Most infections are asymptomatic; Flu-like illness with fever, headache, and myalgia; Other symptoms are nausea/vomiting, diarrhea, and rash; Neurological symptoms in <1% of infected people; [PPID, p. 1895]
The febrile illness includes headache, myalgia, arthralgia, and GI symptoms. [CCDM, p. 675] It is estimated that about 80% of WNV infections are asymptomatic, 20% are "West Nile Fever," and less than 1% are CNS infections. Encephalitis usually occurs in people who are older or chronically ill. Flaccid paralysis is less common than meningitis or encephalitis. Paralysis may involve one extremity only; it is associated with pain but not numbness. [www.cdc.gov] The symptoms of West Nile fever are myalgia, fever, rash, lymphadenopathy, headache, weakness, backache, conjunctival injection, and pharyngitis. Other findings observed in outbreaks of WNV infections are confusion, stiff neck, diarrhea, and leukocytosis or leukopenia. Complications include pancreatitis, myocarditis, optic neuritis, radiculitis, myelitis, and hepatitis. [ID, p. 2129] A maculopapular rash occurred in about 50% of patients in one outbreak. Other findings in West Nile fever are hepatomegaly (20% of patients), splenomegaly (10% of patients), liver dysfunction, abdominal pain, cough, and fatigue. Patients with neurological disease may have paralysis, convulsions, ataxia, tremors, and rigidity. [PPID, p. 1895] Can cause a syndrome resembling poliomyelitis; Guillain-Barre syndrome has also been reported. [Cecil, p. 2165] West Nile fever: 2-6 days after mosquito bite, patient has fever, headache, arthralgia, and rash (20%) for 2-7 days. [ABX Guide]
Transmission by transfusion and percutaneous occupational exposure has been reported. WNV infections are an occupational hazard for people working outside when mosquitoes are biting. Turkey breeder farm workers have become infected with WNV, but the mode of transmission is not known. [www.cdc.gov] Birds are the reservoir for WNV. Other animals that may become infected include horses, dogs, camel, cows, donkeys, water buffalo, sheep, bats chipmunks, squirrels, rabbits, rats, and skunks. [ID, p. 2128] In America, crows and ravens are often infected; death of these birds, at a higher rate than normal, is a sentinel for the presence of West Nile virus. [Cecil, p. 2158]
For updated text and symptoms of infectious diseases, see iddx.com.