Every year warm weather and outdoor activities result in those itchy red bumps-mosquito bites. Up until this summer, mosquitoes were nothing more than an aggravation that existed during the summer months. Now, the appearance of red spots leads to one worrisome thought-the West Nile virus.

The West Nile virus, a flavivirus transmitted by either mosquitos or ticks that causes hemorrhagic fever, originated in Africa, Asia, and the Middle East. It was first detected in humans in the West Nile District of Uganda in 1937 and received its name from the name of the place it is thought to have originated. It was not until 1999, however, that the virus made its way to North America [1]. It is unknown how the North American strain of the West Nile virus came to be, but genetically it is very similar to the strains found in the Middle East.

Mosquitoes are the vectors by which the West Nile virus is transmitted. Mosquitos hold the virus in their salivary glands, so that every time the feed, they infect their host. People, birds, and other animals can be infected when bitten by an infected mosquito. Typically the virus produces mild symptoms or none at all. On rare occasions, however, the infection can become serious and possibly fatal.

The mild version of the disease is called "West Nile fever." Nearly twenty percent of the people infected develop this mild infection [2]. The symptoms are flu-like and typically last three to six days. The incubation period, however, is around three to fourteen days long [2]. West Nile fever is characterized as a feverish illness that comes about suddenly. The symptoms may include malaise, nausea, vomiting, headache, rash, eye pain, anorexia, and lymphadenopathy [2]. There seems to be no lasting effects on a person's health after the infection.

On the other hand, the West Nile virus results in a severe neurological infection approximately one in every 150 infections [2]. The severe versions of the disease include West Nile encephalitis, West Nile meningitis, and West Nile meningoencephalitis. Encephalitis is more common than meningitis. These severe illnesses may have duration of a couple of weeks.

The symptoms that may appear with the severe form of infection include fever, weakness, gastrointestinal symptoms, changes in mental status, muscle weakness, seizures, cranial nerve abnormalities, and bodily rash [2]. There is also a possibility that any neurological damage will be permanent. The severe infections due to West Nile virus have occurred in patients of all ages, however the risk for developing severe neurological disease is greater in elders.

The treatment for West Nile disease varies with the severity of the illness. Treatment is more rigorous for the severe cases, and can include hospitalization, the use of intravenous fluids, and respiratory support. The vaccine for the West Nile virus has yet to be discovered.

The spread of West Nile virus in the United States was slow after its appearance in 1999. The three-year period preceding its first appearance, the virus had spread to twenty-eight states in the East Coast and Midwest [3]. In 2002, however, the virus began to spread across the nation at such an alarming rate that it reached epidemic status. As of October 2002, only seven states had not detected West Nile virus. The virus was first detected in the state of Illinois in September 2001, when laboratory results revealed that two crows had died of the virus. Since then, with 640 viral-positive reports and thirty-six fatalities, Illinois has been shown to have the most human cases and deaths in the United States [4].

The most prevalent means of infection is via infected mosquito bites. There have been cases that show that West Nile disease, however, can be transmitted through transplant organs and blood transfusions. There is also currently an investigation into whether or not an infant can contract the West Nile virus from its mother's breast milk.

Precautions can be taken to minimize the chances of being infected with West Nile virus. Using insect repellent that contains DEET, wearing long-sleeved shirts and long pants, and avoiding the outdoors during dawn and dusk will diminish the likely of being bitten by mosquitoes, thus decreasing the chances of contracting the virus.

One question that remains is whether the West Nile virus will make a return during the summer of 2003. It is believed that the cold of the winter will kill all the current infected mosquitoes, however, the concern is that a large percentage of the dormant mosquito eggs that will hatch in the spring will be infected. Thus, current trends in the spread of West Nile virus show that an even greater epidemic will most likely occur next year. There is little we can do to prevent the spread of the West Nile virus. We can only work to prevent infection, while a vaccine to the West Nile virus is in the works.

Peggy is a third-year student majoring in Biology. She plans to attend medical school in Fall 2003.