Neck Surgery Foundation Annual Meeting & OTO EXPO, being held September 19-22, 2004, at the Jacob K. Javits Convention Center, New York City, NY.
A summary of the subject matter being provided to otolaryngologist—head and neck surgeons follow:
Epidemiology:
How closer examination of the affected birds showed differing degrees of both meningoencephalitis and myocarditis, while all tested negative for the most probable avian pathogens. Isolation of a virus specific to the birds’ tissues showed similarities to West Nile virus and proved genetically identical to the virus recovered from human victims of the New York outbreak. Although previous outbreaks of WNV around the world had not been uncommon, this 1999 appearance in New York City represented its first major manifestation in the continental United States.
Virology:
That WNV is a flavivirus, composed of single-stranded RNA, which incorporates an envelope glycoprotein on its surface responsible for virus—host cell binding. As a member of the Japanese encephalitis virus serocomplex, WNV is closely related to several other flaviviruses also associated with human encephalitis—St Louis encephalitis, Murray Valley encephalitis and Kunjin virus.
Although evidence exists that the virus may have originated in the Middle East, it is still unclear how the virus finally arrived in the United States. With the viral load in humans being extremely low, transmission by an infected international traveler is highly unlikely. A more plausible culprit would be migrating birds or perhaps infected adult mosquitoes or larvae inadvertently transported on a transcontinental aircraft.
Transmission:
WNV infection most commonly occurs through the bite of the infected culicine mosquito. Transmission occurs from infected birds with adequate viral loads to mosquitoes during a blood meal, with recent literature showing infection in 146 species of bird (with crows and blue jays being most susceptible) and 29 species of mosquito in the United States. Humans, horses and the majority of other mammals carry a low and brief virus in the bloodstream incapable of infecting others, to include a biting mosquito. However, the role of the human as a “dead end” host has come into question with multiple newly described modes of transmission, to include blood transfusion, organ transplantation, breast-feeding, transplacental transmission and laboratory acquisition.
Clinical presentation:
Approximately 80 percent of those infected with WNV will have an infection without the presence of symptoms, produce an immune response, and probably never know they were infected. The vast majority displaying infection will experience West Nile fever, a mild illness that follows an incubation period of three to 14 days. This illness, which is self-limiting, lasts approximately a week and produces a fever with constitutional signs and symptoms. These complaints include headache, backache, myalgias and anorexia, also includes conditions commonly seen by the otolaryngologist, such as a roseolar (red patches) or maculopapular rash involving primarily the head, neck and trunk, which occurs in about half of these patients. Dysphagia, or difficulty in swallowing, may be a concurrent complaint in up to half of affected patients, impacting both patient comfort and nutrition.
Laboratory findings/Diagnostic measures:
Due to a low human indication of virus in the bloodstream, isolation of the virus is difficult, and diagnosis is usually dependent on IgM recognition. Studies can be performed on serum or cerebrospinal fluid (CSF) with a 90 percent IgM enzyme-linked immunosorbent assay (ELISA) detection rate beginning on the eighth day following infection). This is the most simple, cost-effective way to confirm a suspected diagnosis. IgM antibodies to WNV may persist for more than six months; therefore a positive ELISA does not always signify a recent infection (unless it’s related to analogous symptoms).
If testing is conducted at private laboratories, the health department or Centers for Disease Control (CDC) will often confirm results in their own laboratories before officially reporting WNV cases. CDC will finally report a case of WNV once a state officially reports and verifies that case to CDC.
Management: