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The Cycle of West Nile Virus

The Cycle of West Nile Virus. William R. Barnett MEDT 450 December 2, 2003. Introduction. In 1937, the virus was first isolated in Uganda. Most prevalent in Africa, Eastern Europe, the Middle East, and West Asia. In 1999, cases of West Nile virus began to exist in North America.

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The Cycle of West Nile Virus

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  1. The Cycle of West Nile Virus William R. Barnett MEDT 450 December 2, 2003

  2. Introduction • In 1937, the virus was first isolated in Uganda. • Most prevalent in Africa, Eastern Europe, the Middle East, and West Asia. • In 1999, cases of West Nile virus began to exist in North America. Source: National Institute of Allergy and Infectious Diseases (NIAID)

  3. Introduction con’t • According to the CDC, West Nile virus activity for 2002: • Michigan: 614 cases, 51 deaths • Ohio: 441 cases, 31 deaths • Indiana: 293 cases, 11 deaths • Pennsylvania: 62 cases, 7 deaths • Kentucky: 75 cases, 5 deaths

  4. Introduction con’t • According to the CDC, West Nile virus activity for 2003: • Michigan: 15 cases, 1 death • Ohio: 107 cases, 4 deaths • Indiana: 41 cases, 4 deaths • Pennsylvania: 232 cases, 7 deaths • Kentucky: 14 cases, 1 death

  5. Cycle of Infectious Disease • Pathogen • Reservoir • Method of Transmission • Susceptible Host

  6. Pathogen • An infectious disease caused by a virus family known as flaviviridae. • West Nile virus is classified as an “arbovirus”: arthropod-borne virus • Related strains of flaviridae may cause encephalitis. Source: CDC Picture: NIAID

  7. Reservoir • The pathogen develops in a non-human host. • Most often, crows, ravens, and blue jays carry West Nile virus. • Humans and non-bird hosts are not considered reservoirs. Source: CDC Picture: www.west-nile-prevention.com

  8. Method of Transmission • West Nile virus is transmitted through mosquitoes who feed on infected birds. • The infected mosquito can spread the virus to other animals and humans. • The pathogen is not transmitted through contact or the air. Source: CDC Picture: www.west-nile-prevention.com

  9. Susceptible Host • Birds can develop symptoms in 1 to 4 days and then acquire immunity to the virus. • Many mosquitoes must feed on a bird to effectively spread West Nile virus to another host. • Humans and other animals usually do not develop symptoms and will eventually become immune to further infections. Source: CDC

  10. Cycle of West Nile Virus

  11. Clinical Features in Animals • Birds • Become infected and usually recover. • Death from encephalitis. • Horses • Become infected and usually recover • Death from encephalitis. • Dogs and Cats • Usually show no symptoms. Source: CDC

  12. Clinical Features in Humans • Mild Infection • 1 in 5 • 3-14 day incubation period • 3-6 day range of symptoms: • Malaise • Nausea • Vomiting • Headache • Rash • Myalgia Source: CDC

  13. Clinical Features con’t • Severe Infection • 1 in 150 • Encephalitis • Meningitis • Severe neurological disease Source: CDC

  14. Diagnosis • Suspected cases of West Nile virus are based on symptoms and patient history. • Confirmed cases are diagnosed through measurement of antibodies in the blood or cerebrospinal fluid (CSF). • In some cases, a plaque reduction neutralization test (PRNT) will be performed. Source: CDC

  15. Treatment • There is not a specific treatment for West Nile virus. • In severe cases: • hospitalization • IV fluids • airway management • ventilation • prevention of secondary infections Source: CDC

  16. Preventative Measures • West Nile virus is preventable. • Some ways to stop the cycle of West Nile virus: • Inhibit mosquito breeding. • Avoid peak mosquito times. • Dress appropriately. • Use DEET or other “mosquito repellants”. • Spread the word to friends, family, and neighbors.

  17. Conclusion • West Nile virus has been active in the United States since 1999. • The pathogen is a flavivirus. • The reservoir for the virus is birds. • The method of transmission is from bird to mosquito. • West Nile virus can cause neurological disease. • Diagnosis of West Nile virus is through symptoms, history, and tests. • There is not a specific treatment for the disease. • The virus is preventable.

  18. Questions ?

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