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A Plague of Israel Reaches the American East Coast – The West Nile Virus. Part 3

by Daniel on September 13th, 2011

The Virus

The West Nile Virus belongs to a group of viruses called flaviviruses, originally termed type B arboviruses. Arboviruses are those that flourish in both vertebrates (such as humans, horses, and birds) and arthropods (such as mosquitoes and ticks). Like Ebola, West Nile Virus is an RNA virus. Among others things, this means the virus has a high incidence of mutations when replicating itself, which often results in the emergence of new strains. Other flaviviruses cause yellow fever, varieties of viral encephalitis, and dengue fever, all of which are mosquito-borne illnesses. Both yellow fever and dengue occur almost exclusively in tropical parts of Africa, and have not been seen in North or South America since the 1940’s. The West Nile Virus in particular has, until last year, only been found in Africa, Mediterranean Europe, and West Asia. It was first discovered in Uganda in 1937. Subsequent locations of human outbreaks included Egypt in the 1950s and Israel in 1957. Equine infections manifested in Egypt and France in the 1960s.

The biggest epidemiological mystery surrounding WNV’s outbreak in the eastern United States is how it got here. The current theory is that the most likely “reservoir” for the virus in North America is the common sparrow, which can tolerate the infection. A reservoir refers to a host species where the virus can live between outbreaks, without causing symptoms or illness in the host organism. The million-dollar question for epidemiologists right now is how this reservoir became established – how did it become infected in the first place?


As mentioned, the incubation period for the virus in mosquitoes is ten to fourteen days. This means the mosquito has had a blood meal from an infected organism, such as a bird. After the 10-14 day period, the virus is present in the mosquito’s salivary glands, where it is transmitted to any organism the mosquito feeds on.

Populations most at risk for infection are seniors and other populations with compromised immune systems. However, anyone who spends time in wooded areas and any humid climates should take precautions.

How does the infection occur?

When a mosquito takes its blood meal, it first injects its saliva into the organism it feeds from. The saliva contains many chemicals, some of which thin the blood so that the mosquito can take it in easier. The saliva in an infected mosquito also carries the virus. Once injected by the mosquito into the victim’s blood, the virus enters the blood stream and multiples. It then “crosses the blood-brain barrier to reach the brain. The virus interferes with normal central nervous system functioning and causes inflammation of brain tissue.”

Symptoms of Infection

Mild infections are similar to flu, including fever, headache, and body aches, often with skin rash and swollen lymph glands.

In more severe cases (which can lead to encephalitis, brain damage and even death), symptoms include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions, and paralysis.

The CDC lists the mortality rate from West Nile Virus as being about 3 to 15 percent, with senior victims being the most likely to die from infection.


Anyone who hikes in the woods or bushes should use standard protocol for dealing with pests, such as long-sleeved shirts and long pants, insect repellent with 10-30% DEET on both one’s exposed skin and one’s clothing, and possibly even bug hats. It is recommended that people stay indoors at dawn and dusk because those are the times when mosquitoes are most active.

It is recommended that you remove any sources of standing water from around your property, as these are potential breeding grounds for mosquitoes.

Mosquitoes become inactive in temperatures below 55 degrees Fahrenheit. With weather in the Eastern US and Canada cooling off, this year’s outbreak is expected to be quelled soon. Officials decline to state whether West Nile Virus is becoming an established epidemic in the US like in Israel, saying that there is not enough evidence to draw such a conclusion at this time. However, most experts are willing to speculate that the virus will return next summer. They site the fact that the known carrier species are types of “house” mosquitoes, which are capable of ‘hibernating’ through the winter in the cracks and crevices of domiciles and other warm buildings.

So far, the West Nile Virus has not shown any movement inland, seemingly moving along the coast. However, it remains to be seen how the face of this outbreak will change if, or when, the virus returns next summer.

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