West Nile virus risk factors

Who is at risk for contracting West Nile virus?

• Anyone with exposure to West Nile virus infected mosquitoes can be infected.
• People with greater exposure to West Nile virus infected mosquitoes are at greater risk contracting West Nile virus infection, e.g. outdoor occupations, outdoor recreation.
• Homeless persons have extensive outdoor exposure
• Residences lacking intact window/door screens

What habitats promote the Culex mosquito species?

• Sewer systems - cesspits, septic ditches, septic tanks.
• Container Sources - generally man-made sources that will catch and hold water, such as waste tires, buckets, and rain barrels.
• Drainage Systems - catch basins, channels, roadside ditches, and underground storm water/drainage systems.
• Open Habitats - Surface-water habitats that become stagnant and enriched to support larval development, such as swamps, marshes, bogs, rice fields, and pastures.

When do most cases of West Nile virus disease occur?

• Hot, humid environments are most amenable to mosquito growth and survival.
• Seasonal outbreaks often occur in local areas that can vary from year to year.
• Most people are infected from June through September.

Where do most cases of West Nile virus disease occur?

• West Nile virus has been detected in all lower 48 states (not in Hawaii or Alaska).
• The weather, numbers of birds that maintain the virus, numbers of mosquitoes that spread the virus, and human behavior are all factors that can influence when and where outbreaks occur.

Who is at risk for severe West Nile related morbidity or mortality?

• Age 50^+, as well as certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are at greater risk for severe disease.
• West Nile virus disease cases and deaths reported to CDC by clinical presentation, 1999-2016
  • Non-neuroinvasive disease cases - 25,512; associated deaths - 129
  • Neuroinvasive disease cases - 21,574; associated deaths - 1,888

How do I determine my local area WNV activity?

• Visit your state Dept. of Health web site and search for West Nile.
  • California https://westnile.ca.gov
  • New York https://www.health.ny.gov/diseases/west_nile_virus/docs/weekly_arboviral_surveillance_report.pdf
• Visit the CDC web site and search for West Nile https://www.cdc.gov/westnile/statsmaps/preliminarymapsdata2017/activitystate.html