virus has made an appearance in Mumbai. A six-year-boy from Mulund tested positive for the virus that claimed several lives during and after the 2009 pandemic, and still continues to haunt neighbouring Pune.

The virus had remained 'underground' for the better part of 2011, but suddenly struck Pune in March this year killing five and affecting 95 people in a span of a few weeks, rekindling fears of a possible resurgence in Mumbai, too.

The six-year-boy tested positive for the virus two days ago, and is still in a Mulund hospital where doctors are monitoring his vitals. Executive health officer Dr Anil Bandivadekar confirmed the case, but said it is not an indicator that the virus is making a comeback in the city. "The patient has already been started on Tamiflu, and doctors have told us that he is stable. We will be monitoring his condition," he said declining to reveal the boy's name or the hospital he is undergoing treatment in.

In Mumbai, the virus was relatively inactive for almost a year: The last two cases recorded were in June 2011 when a 37-year-old woman from Chandivli and a three-year-old girl from Tardeo tested positive for the virus. The last death was recorded in July 2010.

But ever since the surge of positive cases in Pune, Mumbai doctors have been advising patients to get tested for H1N1. From one or two samples in a period of three months or more, laboratories are suddenly getting more samples. While health officials did not comment on the number of samples they have been receiving since the outbreak in Pune, private labs put the figure to a little more than 20 since the beginning of March.

Dr Simi Bhatia, lab director of Super Religare Laboratories Limited, said: "Of the 20 samples tested in March, one from Mulund tested positive for H1N1." The lab also tested 167 samples from Pune in March of which 37 tested positive.

Doctors who are advising citizens to take precautionary measures are also referring patients Kasturba Hospital for Infectious Diseases-a nodal centre for testing and treatment.

Bandivadekar said six people have been referred to Kasturba so far this month. "All the six patients have tested negative. One of the patients was referred from Saifee Hospital, and another three with travel history to Pune were referred from Parel's KEM Hospital," he said, adding that it showed the city physicians were alert about the possible threat. "Upper respiratory tract infection is quite common now. But, we are alert and have enough stock of Tamiflu."

Testing, however, holds little relevance, say experts as many people could be carriers of the virus but not suffer from the symptoms.

Director of Haffkine Institute Dr Abhay Chaudhary said, "Influenza or influenza-like illness is common in this season and the extended winter only made it worse. But H1N1 is more or less like other forms of seasonal virus circulating in the air now," he said. Chaudhary also believes that a large section of the population has developed immunity after the pandemic. "With mercury rising in the city, the chance of the virus creating havoc is minimal. But we have to remain alert. We have to keep in mind that