farmers have a tough life, they don’t have a huge amount of money and the logical thing was to supplement the income of the poor rice farmer by providing them with back yard pigs as an additional protein source.

“What it did was to set the match to the conditions that were perfect for Japanese Encephalitis transmission.

Rice Paddies, thousand’s of mosquitoes, the birds were there in the same environment and the pigs were the missing link. That missing link become a reality and then you have this huge outbreak,” concluded Professor Peiris.

Swine flu

This shows how a change in an ecological equation, maybe for very good intentions but can actually lead to many sad outcomes.

“We really have to be conscious of infectious disease because of the changes in society. We are becoming much more interconnected. There is much more travel. Any infection that breaks out anywhere can spread across the world in two weeks,” said Professor Peiris.

So the studies they did with the recent swine flu. Swine flu was detected in April 2009 in Mexico. By October 2009 from studies we had done, half of the children in Hong Kong were infected by that time. So within five months of hearing about this new virus - it had spread so rapidly all across the world. Around 50 percent of children were infected but they were very lucky that as a virus it was relatively mild - it is an influenza virus called Swine Flu H1N1.

“So I think this just shows how quickly a new virus can emerge and spread very quickly around the world,” said Professor Peiris.

Swine Flu emerged in 2009. How do these pandemics emerge? We understood this only 30 years ago. When the influenza virus infects humans it goes on year after year by changing slightly, doing so it can continue to circulate in the human population. But after 20 or 30 years it is a completely new virus. And then the human immune system completely doesn’t see it. So it can spread very rapidly. It was realized that what was happening is that Alien influenza virus genes are being picked up by human influenza virus’ becoming hybrid, mixing alien and human genes giving rise to a complete change in the outer core leading to a pandemic.


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