The blazing sun is your best bet in the fight against swine flu, say experts.

A temperature of 37 to 38 degrees Celsius makes viruses like H1N1 inactive, raising hope that the scourge that has claimed eight lives in Bengal will disappear by itself once the mercury begins to soar and conditions become drier.

On Sunday, 16 new cases of swine flu were reported, most of them from in and around Calcutta, health department officials said. The number of people in Bengal diagnosed with swine flu stands at 131.

"The incidence of swine flu is likely to drop as the temperature rises. At 37 or 38 degrees Celsius, the virus loses its potency. At lower temperatures, it can survive outside the body of the host for two to three hours. But when the weather is hot and dry, H1N1 can't survive for more than a few minutes," a veteran virologist said.

The day temperature in Calcutta has been in the range of 33 to 34 degrees Celsius over the past couple of days and is expected to rise as March progresses. "Studies have shown that high temperature and dry weather kill microbes, including the H1N1 virus. They lose potency and cannot reproduce rapidly," A.K. Mishra, former director of the National Institute of Virology in Pune, told Metro.

The average maximum temperature in Calcutta in March is 33.5 degrees Celsius but the mercury does shoot up far beyond that in phases. Last year, the maximum temperature climbed beyond 35 degrees Celsius after March 15. By the end of the month, it was nudging 40 degrees Celsius.

H1N1, which is a kind of influenza virus, spreads mainly in two ways. It becomes airborne in the form of droplets when an infected person sneezes, coughs or spits and enters a new host through the mouth, eyes or nose.

Another way it can spread is when the infected patient touches his eyes, mouth or nose and then passes the virus to an inanimate object like a doorknob or even a pen. When a non-infected person touches the same object and then the eyes or mouth, the virus enters its new host.

"For both these modes of transmission, the virus has to survive in the open environment till it can enter the body of a new host. Obviously, the longer it can survive in the open, more the chances of transmission. This time span is cut short when the temperature increases and that is why outbreaks of influenza die out in summer," said Amitava Nandi, a specialist in tropical and infectious diseases.

According to doctors, influenza viruses like H1N1 cannot survive in extreme cold either, which is why they thrive during the change of season or when the temperature fluctuates. It doesn't get very cold in these parts; so influenza peaks in the last phase of winter and continues till the onset of summer.

The incidence of influenza tends to increase during the change of seasons also because the region around the human throat is unable to maintain a stable temperature. "The upper respiratory tract maintains a certain temperature that kills viruses entering the body through the mouth and nose. This is the body's first line of defence against viruses. But it tends to fail during change of season," Nandi said.