Experts in bioterrorism last week recommended that India expand its disease surveillance network and its ability to monitor bioterrorism. They want to ensure that bioterrorist attacks are not passed over as natural disease outbreaks or outbreaks of unknown origin, or classified as an emerging infectious disease.
There is no proof that biological warfare attacks have been carried out against India, but all the factors are very much in place, Colonel Anantasubramanian Nagendra, head of microbiology at the armed forces medical college in Pune, told a conference on pathogens of biological warfare at the National Institute of Communicable Diseases in New Delhi.
Terrorist incidents have occurred across India and insurgents are fighting in Kashmir, with the support of Pakistan and Osama bin Laden's terror network. “We have to wake up,” Colonel Nagendra said.
The threat of biological warfare has been engaging the attention of Indian defence and medical experts for a long time. During the Indo-Pakistan war of 1965, a scrub typhus outbreak in northeastern India came under suspicion. India's defence and intelligence outfits were alert to the outbreak of pneumonic plague—well known in biological warfare—in Surat and bubonic plague in Beed in 1994, which caused several deaths and sizeable economic loss.
Dr Kamal Datta, director of the National Institute of Communicable Diseases, alluded at the conference to some “suspicious” outbreaks, such as a 1996 outbreak of dengue in Delhi (10252 cases; 423 deaths), and the outbreak of unidentified encephalitis in Siliguri, eastern India, in February this year (66 cases; 45 deaths). Both outbreaks have baffled Indian researchers.
Molecular characterisation studies on the dengue-2 virus samples were done by researchers from the institute and from the All India Institute of Medical Sciences.
“We compared the 1996 samples with 1967 samples and found that there is roughly 10% divergence and nearly 30 mutations,” Dr Syed Pasha of the institute said. “Whereas the earlier isolate was genotype 5, the 1996 isolate is genotype 4 and is more virulent.”
“We never had such a major episode like the 1996 dengue haemorrhagic fever outbreak from any part of the country with so many cases at one particular point in time,” said Mr Datta. “Has it come from outside India? We are still not very sure.”
“We cannot even exclude that possibility,” said Dr Mahendra Yadav, director of the Indian Veterinary Research Institute.
Indian health and defence experts are not even sure about the origins of the 1994 plague episodes. “The Yersinia pestis strains that are percolating in established plague foci in India are very much less virulent and definitely different from the samples we have seen from the plague outbreak region,” said Dr Harsh Batra, joint director of the Defence Research and Development Establishment, who led the studies on outbreaks of plague. In the absence of more data and samples, he refused to attribute the 1994 plague conclusively to external biowarfare.