By David N. Leff
Since it made landfall in New York City two summers ago, the West Nile flavivirus has killed 10 Americans. This is more than twice the four laid low by the current anthrax wave. No one suggests or suspects that West Nile is the work of Osama bin Laden or al Qaeda. Yet, its modus operandi ¿ often culminating in fatal encephalitis ¿ smacks of terrorism.
One who knows the ways of the West Nile virus better than most people is entomologist John Anderson, director of the Connecticut Agricultural Experiment Station in New Haven. ¿I happen to believe,¿ he predicted, ¿that this virus will move not only from southern New England into the Southeastern states ¿ that, it¿s already done ¿ but also will move down into Central America and South America, so that this West Nile virus in time will be distributed to a goodly portion of the Western Hemisphere.¿
As evidence for this grim prospect, Anderson recalls West Nile¿s present distribution in the Eastern Hemisphere: ¿West Nile virus occurs naturally in a good proportion of Africa,¿ he recounted. ¿In fact, it¿s found all the way from South Africa¿s southern tip into the continent¿s northernmost country, Egypt and historically Uganda ¿ which accounts for the West Nile name ¿ then moved on into southern and central Europe. It¿s a virus that occurs in both tropical and subtropical zones as well as in temperate areas. So it is primarily associated with tropical and subtropical regions of Africa.
¿West Nile made its appearance in the temperate northeastern U.S. ¿ namely, New York, New Jersey and Connecticut ¿ in the late summer and early fall of 1999,¿ Anderson recounted. ¿Here we are now completing the year 2001. Clearly, the virus has survived in our temperate areas, but it has quickly moved into Florida, Louisiana and other Southern states in a matter of the last couple of years.
¿More than likely, this movement of the virus has been brought about by its natural distribution to North American birds that are cycling southward to avoid the harsh winter weather. Some of those bird migrate on down into South America and Central America. So it¿s just a prediction on my part that this virus is going to continue moving.¿
Anderson is senior author of a paper in the current Proceedings of the National Academy of Sciences (PNAS), dated Nov. 6, 2001. Its title: ¿A phylogenetic approach to following West Nile virus in Connecticut.¿
Census Of Birds, Bugs ¿ Plus One Skunk
¿In the year 2001 we have isolated West Nile virus in 14 species in Connecticut,¿ Anderson told BioWorld Today. ¿In the PNAS paper, we reported the virus to be prevalent here in southern New England in nine species of birds, five of mosquitoes, and one striped skunk. Also, we found a number of changes in the viral nucleotide sequence in both invertebrate and vertebrate animals. These changes,¿ he observed, ¿are presumably recent, because this virus is known to have been present in North America only since 1999. That was the year that West Nile was isolated and identified. It¿s possible that it had been here prior to 1999, but we have no evidence for that at this time.
¿We don¿t know the effects of these genetic viral changes,¿ Anderson said. ¿What we did was to record a number of alterations, and found one that¿s known as a silent mutation. It didn¿t modify any amino acids, but it was prevalent around the city of Stamford, Conn.¿ not too far from New York ¿ where we mapped a dense cluster of the transformed viral isolates. They were indistinguishable from the strain that we used as the West Nile standard ¿ isolated from the Chilean flamingo that died in the Bronx Zoo in September of 1999. (See BioWorld Today, Dec. 16, 1999, p. 1.)
¿We have developed a method,¿ Anderson added, ¿that we believe can be used to track different changes in West Nile virus, not only in Connecticut, but through North America as the virus moves. By now, this pathogen has already been detected or isolated from more than 70 species of birds in North America that are susceptible to West Nile virus. So it¿s not just crows. The virus ranges out of birds into humans when you have a mosquito that feeds on both birds and mammals.
¿As of Nov. 2, 2001,¿ Anderson noted, ¿just a week ago, data from the CDC [Centers for Disease Control & Prevention] count a total of 37 human cases of West Nile disease this year, reported in seven states: Florida, 10; Maryland, 6; New Jersey, 6; New York, 6; Connecticut, 6; Pennsylvania, 3; Georgia, 1. Of the six cases in Connecticut in 2001,¿ he noted, ¿one died and one is still hospitalized. These were primarily people 60 years of age or older. There were not many deaths this year; the one in Connecticut and one in Georgia.¿
Anderson and his co-authors collaborated with immunologist Erol Fikrig at Yale University to develop a vaccine against West Nile infection. (Fikrig is a major developer of the Lyme disease vaccine.) They genetically engineered an antigenic protein in the virus and injected it into uninfected mice. Immunization with the vaccine provided complete protection from the viral envelope, as they reported in the Journal of Immunology dated Nov.1, 2001. It¿s titled: ¿Immunization of mice against West Nile virus with recombinant envelope protein.¿
A Vaccine With A Warning Label
Fikrig considers West Nile virus ¿an emerging disease.¿ A co-author of his and Anderson¿s paper is Raymond Koski of L2 Diagnostics Inc. in New Haven, a biotech company involved in developing the vaccine. Fikrig concludes his paper with the caveat: ¿Epidemiological and ecological studies on West Nile virus in the U.S. over the next few years will determine the overall risk of acquiring WN virus infection and subsequent encephalitis, and whether a vaccine-based approach toward disease prevention is warranted.¿
Anderson is also working with a physician, James Rahal, who is director of infectious diseases at New York Hospital in Queens. ¿We have prepared a short, pending paper that reports evaluation of a protocol we are developing for therapeutic treatment of West Nile disease,¿ Anderson concluded.