History of the West Nile Virus

Through phylogenetic lineage studies, it was known that the West Nile Virus (WNV) is already a disease that existed a thousand years ago.

It had two different lineages: the first, as a epidemic disease, alongside these are the other diseases associated with it, and the second, as a zoonose, or organisms that are said to be the reason for its transmission yet are not carriers of any infectious disease. Both developed in Africa.

It was way back in 1937 in West Nile District in Uganda that the virus was discovered in an attempt to make further researches on the yellow fever virus by scientists. However, it was only in the 1940s in Egypt and in the 1950s in India that it was later known.

It was entirely recognized when there was an outbreak of meningoencephalitis in Israel in 1957. In succeeding years, it was found in animals, especially in horses, in France then it spread in the other countries, primarily some parts in Europe, Australia and certain countries in Asia.

Cases of encephalitis on humans and certain animals like dogs, cats and horses as the virus spread across the western hemisphere in 1999. Then it gradually came to the United States as there were outbreaks in New York City, New Jersey and Connecticut. Afterwards, the infected countries included the Caribbean, Mexico, Canada and certain regions of Central America.

As it was taken into account that a high number of dead birds indicated the arrival of the virus, it was noted that too many birds, as it was for humans and horses, that have come in contact with the virus.

In areas with high population of birds, especially of those that fall under the corvidae family (crows, ravens, jackdaws, for example), showed the presence of strains in both US and Israel.