Light Pollution Raises Risk of West Nile Virus, Study Shares

In a news release from California Polytechnic State University (“Cal Poly”), the University shares how a joint study between itself and the University of South Florida (“USF”) has garnered new information regarding the spread of West Nile virus. Over the last 17 years in California, this virus resulted in over 7,200 infections and 320 deaths. Now, the recent study highlights how light pollution contributes to the spread of this sometimes dangerous mosquito-borne virus. Check out the full findings published in Proceedings of the Royal Society B.

Light Pollution

According to the International Dark-Sky Association (IDA), light pollution is:

The inappropriate or excessive use of artificial light [which] can have serious environmental consequences for humans, wildlife, and our climate. Components of light pollution include:

  • Glare – excessive brightness that causes visual discomfort
  • Skyglow – brightening of the night sky over inhabited areas
  • Light trespass – light falling where it is not intended or needed
  • Clutter – bright, confusing and excessive groupings of light sources

Sources of light pollution include street lights, illuminated sports or concert venues, advertisements, office buildings, interior and anterior lighting, and more. In addition to negatively affecting energy consumption, light pollution can also be detrimental to the environment. For example, outside of Zika virus spread, light pollution could interrupt the migratory pattern of birds, change animal breeding or hunting patterns, or draw baby turtles away from the ocean.

The Research

Prior research has attributed the spread of West Nile virus to the increase in population, population density, and urban areas where mosquitos can breed in drainage systems and other “hot spots.” However, this research team is one of the first to associate West Nile virus with light pollution.

To do this, the researchers examined 6,468 antibody samples sourced from chickens from 105 coops throughout California. The sources were collected between June-December over a 4-year period. Researchers explored the relationship between infection and three levels of light: unpolluted areas, low light pollution, and high light pollution. They determined that the chickens from low light pollution areas experienced the most West Nile virus infections.

Ultimately, the research suggests that infected birds and mosquitos are often attracted to artificial light. Thus, areas with lower light pollution serve as a mid-point of attraction. As mosquitos become more attracted to the lights, so do the infected birds, raising the risk of West Nile virus in a specific location. Moving forward, to mitigate the spread of West Nile virus, states and counties could consider reducing levels of light pollution.

West Nile Virus

Most commonly spread by mosquitos, West Nile virus is an infectious disease which may cause adverse reactions. After feeding on infected birds, mosquitos transmit the virus to humans. However, blood transfusions, organ transplants, laboratory exposure, and pregnancy can also transmit the virus. West Nile virus is considered the most common mosquito-borne illness in America. In many cases (around 80%), those infected have either no symptoms or mild symptoms. These mild symptoms include:

  • Nausea and vomiting
  • Joint and muscle aches
  • Fever
  • Headache
  • General malaise
  • Diarrhea
  • Rash

In mild cases, patients usually recover without issues. But in a small number of cases (1 in every 150), the virus may spread to the brain, causing severe and dangerous side effects. Typically, those most at risk are those who are immunocompromised or older than 60. Symptoms, which may be fatal, include:

  • Headache
  • Vision loss
  • High fever
  • Muscle pain, weakness, and/or numbness
  • Tremors and/or convulsions
  • Neck stiffness
  • Confusion and disorientation
  • Encephalitis (brain inflammation)
  • Meningitis
  • Coma
  • Paralysis

Symptoms usually appear within 3-14 days of infection. In severe cases, patients may require hospitalization, respiratory support, and IV fluids.

Learn more about West Nile virus.

Jessica Lynn

Jessica Lynn

Jessica Lynn has an educational background in writing and marketing. She firmly believes in the power of writing in amplifying voices, and looks forward to doing so for the rare disease community.

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