Convalescence after West Nile virus infection can be protracted, particularly for older adults, researchers in New York have found. Physical, cognitive and functional impairments often last more than 18 months after the initial illness.

“These findings reinforce the need for local governments in affected areas to institute widespread public health measures to safeguard against West Nile virus transmission,” Dr. Denis Nash, of the New York Academy of Medicine, and associates write in the medical journal Emerging Infectious Diseases.

Nash’s team interviewed 40 patients, ranging in age from 16 to 90 years, at 6, 12, and 18 months after they were diagnosed with West Nile in 1999.

At 12 months, only 37 percent of the subjects were considered fully recovered. Younger age was the only significant factor linked to recovery, while the severity of illness or whether it involved brain inflammation did not affect recovery.

Eighteen months after infection more than 40 percent reported difficulties with walking, muscle weakness, fatigue or insomnia, the researchers report, and 30 percent were still experiencing memory loss, confusion, depression and irritability. Functional ability seemed to reach a plateau, with no improvement after 12 months.

This information reinforces the need “for persons - especially those age 65 and over - to take precautions to avoid exposure to mosquitoes and reduce mosquito breeding sites on their properties,” Nash and his colleagues conclude.

SOURCE: Emerging Infectious Diseases, August 8, 2004.