West Nile virus can persist in kidney

HOUSTON, Dec. 14 (UPI) -- The West Nile virus may persist in kidneys years after infection, U.S. researchers say.

Study leader Kristy Murray of the University of Texas School of Public Health in Houston says -- contrary to previous thought -- not all individuals cleared the virus from their system within the first few days after infection.

The seven-year study, published in the Journal of Infectious Diseases, analyzed blood samples every six months of more than 100 Houston patients infected with severe West Nile virus.

Symptoms persisted for years in more than half of the study patients but tended to plateau after two years, Murray says. However, five study participants died due to kidney failure.

To further evaluate whether the kidney could be a replication site for the virus, Murray and colleagues tested urine samples from 25 patients from the original cohort.

They say five patients -- 20 percent -- tested positive for the virus and viral RNA could be detected in the urine for at least six years following infection. Four of the five experienced chronic symptoms and one patient developed kidney failure.