Sep 8, 2004 (CIDRAP News) – West Nile fever, usually considered a relatively benign manifestation of the mosquito-borne West Nile virus, can be a prolonged, serious illness, according to a study published Sep 7 in the Annals of Internal Medicine.
The authors, led by John T. Watson, MD, MSc, of the Chicago Department of Public Health, write that most West Nile studies have focused on patients who contract meningitis or encephalitis. However, three serologic studies in the United States and Romania showed that those conditions occur in only about 1 in 150 infected people, the researchers note. Of the approximately 20% of infected people who have symptoms, most have West Nile fever only.
West Nile fever is generally described as a febrile illness of sudden onset lasting 3 to 6 days, with malaise, anorexia, nausea, vomiting, eye pain, headache, sore muscles, and rash. Interviews with 98 Illinois residents who contracted nonparalytic West Nile fever in 2002, however, revealed a more debilitating, longer-lasting illness.
The authors located former West Nile patients through public health agency records. The Illinois Department of Public Health tested cerebrospinal fluid and blood specimens submitted for suspected arboviral infection in 2002 and notified local health authorities of the results. People with positive results who didn’t have paralytic fever, meningitis, or encephalitis were considered to have West Nile fever; 331 cases met this definition. One hundred forty of those people lived in the jurisdictions of cooperating health departments. Of that number, the authors were able to contact and interview 98.
The authors report that 63% of the respondents said they had symptoms for at least 30 days, and the median time for full recovery was about 2 months. Fatigue was the most commonly reported symptom. Ninety-four respondents said they had felt exhausted for a median of 36 days. More than half of respondents reported fever, headache, muscle pain, muscle weakness, rash, neck pain or stiffness, and difficulty concentrating, the study said. The median duration of muscle weakness was 28 days.
West Nile fever also kept people home, causing 57 respondents to miss a median of 10 days of work or school. Thirty respondents had been hospitalized, with a median stay of 5 days. The rest received outpatient medical care, and nine people reported having physical or occupational therapy.
The researchers suggest that the severe illness reported might be due to changes in the virus. They recommend mandatory reporting of West Nile fever to facilitate timely public health interventions such as mosquito control.
Watson J, Pertel P, Jones R, et al. Clinical characteristics and functional outcomes of West Nile fever. Ann Intern Med 2004:141(5):360 [Abstract]