WEST NILE STORY, a timely book by Dickson Despommier, PhD, Professor of Public Health and Microbiology at Columbia University, describes the two West Nile virus (WNV) epidemics in New York City in the summer of 1999.
The first few pages of the book are reminiscent of past articles by Berton Roueche published in The New Yorker. Each story always began with the description of a mysterious illness and often deaths of multiple people. This led to a detective-like approach of clinicians and scientists who ferreted out the cause of disease, usually an infectious agent or toxin. Many of those articles were published in an extraordinarily enjoyable book entitled Eleven Blue Men and Other Narratives of Medical Detection, published by Little, Brown in 1953.
Like Roueche, Dr. Despommier opens West Nile Story with the clinical features of the illness and then chronicles the detective work that followed. This required epidemiological statistics of human deaths as well as information on birds that were dying from WNV infection.
OUTBREAK IN 1999
West Nile Story details the 1999 outbreak of encephalitis in New York City that affected 65 people, most over age 50 years, six of whom died. There were also four deaths in New York, New Jersey, and Connecticut in 2000, and five more deaths in states along the East coast of the United States in 2001. The epidemic also affected birds, particularly crows.
Experts in infectious disease analysis initially attributed the disease to St. Louis encephalitis virus. But rapid and more accurate work by Dr. Ian Lipkin, a neurologist and virologist formerly at the University of California-Irvine School of Medicine, and now at the Columbia University School of Public Health in New York City, identified the virus as WNV, a member of the genetically-related family of flaviviruses. “Flavi” means “yellow” – the most well-known member of this family is the virus that causes yellow fever.
Shortly after the human deaths caused by WNV, the Centers for Disease Control and Prevention in Atlanta recognized that the same WNV was killing hundreds of birds in the New York City area. Dr. Despommier explains how the hot dry climate in New York City in 1999 drove birds to the Bronx River section of the city, where the displaced birds encountered WNV-infected mosquitoes.
Birds are intermediate hosts for the virus, between mosquitoes and humans. After birds began to die from WNV, the mosquitoes switched to humans for their blood meal. Most cases of WNV encephalitis were based in Queens, a borough of about two million people, including 400,000 over age 60. Most WNV deaths were in elderly individuals, who are most susceptible to WNV infection.
GENESIS OF VIRUS
Dr. Despommier provides a clear, easy-to-read description of WNV and its genesis. WNV is a single-stranded RNA virus that was first identified in the West Nile district of Uganda in 1937. Since its discovery in Africa, WNV has been found in many other regions, including the Middle East, Europe, Russia, India, Indonesia, and most recently North America.
In the book, Dr. Despommier points out that virus replication has been shown to be slower in colder temperatures and accelerated at higher temperatures. As WNV infection increases in a population, its host and geographic range are likely to change. Thus, the author writes, it will be important to identify the species of mosquito that carries WNV and to work toward eradicating that species in particular.
Ultimately, 1,900 people in New York City were infected with WNV, although only a few became ill. A particularly interesting observation is that WNV can be transmitted among crows without a mosquito as the intermediary.
The crows are thought to be the predominant bird infected because they are highly social and are likely to live around residential areas. Although the geographical origin of the WNV that caused disease in New York City in 1999 is uncertain, sequence analysis showed that the strain in North America is closely related to other human epidemic strains isolated from Israel, Romania, Russia, and France.
FOCUS ON MOLECULAR PATHOGENESIS
The worldwide AIDS epidemic led to rapid intense research on HIV that resulted in more knowledge about the molecular pathogenesis of HIV than is known for any other virus. If West Nile virus infection continues to spread as it has, we can expect that research on its molecular pathogenesis will also be concentrated and speedy. Fortunately, most West Nile virus infections in humans are subclinical and do not cause encephalitis.
Because West Nile virus infection spread to the central and western part of the United States in the summer of 2002, and most recently was incriminated as a cause of encephalitis in blood transplant recipients, laypeople, as well as physicians, have become increasingly attentive to new outbreaks of disease in animals and humans.
While this book will interest clinicians, virologists, and epidemiologists primarily, the informed layperson will also enjoy it, and all readers will learn a great deal. The neurologist who curls up with this book for a few evenings (it can be read in about two hours) is likely to find other family members doing the same soon enough.