As eastern India grapples with the avian influenza virus H5N1, virologists have revealed another shocker: that the life threatening hantavirus has also surfaced in the country.
In the first report of evidence of hantavirus in India, a multi-institutional study1 has confirmed 28 cases of infection among patients with chronic renal disease, warehouse workers and members of the Irula tribe engaged in rodent trapping in the Vellore district of Tamil Nadu.
Irulas are traditional snake and rat catchers. Their population in Tamil Nadu is estimated to be at least 25,000. Hantavirus is carried by rodents, though the animals themselves do not get sick from the virus. It is then excreted through body fluids like saliva, faeces and urine. As the fluids dry or evaporate, the virus spreads into the air and can be inhaled by humans. Once in the lungs the virus infects the endothelial cells and spreads through the lymphatic system to lymph nodes, then to other body organs. However, hantavirus infection is not contagious — it does not spread from human to human. Working or living in a rodent infested setting or breathing dust after cleaning rodent droppings or nests increases the chance of exposure to the virus.
The research team looked at specific groups of people who had serological evidence of exposure to hantavirus — a complex group of viruses that trigger the respiratory disorder Hantavirus Pulmonary Syndrome (HPS). This is characterized by respiratory distress and shortage of breath. Symptoms also include fever, chills, nausea, vomiting, abdominal pain and muscular pain.
There had been no documented case of hantavirus disease from India prior to this, although serological evidence existed2,3. The team investigated the presence of hantavirus-specific IgG antibodies in 661 people belonging to the different risk groups. In all, 38 seropositive samples were found using a combination of a commercial ELISA test followed by an indirect immunofluorescence assay. Western blot test confirmed the presence of anti-hantavirus IgG in 28 of these samples.
"The study confirms the presence of hantaviruses in India and warrants increasing awareness of the problems of emerging pathogens and the threats they may pose to the public health system," the team said. Though they have not been able to identify all the types of hantaviruses present in the population, they have evidence of the Seoul, Thailand and Hantaan types being present in the samples.
Hantaviruses are members of the virus family Bunyaviridae and are enveloped, single-stranded RNA viruses. Several species have been identified worldwide including China, the Korean peninsula, Russia (Hantaan, Puumala and Seoul viruses) and northern and western Europe (Puumala and Dobrava viruses).
The team contends that since no previous published data on hantavirus infections in India was available and not much was known about laboratory diagnosis or clinical cases, doctors are unaware of the cause or origin of hantavirus. "This suggests that there could be circulation of the hantaviruses in the Indian population," they wrote in an earlier paper in 2005.
Further studies were needed to identify hantaviruses in clinical samples by molecular techniques to be sure of the clinical picture of hantaviral infections in India. These techniques will also help to identify the rodent reservoirs and to focus on the importance of potentially unknown hantaviruses in India.
"The presence of hantavirus in India has been speculated for several decades," writes Deepak Gadkari in the September 2005 issue of Indian Journal of Medical Research4. The former director of Pune-based National Institute of Virology says, "This is the first time that evidence of its presence has been documented. It is a classic case of 'you look for more and you will find more'."
"The stage has been set for Indian scientists and public health workers to take off from here," he points out.
The researchers of this work are from:
Department of Clinical Virology, Christian Medical College, Dr. Ida Scudder Road, Vellore, India; Institute for Animal Experimentation, Graduate School of Medicine, Hokkaido University, Sapporo, Japan; Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute for Novel and Emerging Infectious Diseases, Boddenblick 5a, D-17493 Greifswald – Insel Riems, Germany; Department of Microbiology, Post Graduate Institute for Basic Medical Sciences, Madras University, Chennai, India; Department of Nephrology, Christian Medical College, Vellore; Department of Community Health, Christian Medical College, Vellore; Department of Clinical Pathology & Blood Bank, Christian Medical College, Vellore