The Institute of Advanced Virology, Thonnakkal, Thiruvananthapuram, has acquired PCR testing equipment to confirm the diagnosis of hantavirus infections.
As the emergence of a rare strain of hantavirus with the potential for human-to-human transmission raises global health concerns, virologists and doctors in Kerala are considering a crucial public health question: What proportion of acute febrile illnesses with renal syndrome and thrombocytopenia (low platelet count) reported in the state, currently attributed to suspected leptospirosis, may actually be caused by hantavirus?
The Health Department is very much aware of the fact that hantavirus (scientific name is Orthohantavirus) could be an emerging pathogen in the state, as hantavirus seropositivity (presence of hantavirus antibodies in blood samples, indicative of infection) has already been reported in Kerala in numerous research studies and as early as 2008. The state has also reported one probable renal syndrome-induced hantavirus fever. mimicked leptospirosis in 2014, but there was no confirmatory diagnosis at the time.
Kerala experiences a huge burden of leptospirosis cases every year, with farming, sanitation work and monsoon floods driving the spillover of the pathogen from animals to humans. Rodent-borne hantaviruses also circulate in the same agro-ecological zone, meaning human exposure to these viruses is likely.
Two main diseases
Hantavirus is primarily known to cause two major human diseases, Hantavirus Pulmonary Syndrome and HFRS, the latter being more common in India.
The clinical signs of both leptospirosis and hantavirus-induced HFRS—high fever with myalgia, decreased platelet count, acute kidney injury, and hemorrhagic manifestations—are so similar that they are often indistinguishable without targeted serologic testing.
“Our doctors are very aware that one of the differential diagnoses of leptospirosis is infection with hantavirus. The theory is that the large number of ‘leptospirosis’-like illnesses we see, in which patients deteriorate and die within four to five days, may be caused by hantavirus or co-infection between leptospirosis and hantavirus. These cases often remain documented as a ‘probable lack of time,'” says R. Aravind, head of the infectious disease department of Diseases, Government Medical College, Thiruvananthapuram.
Mortality rate up to 15%
HFRS caused by hantaviruses is a serious disease with a reported mortality of up to 15% in Southeast Asia, but no human-to-human transmission has been reported.
“Hantavirus may be an emerging pathogen for the state, but there is no immediate threat to public health. Unlike before, we now have diagnostic facilities at the Institute of Advanced Virology (IAV) and HFRS cases that are negative for leptospirosis are routinely tested for hantavirus,” says Dr. Aravind.
In one of the most recent studies published in December 2025 by Chandy et al, serum samples from 216 febrile patients presented at Lisie Hospital, Kochi were tested for anti-orthohantavirus IgM and IgG antibodies. Overall, 16.2% of samples were positive for anti-orthohantavirus IgM and 11.57% for IgG antibodies, with both IgM and IgG detected in 4.63% of samples, indicating possible exposure to the virus.
Now better access to tests
Hitherto, access to both serological tests such as IgM Elisa as well as molecular diagnostic tests such as hantavirus PCR has been limited in Kerala and across the country. (Serological tests have their limitations, as detectable levels of antibodies may not show up in the tests in the acute phase of the disease. There is also a risk of cross-reaction of hantavirus with other viruses, leading to false negatives).
IAV has now filled this diagnostic void with the acquisition of a PCR testing device to confirm the diagnosis of hantavirus infections.
“We have never done active surveillance for hantavirus despite serological evidence of virus circulation. We now routinely PCR test clinical samples from Thiruvananthapuram MCH for hantavirus, but there have been no positive cases so far,” says E. Sreekumar, Director, IAV. IAV also initiated some basic biological studies of the virus.
Published – 09 May 2026 21:07 IST
