Kids, pregnant women, senior citizens and patients with heart diseases are particularly at risk. File pics for representation

It was a feverish Friday in Mumbai, with as many as 18 cases of swine flu - a record high - registered in a single day. What has the city's doctors breaking into a sweat is also the host of new symptoms - high fever, loose motions - that patients are complaining of.

Doctors don't know what to make of this unseasonable outbreak of swine flu cases – normally, September-October is when people fall prey to the virus. This year, however, the bug has come several months early and seems to have become nearly 100 times stronger.