West Nile Virus

About the Virus

Clinical Signs






Zoonotic Risk

Veterinarian's Role

Helpful Links



Zoonotic Risk

Humans get infected from West Nile Virus through mosquito bites. All age groups are susceptible to the viral infection, but the elderly, immune compromised people, pregnant women, and people with certain genetic mutations are more likely to develop mild to severe forms of disease. The incubation period in humans is usually 2 to 15 days (incubation is the time from infection to onset of disease symptoms).

Approximately 20% of the people who are infected with the virus will develop mild clinical illness which is called “West Nile Fever”.

Common signs and symptoms of West Nile Fever include:

•    Fever
•    Headache
•    Body aches
•    Loss of appetite
•    Nausea, vomiting and diarrhea
•    Skin rash
•    Swollen lymph glands

Less than 1% of infected people may develop more serious neurological diseases such as encephalitis, meningitis, meningoencephalitis, and paralysis.

Signs and symptoms of these diseases include:
  • Stiff neck
  • High fever
  • Severe headache
  • Disorientation
  • Coma
  • Muscle jerking or tremors
  • Convulsions
  • Lack of coordination

Symptoms of West Nile Fever usually last a few days; however, the severe form of the disease may last several weeks to months with some permanent CNS effects.

So far there is no evidence of person-to-person, animal-to-animal, or animal-to-person transmission of West Nile Virus. In rare cases, it is possible for humans to get infected with the virus through different routes other than mosquito bites such as blood transfusion, mother to fetus, breast feeding, and organ transplantation.

Currently there is no specific treatment available for West Nile Virus infection or vaccine to prevent it. However, most people recover from it without any treatment. In case of severe illness hospitalization, use of IV fluids and nutrition, respiratory support, prevention of secondary infections and good nursing care will be necessary. It is important to seek out medical care as soon as possible for people who have symptoms of severe illness.



University of Florida: What Is West Nile Virus and How Does It Affect Humans and Horses?

Extension Disaster Education Network: West Nile Virus.

Center for Disease Control: Symptoms of West Nile Virus.

Image References

Communicable Disease Control and Prevention San Francisco Department of Public Health

Maryland Department of Health and Mental Hygiene: http://edcp.org/html/wn.html