Nipah virus, a newly emerging deadly paramyxovirus isolated during a large outbreak of viral encephalitis in Malaysia, has many of the physical attributes to serve as a potential agent of bioterrorism. The outbreak caused widespread panic and fear because of its high mortality and the inability to control the disease initially. There were considerable social disruptions and tremendous economic loss to an important pig-rearing industry. This highly virulent virus, believed to be introduced into pig farms by fruit bats, spread easily among pigs and was transmitted to humans who came into close contact with infected animals. From pigs, the virus was also transmitted to other animals such as dogs, cats, and horses. The Nipah virus has the potential to be considered an agent of bioterrorism.
An outbreak of encephalitis affecting 265 patients (105 fatally) occurred during 1998-1999 in Malaysia and was linked to a new paramyxovirus, Nipah, that infected pigs, humans, dogs, and cats. Most patients were pig farmers. Clinically undetected Nipah infection was noted in 10 (6%) of 166 community-farm controls (persons from farms without reported encephalitis patients) and 20 (11%) of 178 case-farm controls (persons from farms with encephalitis patients). Case patients (persons with Nipah infection) were more likely than community-farm controls to report increased numbers of sick/dying pigs on the farm (59% vs. 24%, P=.001) and were more likely than case-farm controls to perform activities requiring direct contact with pigs (86% vs. 50%, P=.005). Only 8% of case patients reported no contact with pigs. The outbreak stopped after pigs in the affected areas were slaughtered and buried. Direct, close contact with pigs was the primary source of human Nipah infection, but other sources, such as infected dogs and cats, cannot be excluded.