West Nile virus (see DDP Newsletter July 2003) continues its march across the United States. You can track its progress and the casualties in your area at westnilemaps.usgs.gov. Surveillance data appear weekly in Morbidity and Mortality Weekly Report (www.cdc.gov/mmwr). The virus has become so widespread that only exceptional items and extensions of geographic range or host species are reported at www.promedmail.org. The extent of human infections is not known because most state health departments are testing only the 1% of individuals with the most severe infections, those hospitalized with encephalitis.
``You only really need 100 percent reporting when an illness can be passed from person to person. West Nile isn't,'' stated Eskild Petersen, M.D., University of Arizona infectious disease specialist (Ariz Daily Star 9/26/03).
Dozens of horses are being put down in Cochise County, AZ, reported a patient at St. Elizabeth of Hungary Clinic in Tucson. He reported flu-like symptoms but could not afford the $112 for a commercial test; the health department refused to test him, saying nothing could be done if the test was positive.
The Marion County (Indiana) Health Department evidently holds a different view. Upon receiving a report of a probable case, the county sprayed an area in a one-mile radius around the person's home. (Mosquitoes can reportedly travel 3 miles.) ``We can't sit around and wait for someone to confirm [the report],'' stated Rick Mack, a supervisor in the county's mosquito control program.
Mosquitoes are apparently being left alone in Cochise County, and advice on pesticides or widespread spraying is conspicuously absent from the CDC's list of suggestions, though present in some links added Sept. 12. The use of adulticides is a much lower priority than public information campaigns exhorting people to wear long-sleeved shirts and empty the birdbath, and is heavily regulated. Yet waiting for human cases to appear before using adulticides allows infective adult mosquitoes to maintain transmission during the 3 to 12-day WNV incubation period, states Joseph Conlon of the American Mosquito Control Association. Even a 30% kill rate of the vectors has a significant impact on disease transmission, he argues.
The CDC is highly deferential to environmental activists, who have attacked the killing of mosquitoes as ``disrupting the food chain.'' After all, declares literature of the New York Green Party, ``these diseases only kill the old and people whose health is already poor'' (Miller HI, Tech Central Station 8/14/03).
WNV has now been reported in alpacas in Colorado, raising concerns that more animals are vulnerable than had been previously thought. Dogs, cats, and pigs, which are not tracked by the state, are probably infected at a high rate though they usually show no symptoms, stated Richard Bowen, a professor of biomedical sciences at Colorado State University (Aberdeen News 8/18/03).
As WNV spread to the point that it may be out of control, public health departments have mainly engaged in surveillance. Meanwhile, malaria could also be reintroduced into the U.S. Eight cases of indigenously acquired malaria have occurred in Palm Beach County, FL, over 3 months and several mosquito life cycles (Sun-Sentinel 9/29/03). Genetic typing supports the hypothesis that all cases originated from a single infected person. This is the first outbreak with extended transmission reported in the U.S. since 1986. Malaria eradication was certified in the U.S. in 1970-before DDT was banned-although there is a global malaria burden of 300-500 million cases and 1 million deaths annually (www.promedmail.org 9/25/03).
The most prestigious scientific publications still cite the ban on DDT as a triumph for the environment (Nature 2003;301:1187-1188), but calls to bring back our most effective weapon against the most dangerous animal in the world are now being heard (Hart B, OC Register 6/27/03, Ambrose J, Ariz Daily Star 8/14/03).
Public concern about smallpox has waned now that Saddam Hussein's purported weapons of mass destruction have not been found. The reason for Iraqi interest in smallpox vaccine in the 1990s remains unknown, and Russia's refusal to share smallpox and other lethal germ strains for U.S. study apparently stands (Miller J, NY Times 12/3/02).
Public health authorities who downplay risks of other vaccines-including death and permanent brain damage-warn about serious risks of the smallpox vaccine and its potential to undermine confidence in other vaccines (Science 2002;298:2312-2316). An in-depth discussion of risks and benefits is provided in the Jan. 30, 2003, issue of The New England Journal of Medicine. Models of the effects of targeted versus mass vaccination are discussed (Science 2002;298:1428-1432, 1342-1344 and 2003;300:1503-1504). A safer vaccine is under development (Wall St J 12/24/02).
Although five heart attacks, three fatal, within 5 to 17 days of vaccination were widely reported, these were probably coincidental. Myocarditis probably is a rare adverse effect of the vaccine. It is generally mild, although four deaths from this cause have been reported since 1947 in the U.S., Britain, Finland, and Australia.
Experience with the military vaccination program suggests that ``broad smallpox vaccination programs may be implemented with fewer serious adverse reactions than previously believed'' (JAMA 2003;289:3278-3282), although myopericarditis occurred at a rate of 1 in 12,819 primary vaccinees (JAMA 2003;289:3283-3289). No cases occurred in previously vaccinated persons. Only one other moderate or serious vaccine-related reaction occurred, a case of encephalitis. In 450,293 vaccinees, there were 36 cases of mild generalized vaccinia, 1 of erythema multiforme, 48 of inadvertent self-inoculation (10 to the eye), and 21 of vaccinia transfer to a contact. All were substantially less than historically reported. In 36,217 vaccinations of civilians between Jan. 24 and May 9, 2003, 18 suspected and 6 probable cases of myopericarditis, 1 case of encephalitis, 1 suspected and 1 confirmed case of generalized vaccinia, 9 suspected and 4 confirmed cases of ocular vaccinia, and 1 suspected and 2 confirmed cases of progressive vaccinia have been reported (MMWR 5/23/03).
The risk of death from vaccination in persons age 15 and older, without historical risk factors, is calculated to be about 1 in 5,000,000. The risk of death of an unvaccinated person from transmission of vaccinia is about 1 per 11,000,000 vaccinated persons. The risks of everyday living are 42,000 times higher than the risk of vaccination (Bicknell WJ, Bloem KD, Cato Institute Briefing Paper no. 85, 9/5/03). These authors conclude that the CDC overstates the risk of vaccination, while understating the difficulty of rapid vaccination after an attack.
``No one has epidemic-control experience with smallpox in a nonimmune, highly mobile population where exposure will be malicious,'' they write. The risk of attack is a national security, not a public health estimate. There are many potential sources of virus, and North Korean troops have reportedly been vaccinated.
The greatest risk is from transmission to immunocompromised patients. Though the CDC recommends use of a semipermeable dressing only in medical personnel, Bicknell and Bloem suggest use of Tegaderm+Pad from 3M or OpSite from Smith & Nephew in all vaccinees. This decreases virus shedding by 95%; 99% if two layers are used (ibid.)
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