The increasing number of swine flu cases in the country -- 56 so far is -- is worrying authorities. And now that the virus has spread to smaller towns and as monsoon hit the country, patients with respiratory problems like asthma need to be extra careful.

The swine flu is slowly spreading out of the metros and going interior. New cases have come up in Gurdaspur, Amritsar, Kochi, Calicut (Kerala), Pune and Gurgaon.

Doctors say the checks at smaller international airports may not be very strict. Also, as the passengers from abroad land in the metros and travel to their hometowns in trains or buses, they may be taking the flu with them.

"It is more difficult to contact passengers on trains than airplanes. But there have been two cases in which patients were travelling on train and with help from the Rail Ministry we have been able to trace the passengers who came in contact," Health Secretary Vineet Chaudhary said.

Vigil has been stepped in smaller towns, as there is fear the H1N1 virus could spread faster in the monsoon months.

"We have deployed more doctors during night time when more number of flights arrive from Gulf countries, which have a huge population in Kerala," said Anil Kumar, Additional Director, Health.

There are not many secondary cases in India yet, but the Health ministry warns that the number may rise now that monsoon has hit the country. And patients with respiratory problems like asthma need to be extra careful.