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FINDINGS: Nuchal rigidity and seizures may occur. Flaccid or spastic paralysis may appear after the first week. [ID, p. 1291] Cranial nerve palsies occur in 1/3 of JE cases, and affected patients have facial and conjugate gaze paralysis. Other findings are abdominal pain, tremor, rigidity, cortical blindness, and leukocytosis. [PPID, p. 1939] These viruses are laboratory hazards (Biosafety Level 3 or 4). "There is a Japanese encephalitis vaccine available in the US. An equine vaccine is available for EEE, WEE and Venezuelan equine encephalitis (VEE)." [CDC: Arboviral encephalitides] EPIDEMIOLOGY: Between 1964 and 1990, 640 cases of WEE and 182 cases of EEE were reported to the CDC. With more than 10,000 cases through 1990, SLE was the most common cause of mosquito-borne encephalitis in the USA before the arrival of WNV in 1999. VEE has caused tens of thousands of cases in Central and South America, and caused about 200 deaths in Venezuela in 1962-1964. About 10,000 horses were killed by VEE in Texas in 1971. WNV caused the following cases/deaths in 2002, 2003, and 2004 respectively: 4156/284, 9862/264, 2539/100. In 2004 in the USA, about 1/2 of the WNV cases were febrile illnesses and about 1/2 were meningitis/encephalitis. The introduction of the JE vaccine in the mid-1960s caused the elimination of most human cases from Japan, Korea, and Taiwan. Throughout Asia, the vaccine led to the reduction of cases from 160,000 in 1966 to 16,000 in 1996. Since 1970, JE cases have increased in Southeast Asia, India, Nepal, and Sri Lanka. Worldwide, about 10,000-15,000 deaths caused by JE are reported annually. The risk for JE infection is highest in rural areas where flooding irrigation is practiced. [PPID, p. 1915, 1927-8; CDC WNV website; CDC Travel, p. 191) |
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