New Delhi, Aug 4 - A day after a 14-year-old schoolgirl died in Pune of swine flu, doctors and experts Tuesday warned that the H1N1 infections in the country could increase as the virus spreads faster during the monsoon and winter.

Experts said people need to be more vigilant and take precautions as the swine flu virus has entered the country.

'Surveillance and screening has to be given high priority. The virus has been mild so far, but it is a well-known fact that it could change its behaviour. And if it changes, then the virus could be more virulent,' Randeep Guleria, head of medicine at the All India Institute of Medical Sciences (AIIMS), told IANS.

'The swine flu virus can spread rapidly during monsoon and winter months. Therefore, we could see more infections in the coming months. It could be serious,' he added.

However, he pointed out that people need not panic due to the death of a girl in Pune which was caused by 'delayed treatment'.

Rida Shaikh, 14, died Monday evening in a Pune private hospital - the first swine flu death in the country. She succumbed to the disease as she got the correct treatment 'too late'.

Guleria warned that there were chances the virus could spread in 'clusters'.

'People need to be more vigilant as the virus has entered the country. The chances are now that it would spread in a community or in clusters like schools or localities,' he added.

The professor said if people living in a community or a cluster exhibit similar illness symptoms, they should be screened or tested for the virus so that the anti-flu Tamiflu medicine can be given in time.

S. Chatterjee, senior consultant in the internal medicine department in Indraprastha Apollo Hospital, agreed with Guleria, saying there is a 'possibility that the second strain of virus might turn lethal in winter'.

'The best thing is to follow precautions and early diagnosis of flu,' he said.

According to Chatterjee, since there is a possibility of the number of cases rising, the government should identify private hospitals for treatment.

'Government hospitals alone cannot handle the swine flu cases if there is an outbreak, and so the government should identify private hospitals to handle such cases,' he said.

Sunil Kumar Lal, assistant scientist at the International Centre for Genetic Engineering and Biotechnology (ICGEB), said: 'There is a possibility of the virus mutating as it circulates.