Q. What did the study find?
A. The study found West Nile virus RNA (genetic material) in the urine of five of 25 patients tested. These patients had been diagnosed with West Nile virus encephalitis (infection of the brain) between 2002 and 2007. The five who tested positive all had a history of high blood pressure. Some of the five patients complained of ongoing symptoms like feeling weak or tired, or having problems with their memory. It is not known if these symptoms were related to their West Nile virus infection. Attempts to grow the virus from urine of these five patients were not successful.
Q. Can people have persistent infection with West Nile virus?
A. The findings of this study suggest that, in some people, West Nile virus may persist in the kidneys. There have been a few reports of persistent West Nile virus found in brain, spinal fluid, and blood of people who had problems with their immune system. All people in the recent study had West Nile virus encephalitis (infection of the brain) during their initial illness. It is not known how many people who have had West Nile virus encephalitis might have persistent West Nile virus in their urine. It is also not known if people who have had West Nile fever or asymptomatic West Nile virus infection can have similar findings. Further studies are planned to address these questions.
Q. I still have symptoms many months or years after I was diagnosed with West Nile virus disease. Does this mean that the virus is still present in my body and causing these symptoms?
A. At this time, West Nile virus RNA (genetic material) has been detected in the urine of five of 25 patients tested several years after their West Nile virus disease. Attempts to grow the virus from these patients were not successful. More studies are needed to confirm these findings and to see if persistent West Nile virus infection is related to ongoing symptoms. If you are having symptoms that cause you concern you should speak with your health care provider.
Q. Is there any treatment for West Nile virus infection?
A. No. At this time, there is no specific treatment for West Nile virus infection.
Q. Can persistent West Nile virus RNA (genetic material) in the body cause medical problems like high blood pressure or kidney disease?
A. This is not known. In the recent study, all five patients who had West Nile virus RNA found in their urine were older men with high blood pressure. The high blood pressure was found prior to their initial West Nile virus disease, so it is unlikely that their blood pressure problems were caused by West Nile virus. One patient had developed kidney disease since his initial West Nile virus infection in 2002. It is not known if the kidney disease was related to West Nile virus or other medical problems. A larger study is needed to figure out if persistence of West Nile virus may lead to certain medical problems.
Q. Can my doctor test my urine to find out if I am still infected with West Nile virus?
A. No. There is no approved test to look for West Nile virus RNA (genetic material) in urine. In addition, the meaning of finding West Nile virus RNA in urine is unknown. For these reasons, urine should not be tested for West Nile virus RNA as part of routine medical care. Further studies will be done to figure out the importance of the findings from this study.
If you have symptoms that you think are related to a past West Nile virus infection, you should consult your health care provider. Depending on your symptoms and other medical conditions, your health care provider can work with you to consider possible causes and treatments.
Q. (For healthcare providers) Can I have my patient’s urine tested for West Nile virus?
A. No. The test that was performed in the study was experimental and is not available for routine use. There are commercially available tests for West Nile virus RNA (i.e. WNV RT-PCR). However, the sensitivity and specificity of WNV RT-PCR on urine is unknown. In addition, the meaning of a positive test result in urine is unknown. For these reasons, it is not recommended that RT-PCR testing be performed on urine. Further clinical studies will be done to evaluate the clinical significance of the findings from this study.
Q. Can I be an organ donor if I was previously infected with West Nile virus?
A. Yes. You can still become an organ donor if you have had West Nile virus infection in the past. At this time, most organ donors are not screened for West Nile virus.
Q. Can I be a tissue donor if I was previously infected with West Nile virus?
A. Yes. You can still become a tissue donor if you have had West Nile virus infection in the past. Tissue donors are not usually screened for West Nile virus.
Q. Can I be a blood donor if I was previously infected with West Nile virus?
A. Yes. You can still be a blood donor if you have had West Nile virus infection in the past. All donated blood in the United States is screened for West Nile virus RNA (genetic material). If West Nile virus RNA is found in your donated blood, it will not be given to anyone and you will be asked to not donate blood for 120 days.
You should not donate blood if you are unwell or have a fever.
Q. What is CDC doing to better understand the issue of persistent West Nile virus infection?
A. CDC is working with researchers to confirm that persistent West Nile virus infection occurs. If confirmed, CDC will look at how many people with West Nile virus disease develop persistent infection. The medical importance of persistent West Nile virus infection will also be studied. These studies will address if additional testing of certain groups should be done.
These questions and answers will be updated as more information becomes available.
