Scientifically Speaking | Mysterious deadly viruses spread by insects are on the rise
A proactive approach, including insecticidal spraying, education on preventive practices, and surveillance is necessary to quickly respond to these cases
Few people want to talk about viruses, especially five years after a deadly coronavirus brought the world to its knees. Yet, as mpox continues to rage in Central Africa and beyond, and new threats like H5N1 influenza find hosts in cattle and people across the United States, we ignore viruses at our peril. To make matters worse, viruses spread by mosquitoes and other insects are ravaging the world.
Though no one knows all the reasons why there’s been a surge in viral diseases spread by insects, climate change is partly to blame. For example, climate change is making mosquito seasons longer and the geographic range of mosquitoes much more varied.
Dengue fever is reaching unprecedented levels with over 11 million cases worldwide this year, almost double last year’s tally. In eastern India, many of my acquaintances were infected with dengue for the first time in their lives.
Meanwhile, in the US, Eastern equine encephalitis, a rare but lethal virus, is making headlines with cases reported in several states. With a mortality rate of about 30%, this virus is particularly alarming as mosquitoes remain active longer each year due to rising temperatures.
Have you heard of Chandipura or Oropouche before? These insect-spread viruses are now in the news in the same way that Zika and Chikungunya were years ago when they became global health crises. This year, alarming spikes in Chandipura and Oropouche are taking different parts of the world by storm.
Chandipura virus, found in India and most harmful to children, is experiencing its biggest outbreak in twenty years. Oropouche virus, usually seen in South America’s Amazon basin, is now spreading across wider areas of South America and has even shown up in unexpected places like Cuba. Both viruses are deadly.
Let's start with Chandipura. The virus is endemic across India's western, central, and southern regions. Chandipura virus causes acute encephalitis syndrome, which can quickly progress from fever and malaise to severe neurological symptoms like seizures and coma, often within days. What’s most concerning is that it has a fatality rate as high as 56-75% in recent outbreaks.
The latest outbreak has been particularly severe, with 245 reported acute encephalitis syndrome cases and 82 deaths, primarily in Gujarat and Rajasthan. Outbreaks, which typically occur every four to five years, often coincide with the monsoon season, providing ideal conditions for the virus's vectors (not just mosquitoes, but also sandflies and ticks).
The rapid progression of symptoms and high death rate make Chandipura worrying. In response, the Indian ministry of health and family welfare has ramped up efforts to control and contain its spread. These efforts include intensified vector control measures like insecticidal spraying, public education on preventive practices, and enhanced surveillance to quickly detect and respond to cases. This proactive approach is necessary because there’s no treatment or vaccine for the virus.
The WHO has also called for ongoing research and monitoring to keep track of the virus's potential to spread to new regions. Given the changing climate and increased human mobility, there's a real possibility that Chandipura could spread to new areas and insect hosts.
Let's shift focus to the Oropouche virus, first identified in 1955 in Oropouche, Trinidad and Tobago. Although it caused outbreaks in the Amazon region in the past, it never drew much global attention. This lack of focus is partly because it didn’t spread widely. The hosts in the forest included animals like pale-throated sloths and non-human primates. Insect vectors include midges and possibly Culex mosquitoes.
This year, the virus has significantly expanded, affecting over 8,000 people across Bolivia, Brazil, Colombia, and Peru, and even reaching Cuba for the first time. Oropouche virus is spreading to urban areas, suggesting it might start a cycle where humans amplify its spread, much like Zika.
Oropouche fever symptoms are typically mild, including headaches, fever, muscle, and joint pains. These symptoms are similar to those of dengue or Zika. But alarmingly, it has caused its first recorded deaths, involving two young women in Brazil. Like Chandipura, there are no treatments or vaccines for Oropouche either.
There’s growing concern that Oropouche could spread internationally as travel picks up post-pandemic. Cases among US travellers returning from affected regions have put health authorities on alert in that country. But more needs to be done now. We need research on how the virus spreads and better preparedness to prevent Oropouche from becoming the next Zika.
Right now, Chandipura and Oropouche might not be on our radar, but that needs to change. Recall the example of Chikungunya, a viral disease that was virtually unknown in India during my grandparents' time. First identified in Tanzania in 1952, Chikungunya has spread worldwide over the decades. Although the first outbreak of Chikungunya fever was reported in India in 1963, it was dormant for 32 years. The virus reemerged in 2005 and led to a major outbreak in India in 2006, swiftly spread by the Aedes mosquitoes (which are also carriers of dengue and Zika viruses).
Anirban Mahapatra is a scientist and author, most recently of the popular science book, When The Drugs Don’t Work: The Hidden Pandemic That Could End Medicine. The views expressed are personal.
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