About the West Nile VirusWest Nile virus belongs to a group of disease-causing viruses known as flaviviruses, which are spread by insects, usually mosquitoes. West Nile virus represents an emerging infectious disease in the United States and Canada. Most human infections are mild, causing fever, headache and body aches, often accompanied by a skin rash and swollen lymph glands. If the virus crosses the blood-brain barrier however, it can cause life-threatening encephalitis (inflammation of the brain) or meningitis(inflammation of the lining of the brain and spinal cord). Recent cases have indicated that West Nile virus can also be transmitted through blood transfusion or organ transplant. In addition, it appears that West Nile virus can also be transmitted from mother to child before birth and through breast milk.
How Do People Get Infected With West Nile VirusThe principle route of human infection with West Nile virus is through the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. The virus eventually finds its way into the mosquito's salivary glands. During subsequent blood meals, the virus may be injected into humans and animals, where it can multiply and possibly cause illness.
The first step in the transmission cycle of West Nile virus occurs when a mosquito bites an infected bird. Although the virus primarily cycles between mosquitoes and birds, infected female mosquitoes can transmit West Nile virus to incidental hosts, including humans, when taking a blood meal. Crows are commonly associated with the virus because they are highly susceptible to infection, but scientists have identified at least 75 other infected bird species.
The Spread of West Nile
West Nile virus was first isolated in Uganda in 1937. It emerged in the Western Hemisphere for the first time in the New York City area in 1999. Although health officials hoped the virus would not survive the first winter, in early spring 2000 it re-emerged in birds and mosquitoes and spread to other parts of the eastern United States and Canada.
Between 1999 and 2001, West Nile virus caused 18 deaths and sickened 131 other people. By the summer of 2002, the virus had spread west and south. As of December 20, 2002, Canadian and US health departments had reported 3,852 cases of West Nile virus in people, resulting in 241 deaths in 2002. Preliminary numbers published by the US Centers for Disease Control indicate more than 8,900 reported human cases of West Nile virus in 2003, resulting in more than 210 deaths. Of the 8900 cases reported, 68% were reported as West Nile Fever (milder disease), 30% were reported as West Nile meningitis or encephalitis (severe disease), 2% were clinically unspecified. Researchers continue to monitor and test birds and mosquitoes throughout the United States and Canada for evidence of the virus.
Top 5 states with greatest number of reported cases (Jan. 1, 2003 to Dec. 17, 2003):
|State||Reported Cases||Reported Deaths|
Please note, the dramatic difference is death rates in the 2003 figures would seem to suggest that there are wide discrepancies in the levels of monitoring and testing to confirm West Nile virus cases in humans across different states. In is gernally assumed that the number of actual cases is significantly higher than the reported numbers as many symptoms of West Nile can be mild and mimic other sicknesses, and may therefore go unreported.
No Vaccines Available
There are no drugs to treat the virus and no vaccines available to prevent infection in humans. Because West Nile virus is now established in both the United States and Canada, WHO, scientists and health experts along with public health officials, have enhanced research in an effort to contain and control the virus.
Should we be Alarmed?
West Nile Virus has the potential to cause serious disease, however, thankfully the risk of being exposed to the virus is still small and the risk of falling seriously ill is even more remote. While it would be foolish to panic, it is certainly prudent to take steps to reduce your risk of coming into contact with an infected mosquito, especially if your health is compromised by any other illness or condition such as HIV/AIDS, cancer, or other disease that might suppress your immune system. Taking practical steps to reduce the number of mosquitoes breeding in and around your property by trapping mosquitoes looking for a blood meal, and sparingly using DEET-based repellants to repel remaining mosquitoes, makes a lot of sense. Moreover, these simple precautions will also improve your outdoor experience by reducing the number of itchy bites inflicted on your family! You will also be well prepared in the event that the occurences of West Nile Virus begin to rise to more alarming levels.