In the United States thousands of cases are reported a year, with most occurring in August and September. It can occur in outbreaks of disease. Severe disease may also occur in horses, for which a vaccine is available. A surveillance system in birds is useful for early detection of a potential human outbreak. Signs and symptoms
About 80% of those infected with West Nile virus (WNV) show no symptoms and go unreported. About 20% of infected people develop symptoms. These vary in severity, and begin 3 to 14 days after being bitten. Most people with mild symptoms of WNV recover completely, though fatigue and weakness may last for weeks or months. Symptoms may range from mild, such as fever, to severe, such as paralysis and meningitis. A severe infection can last weeks and can, rarely, cause permanent brain damage. Death may ensue if the central nervous system is affected. Medical conditions such as cancer and diabetes, and age over 60 years, increase the risk of developing severe symptoms.Headache can be a prominent symptom of WNV fever, meningitis, encephalitis, meningoencephalitis, and it may or may not be present in poliomyelitis-like syndrome. Thus, headache is not a useful indicator of neuroinvasive disease. West Nile fever (WNF), which occurs in 20 percent of cases, is a febrile syndrome that causes flu-like symptoms. Most characterizations of WNF describe it as a mild, acute syndrome lasting 3 to 6 days after symptom onset. Systematic follow-up studies of patients with WNF have not been done, so this information is largely anecdotal.
Conservative
The conservative treatment consists of observation in time. Studies show that the trigger thumb spontaneously resolves in 49 months. According to Leung et al., trigger thumbs in infants resolve spontaneously in 63% of the cases. No residual deformities were found and there is no recurrence once resolved. Residual deformity is defined as persistent flexion deformities of the thumb and radial deviation at the IPJ. Extension exercises and splinting can be added to the observation. These two elements have favourable results in improvement in flexion impairment of the thumb. However, compared to observation, the benefit of merely extension exercises and splinting are still unclear.It has been recommended to attempt conservative treatment first, before attempting surgical treatment. Surgical
Surgical treatment should be considered when the patient has a trigger thumb bilaterally and when the patient has a severe trigger thumb. Severe is defined as when the thumb is locked so that the thumb cannot be flexed or extended either passively or actively. Surgical treatment should also be considered when observation and/or splint therapy has not achieved sufficient results after 49 months. Unlike the surgical treatment given for adults, which is unambiguously a surgical release of the A1 pulley of the thumb, the optimum surgical treatment for infants has not yet been discerned. In case of infants, research has shown that only in 15% of the cases A1 pulley release alone is sufficient.