Click to play videoNew Delhi: The 2009 H1N1 influenza virus is new, but flu pandemics are not. H1N1 Influenza A virus is the fourth big influenza pandemic of the century. From the past, we've learned that pandemics come in waves - spring and summer generally sees a mild wave, but they get more virulent by autumn or winter.
So does that hold true this time around?
Dean of Clinical Research Education and Management Academy (CREMA) at Mumbai, Dr SM Sapatnekar says. "One can't generalise pandemics. The swine flu pattern has been different till now, it's a more evolved pandemic. Think about SARS - how deadly it was, and killed so many people. It was predicted then that it would kill millions more, but then it suddenly died out. The avian flu too gripped the world a few years ago. For years scientists said it would become an outbreak in humans, but till date it hasn't.
The influenza virus is very unpredictable because it mutates drastically. History suggests that Influenza A pandemics come every 30 years or so and severe ones seem to hit every 100 years.
So while the 1918 Spanish flu killed somewhere between 20-50 million people and infected a third of the world's population, it died down as quickly as it erupted.
The 1957 H2N2 or Asian Flu killed 70,000 people in the first wave and about 2 million in the second wave, fading away only when 75 per cent of the world population developed resistance towards the virus.
And the last big pandemic, the 1968 Hong Kong Flu, killed nearly 1 million people worldwide over two years. It's H3N2 virus still circulates today.
"Viruses die down in two ways - either through herd immunity or the virus loses its bite. Herd immunity is when more and more people get infected. When the virus is new then everyone is susceptible, but not after people start developing resistance towards the pathogen. Also, the disease breaks out in clusters, so the virulence of the virus decreases in due course," says Dr Sapatnekar.
So when will we see the end of this pandemic? Doctors say that is hard to predict, but add that most flu viruses have historically only been wiped out when eight out of 10 people have been affected. However, pathogens are erratic and follow no set pattern.
They site the example of a broadly similar H1N1 strain which emerged in the US in 1976 and then vanished after killing just one person.
So while it's impossible for science to correctly predict the nature and course of the H1N1 virus - and keeping in mind the the fickleness of pathogens in India - it's best not to the panic. After all, if swine flu is taking three lives in a day, common flu kills around 572 a day.
(With inputs from Aruna Ramesh in Mumbai)
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