West Nile in Your Kidneys? Really?

indigo girl · Dec 9, 2009

In order to study natural history you need to follow people who have been infected and see what happens to them over time. Early on it appeared that either you got sick and died or you got over your infection. Then some cases turned up that seemed to have prolonged effects. And now we are finding that some of those who are apparently recovered may be harboring persistent infection.
Studies in monkeys and hamsters had already shown that WNV could persist in brain tissue and in the hamsters was also found in the kidney. The hamsters continued to shed virus in their urine up to 8 months. Now it appears the same is true of people. The Houston group has now followed 100 cases of severe WNV infection for 7 years, and while symptoms decreased over that time they seemed to level out at 2 years. As noted above, more than half were still having symptoms after 5 years. But five of them died of kidney failure, and putting that together with the hamster studies made the Texas researchers look at the urine of a sample of 25 from the cohort of 100. 5 of them, or 20%, seemed to be shedding virus in the urine. The evidence was in the form of entire viral genomic material. So far no virus has been isolated. But the length of time that genetic material is being shed indicates that virus is still being formed. So this is persistent infection.
WNV if now the most common arbovirus (arthropod borne virus) infection in the US. It may turn out to be a significant cause of kidney failure, although that is still unclear. What's intriguing (and worrying) is that we still don't have good fix on the epidemiology of this disease. We have assumed that significant levels of virus in the blood (viremia) of infected animals (birds) was required for a mosquito to have a large enough viral load to infect a human. That's why infected people didn't pass it on to others by having a mosquito bite both of them. But if the virus is present in other tissues there might be other modes of transmission. In an accompanying editorial by Ernest A. Gould of the Centre for Ecology and Hydrology, Oxford (UK) raised that issue:

More at: http://scienceblogs.com/effectmeasure/2009/12/west_nile_virus_in_your_kidney.php#more

The Editors of Effect Measure are senior public health scientists and practitioners. Paul Revere was a member of the first local Board of Health in the United States (Boston, 1799). The Editors sign their posts "Revere" to recognize the public service of a professional forerunner better known for other things.