New Delhi, Nov. 24: Scientists have spotted the first signals that the deadly hantavirus may be circulating in India, masquerading as other viral fever.
Through preliminary blood tests, researchers at the Christian Medical College (CMC) in Vellore have shown that 22 patients who had suffered fever without any apparent cause earlier this year were exposed to hantaviruses, which can cause respiratory distress and haemorrhage.
The researchers said the test results give the first hint that the hantavirus, which spreads to humans through the urine, droppings and saliva of infected rodents, may be making people ill in India.
“It’s possible hantavirus infections are sometimes mistakenly viewed as dengue or other fevers,” said Gopalan Sridharan, the head of clinical virology at the CMC.
Researchers at the CMC and the Kasturba Medical College (KMC) in Manipal are also investigating an outbreak of fever and severe lung symptoms, some of which turned fatal, in southern Karnataka earlier this year.
Tests on blood samples from some of these patients have revealed hantavirus antibodies, the researchers said.
The scientists, however, have cautioned that the presence of antibodies in blood is not a concrete evidence of a virus.
They have also stressed that there is no cause for alarm. Only people who inhale aerosolised particles containing infected rodent waste are likely to be at risk. “At this point in time, we do not seem to have an active outbreak anywhere in India,” a researcher said.
Hantavirus can be lethal but its symptoms and severity have changed over time. The first recognised outbreak, with fever and haemorrhage, occurred during the Korean War in 1951 with fatalities of 5 to 10 per cent.
Another outbreak in south-western US in 1993 was marked by flu-like illness followed by severe lung symptoms and a mortality of 30 to 50 per cent.
Hantaviruses do not make all infected people sick. The CMC team found hantavirus antibodies in five out of 87 healthy people.
Reporting their findings in the Indian Journal of Medical Research, Sridharan and his colleagues said there is a need for detailed studies to isolate the virus and examine rodent reservoirs in India.
There is neither a cure nor a vaccine for hantaviruses, the only treatment being medical support to keep the patient alive until the infection burns itself out.
The first and the only hint of the virus in India came 35 years ago when scientists isolated a hantavirus from the spleen of a rodent in Tamil Nadu.
Sridharan and a senior doctor at the KMC said five out of 12 blood samples collected after the Karnataka outbreak from July through October this year have tested positive for hantavirus antibodies.
“Until someone isolates the virus from the blood or body fluids of patients, we cannot say for certain that they were infected with hantavirus,” George Verghese, professor of medicine at the KMC, said.
He added that between 15 and 20 people had shown what appeared to be hantavirus pulmonary syndrome, somewhat similar to the illness in the US in 1993. The proportion of fatalities here is about 10 per cent, Verghese said.
The researchers said blood samples from the Karnataka outbreak have been sent to the National Institute of Virology in Pune to authenticate the findings. A senior scientist at the institute declined to comment on the investigations.