While the country gears up to face yet another swine flu outbreak, a research paper published in the Indian Journal of Medical Research has knocked the bottom out of the hitherto held notion that swine flu was a human-to-human infection since Indian pigs were free from the deadly influenza A H1N1 virus.

For the first time, a team of researchers headed by Dr K Nagarajan of the Tamil Nadu Veterinary and Animal Sciences University, Chennai, has detected in pigs a virus sharing close homology with that of the one that caused the 2009 swine flu pandemic.

The study titled Influenza A H1N1 virus in Indian pigs & its genetic relatedness with pandemic human influenza A 2009 H1N1, published in the August issue of the journal, said: "It is not known since when this virus has been circulating among Indian pigs."

The report concludes with a scary remark: "Dual infection in pigs may result in a new reassortment with high transmissibility and case fatality in human beings. To avert such a situation, intensive surveillance of humans, pigs and poultry for influenza virus infections is needed."

The team investigated disease outbreaks with clinical history suggestive for swine influenza reported by owners of pig farms in Uttar Pradesh. After collecting blood samples and nasal and ocular swabs from the pigs, the team conducted the research at the National CSF Referral Laboratory in Izatnagar in Uttar Pradesh and found that there was a close genetic relationship between the virus found in the pigs and the one that caused swine flu last year.

However, Dr Nagarajan is not sure if the pigs were infected by humans or by any other means. In the case of pig farms in Uttar Pradesh, no humans picked up the infection last year though many of them had been working closely with the infected animals.

But that should not be a reason for complacency, he warns, since there had been cases in countries like US and Mexico where the humans had been infected by ailing pigs.