India Sees Largest Chandipura Virus Outbreak In 20 Years: All We Know

Since early June, India has been experiencing its worst outbreak of the Chandipura virus in more than 20 years. At least 38 people have died from the infection, most of them children and teenagers.

This rod-shaped virus belongs to the same family as the rabies virus. It is mainly transmitted by sandflies, small midges whose females feed on blood. However, mosquitoes and ticks can also spread it.

Initial symptoms are similar to those of the flu, but they can quickly progress (within 24 to 48 hours) to encephalitis, which is inflammation and edema (swelling) affecting the brain, which can lead to coma or even death. Children under 15 years of age are most vulnerable to illness.

The exact way the virus enters the central nervous system (brain and spinal cord) and causes encephalitis is still poorly understood. The virus is thought to be transmitted through the saliva of the infected insect, when it bites to take its blood meal. The virus then travels into the bloodstream, infecting immune cells called monocytes (a type of white blood cell). There, it multiplies, hidden from the immune system. It is then transported to the central nervous system, where it enters the brain, disrupting the blood-brain barrier, the shield that is supposed to protect this essential organ (as well as the spinal cord).

Six hours after infection begins, the Chandipura virus secretes a protein called phosphoprotein into brain cells, which may explain why death occurs so quickly .

Unfortunately, at present there is no antiviral treatment or vaccine.

A relatively recent threat, accentuated by climate change

The Chandipura virus is named after a village in the state of Maharashtra, India. It was first identified there in 1965. However, the first major outbreak did not occur until 2003 in southern India (the state of Andhra Pradesh). That year, 329 children tested positive for the virus, and 183 died from the infection. In 2005, during an outbreak in the state of Gujarat (northwest India), 26 cases were identified, with a high mortality rate (78%).

The most recent outbreak, also in Gujarat, affected 100 people. It had a particularly severe impact on children under 15 who had been infected. At the time, the rapid spread of the virus and the severity of symptoms had raised concerns among public health authorities.

Since the virus was discovered in 1965, most cases have occurred in the Indian subcontinent. However, this may be changing: the geographical distribution of the virus is expanding beyond India. It was identified in sandflies in West Africa in 1991 and 1992, and in hedgehogs in Senegal (between 1990 and 1996). Antibodies to Chandipura virus were also detected in wild monkeys in Sri Lanka in 1993, suggesting that they too had been in contact with the virus.

The emergence of the Chandipura virus is likely linked to climate change, with its spread being facilitated by rising temperatures.

Several other viral diseases spread by insects (arboviruses, for "ARthropod-BOrne VIRUSes" in English) have also progressed in recent years due to climate change. This is particularly the case for several diseases caused by viruses transmitted by mosquitoes, such as the Zika virus, the dengue virus and the Nipah virus.

This article was first published by Manal Mohammed, Senior Lecturer, Medical Microbiology, University of Westminster in The Conversation.