Given those data, the only way to determine whether military personnel and reservists have become infected with M. tuberculosis during their service is to test all personnel for TB shortly before and after deployment. Such testing would make it possible to trace cases of active TB to periods of military service if that is when infection occurred.

Anticipating Multiple Drug-Resistant Mycobacterium tuberculosis Infection

Some M. tuberculosis strains are resistant to one or more drugs commonly used to treat LTBI and active TB (WHO 2004). The military’s medical corps should obtain the results of available drug-susceptibility tests for M. tuberculosis in regions where troops are. WHO periodically publishes a report of such data, Resistance in the World: Anti-TB Drug Prevalence and Trends. Those reports could help the military to estimate the likelihood that a person who acquires a TB infection harbors a drug-resistant strain.

WEST NILE VIRUS INFECTION

First isolated in 1937 from a febrile woman in the West Nile Province of Uganda, West Nile virus (WNV) belongs to the Japanese encephalitis virus antigenic complex in the family Flaviviridae (genus Flavivirus) and is closely related to St. Louis encephalitis virus. WNV is a 50-nm-diameter single-stranded RNA virus with a nucleocapsid core surrounded by a host-derived lipid membrane (Campbell et al. 2002).

The first human epidemics of West Nile fever were reported in Israel and occurred in 1951-1954; 2 decades later, an outbreak was reported in South Africa. By 1991, the disease had occurred throughout Africa, south Asia, and Europe. WNV has also occurred in Australia and New Zealand, but cases there were poorly documented (Wilson 1991). Later outbreaks were reported in Tunisia (1997), the Czech Republic (1997), Italy (1998), Romania (1996, 1999), the United States (1999), France (2000), and Israel (1997-2000) (Petersen and Roehrig 2001).

The US outbreak of WNV in 1999 marked the virus’s debut in the Western Hemisphere (CDC 2005e). WNV spread rapidly from its epicenter in New York City; by 2004, 48 states and the District of Columbia had reported human cases (Table 5.9) (CDC 2005a; Nash et al. 2001). It has been found in Canada and Mexico as well (Gould and Fikrig 2004).

TABLE 5.9 Statistics on US Cases of West Nile Neurologic Disease,a 2005

Characteristic

No.

Cases of West Nile neurologic disease

1,165

Median age

57 years (range, 3 months-98 years)

Male

665 (57.1 % of WNND cases)

Deaths

85 (7.3 % of WNND cases)

Median age

75 years (range, 36-98 years)

Acute flaccid paralysis

68 (5.8%)

Median age

53 years (range, 9-84 years)

Male

39 (57.4% of paralysis cases)

Deaths

5 (7.4 % of paralysis cases)

a Defined as meningitis, encephalitis, or acute flaccid paralysis.

SOURCE:CDC 2005a.

West Nile virus was considered relatively benign to humans before the 1990s (Solomon and Cardosa 2000). WNV usually causes a self-limited illness, West Nile fever, which is



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