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| |  West Nile Virus May Persist in Kidneys Years After Infection ARLINGTON, Va -- December 8, 2009 -- People who have been infected with West Nile virus may have persistent virus in their kidneys for years after initial infection, potentially leading to kidney problems, according to a study published in the January 1 issue of The Journal of Infectious Diseases. Prior to this latest research, it was thought individuals remain infected with West Nile virus only for the first few days of illness. The study, led by Kristy Murray, PhD, University of Texas School of Public Health, Houston, Texas, demonstrates that not all individuals clear the virus from their system within the first few days -- and that it can remain in the kidneys for years, potentially leading to kidney failure. Dr. Murray and colleagues followed more than 100 patients with severe initial West Nile virus infections for 7 years. Individuals were evaluated and blood samples collected every 6 months. More than half of the patients continued to have infection-related symptoms years after their initial illness, although symptoms began to plateau around 2 years after infection. The deaths of 5 patients due to kidney failure led researchers to consider whether the kidney could be a preferred replication site for the virus. To test this hypothesis, the researchers collected urine samples from 25 patients from their original cohort and tested them for presence of West Nile virus. In this group, 5 (20%) patients tested positive for the virus. Viral RNA could be detected in the urine for at least 6 years following infection. Four of the 5 patients who tested positive also experienced chronic symptoms. Of these 5, 1 patient developed kidney failure. These results show that West Nile virus is capable of long-term persistence in patients, particularly when chronic symptoms are present. In an accompanying editorial, Ernest Gould, PhD, Centre for Ecology and Hydrology, Oxford, United Kingdom, pointed out that this study raises the additional concern that West Nile virus and other flaviviruses may be transmitted to mosquitoes by apparently healthy humans or animals. This possibility has the potential to start epidemics in new regions of the world. According to Dr. Murray, patients who have been infected with West Nile virus should “have their kidneys monitored by their physician for any evidence of disease and be aware that persistent infection of the kidneys can happen.” Dr. Murray also advises people to take proper precautions to protect themselves from mosquito bites during transmission seasons, typically the summer and fall, to avoid infection. More research is needed to “understand the underlying mechanisms related to the shedding of virus particles in urine, whether shedding of the virus is constant or intermittent, and whether or not this represents true infection resulting in kidney disease,” the study authors write. They continue to evaluate all study participants, particularly in regard to kidney function. In addition, they are focusing on developing treatment options for those who remain infected with the virus.
SOURCE: Infectious Diseases Society of America
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