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The first few minutes of the recently released Dawn of the Planet of the Apes dramatizes the spread of a (fictitious) deadly “simian virus” by showing a satellite view of the planet Earth at night (see http://www.nasa.gov/mission_pages/NPP/news/earth-at-night.html ).

Continental U.S. at night, NASA satellite view

Continental U.S. at night, NASA satellite view

Lights glow brightly in all the populated areas. Then, one by one the lights go out, leaving the planet in darkness. Fortunately, not all viruses are this lethal or this fast, but with modern transportation their spread can be quite rapid. A recent example is West Nile Virus, a virus that was virtually unknown in the United States until about twenty-three years ago.
Headlines about West Nile Virus have become a predictable summer event in California. For the last six years, when the mosquitos come out, so do the headlines. “West Nile virus is making a comeback,” reads a recent CBS News headline (http://www.cbsnews.com/news/west-nile-virus-is-making-a-comeback/), while NBC reports on Santa Ana’s efforts to eradicate underground mosquito populations which are breeding out of sight in storm drains where water stands stagnant due to our drought (“Increased Risk of West Nile Virus in Santa Ana,” NBC news http://www.nbclosangeles.com/news/local/Santa-Ana-Increased-Risk-of-West-Nile-Virus-Transmission-to-Humans-266867371.html ). West Nile virus wasn’t found in the United States until 1999. Where did it come from?

The first laboratory identification of West Nile virus is well-documented. It was isolated by a Rockefeller Foundation scientist, Dr. Kenneth Smithburn, at the Yellow Fever Laboratory in Entebbe, Uganda, in 1939. The central project was to identify the boundaries of yellow fever in Uganda and prevent it from spreading by ship and by air, which was coming into increasing use at this time. Like air travel itself, viral research was a new and rapidly developing field. As he tested blood specimens for yellow fever, Smithburn found a few unknown viruses which he investigated further, publishing his findings in The American Journal of Tropical Medicine in 1940. Concerning the one he called the West Nile Virus, Smithburn wrote: “Although this virus was isolated from the blood of a human being, the circumstances of its isolation were such that nothing is known regarding the illness produced by the virus in the human subject.” 1

Announcement that five new viruses have been found. New York Times, Jan. 19, 1947.

Announcement that five new viruses have been found. New York Times, Jan. 19, 1947.

The name “West Nile” refers to the West Nile District of Uganda, where the first blood specimen that tested positive for this virus was found. This chance discovery does not imply that the virus originated or was particularly common in the area. At first, as Dr. Smithburn noted, the virus was not specifically connected with any disease in humans. In 1955 a different research team, testing for West Nile virus in conjunction with a polio survey in Egypt, found that the virus is a fairly common mosquito-transmitted disease of birds which occasionally infects humans.

In the next few decades, human outbreaks became more widespread in Europe, the Middle East, and Africa. In 1999 it made headlines when it broke out in New York, killing seven people and causing 62 cases of encephalitis. The initial identification was a mystery at first, but an unusual number of dead birds around the Bronx Zoo prompted the Centers for Disease Control to test for West Nile virus.

Article published after West Nile virus was identified in New York. New York Times, Sept. 28, 1999.

Article published after West Nile virus was identified in New York. New York Times, Sept. 28, 1999.

By 2006 it had spread to every state in the continental United States.
Unlike the fictitious virus in the movie, most people who become infected do not become ill. Unless they happened to be tested as part of a survey, they may not even know they were infected. However, a few people develop a fever and other symptoms, and even fewer develop serious neurological illness. The CDC website shows 2,469 cases in the continental U.S. in 2013, with 119 deaths. (See http://www.cdc.gov/westnile/index.html ).
Chances are West Nile virus will not put the lights out. It is, however, a vivid reminder of how a virus that primarily affects other species (in this case birds) can become a serious human disease on a global scale.

1. Kenneth C. Smithburn, T. P. Hughes, A. W. Burke, and J. H. Paul, “A Neurotropic Virus Isolated from the Blood of a Native of Uganda,” The American Journal of Tropical Medicine 20 (1940), 471.

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