The state reported 18 swine flu casualties and 254 positive cases in August. The toll is considered the highest since April this year. Experts have advised people to exercise caution as there has been an increase in the H1N1 virus transmission.

"As many as 18 people succumbed to swine flu infection in August," state epidemiologist Pradip Awate told TOI on Sunday.

Fourteen casualties and 218 positive cases were registered in April when the H1N1 virus had reared its head across the state after a considerable gap. After that, the resurgence of the virus was seen in August. In the meantime, between May and July, the H1N1 virus transmission was on the lower side with a few couple of positive cases and sporadic deaths due to the contagion.

"In May, there were 29 positive cases and two deaths due to swine flu in Maharashtra. June saw 40 positive cases and zero death. The virus transmission started gaining grounds again from July, when 205 positive cases and eight deaths were registered. The transmission reached its peak in August with the highest number of deaths (18) and 254 positive cases," Awate said.

The symptoms of seasonal and pandemic H1N1 influenza include fever, cough, sore throat, runny or stuffy nose, body aches, headaches, chills and fatigue. Some may also have vomiting and diarrhea. Some people may be infected with the flu, including the pandemic H1N1, and have respiratory symptoms without a fever.

So far, it has been observed that certain medical conditions increase the risk of severe and fatal illness. These conditions include obesity, respiratory diseases – notably asthma – cardiovascular diseases, diabetes and immunosuppression, liver disorders, pregnancy, hypertension and neurological disorders.

In 2010, the World Health Organisation had warned of sporadic seasonal outbreaks of the disease due to changes in season. It had said this would happen for a couple of years till the virus dies down.