Shiloh
Editor, Senior Moderator
Source: http://www.eht-forum.org/news.html?fileId=news091211062239&from=home&id=0
Friday 11 December 2009
West Nile fever persists in kidneys
?Compelling evidence? that West Nile virus lingers in kidneys raises questions over organ donation risk
Source: CDC/James Gathany
People affected by West Nile fever may harbour the virus in their kidneys for years after their illness runs its course, report1 health scientists in Clinical Infectious Diseases. Some experts worry that this could put patients receiving kidney donations at risk.
?We report here for the first time? that West Nile virus is capable of long-term persistence in patients,? write Kristy Murray and colleagues from the University of Texas, USA, in the January edition of the journal. ?The public health impact of these findings is considerable.?
West Nile fever is endemic in Africa, Asia and the Middle East but appeared in the USA for the first time in 1999. Since then, around 25,000 cases of the disease have been reported in the country. The virus usually circulates in birds but can be transmitted to people through the bite of an infected mosquito.
Infection with the virus is usually self limiting, but in some people it can develop into meningitis or encephalitis. Experiments in hamsters have suggested that the virus can persist in the brain and kidney for months. To see what happens in people in the years after infection has occurred, the researchers collected urine samples from 25 patients who had been hospitalised with the virus from 2002 to 2008.
Molecular analysis revealed fragments of West Nile virus RNA in the samples collected from five people, including three who became infected more than six years earlier, the authors explain. Four of the five people reported chronic symptoms of weakness, tiredness and memory loss, and one went on to develop kidney failure, they add.
Ernest Gould, from the Centre for Ecology and Hydrology in Oxford, UK, says the evidence presented by the researchers is ?compelling?. ?The report? begins to provide robust evidence for West Nile virus persistence in humans,? he writes in an associated editorial2.
It also raises the possibility that mosquitoes could pick up the virus from apparently healthy people, sparking outbreaks of the disease in new parts of the world, says Gould.
But Luisa Barzon, from the University of Padova in Italy does not believe this is likely to happen. Low viraemia in these patients means that few viruses can travel from the kidney into the bloodstream, where they become available for a mosquito to pick up. ?However, direct inter-human transmission through kidney transplantation from an infected donor or through blood donation could be possible,? she says.
Blood and organ donors in the USA are not currently tested for West Nile virus. Instead, health staff typically ask a series of questions to flag up any potential risk. Several cases of West Nile encephalitis have developed in people receiving donated organs in the USA. Health authorities say routine testing for the virus in blood is not practical because the procedure is too time consuming, and the reliability of the test is still unproven.
References and links
1.
Murray K, Walker C, Harrington E, Lewis JA, McCormick, Beasley DWC, et al. Clin Infect Dis 2010, 201:2?4. doi: 10.1086/648731
2.
Gould E. West Nile virus: don?t underestimate its persistence. Clin Infect Dis 2010, 201:1. doi: 10.1086/648732
World Health Organization information about West Nile virus
]US Centers for Disease Control and Prevention[/URL information about West Nile virus and blood and organ donations
Friday 11 December 2009
West Nile fever persists in kidneys
?Compelling evidence? that West Nile virus lingers in kidneys raises questions over organ donation risk
Source: CDC/James Gathany
People affected by West Nile fever may harbour the virus in their kidneys for years after their illness runs its course, report1 health scientists in Clinical Infectious Diseases. Some experts worry that this could put patients receiving kidney donations at risk.
?We report here for the first time? that West Nile virus is capable of long-term persistence in patients,? write Kristy Murray and colleagues from the University of Texas, USA, in the January edition of the journal. ?The public health impact of these findings is considerable.?
West Nile fever is endemic in Africa, Asia and the Middle East but appeared in the USA for the first time in 1999. Since then, around 25,000 cases of the disease have been reported in the country. The virus usually circulates in birds but can be transmitted to people through the bite of an infected mosquito.
Infection with the virus is usually self limiting, but in some people it can develop into meningitis or encephalitis. Experiments in hamsters have suggested that the virus can persist in the brain and kidney for months. To see what happens in people in the years after infection has occurred, the researchers collected urine samples from 25 patients who had been hospitalised with the virus from 2002 to 2008.
Molecular analysis revealed fragments of West Nile virus RNA in the samples collected from five people, including three who became infected more than six years earlier, the authors explain. Four of the five people reported chronic symptoms of weakness, tiredness and memory loss, and one went on to develop kidney failure, they add.
Ernest Gould, from the Centre for Ecology and Hydrology in Oxford, UK, says the evidence presented by the researchers is ?compelling?. ?The report? begins to provide robust evidence for West Nile virus persistence in humans,? he writes in an associated editorial2.
It also raises the possibility that mosquitoes could pick up the virus from apparently healthy people, sparking outbreaks of the disease in new parts of the world, says Gould.
But Luisa Barzon, from the University of Padova in Italy does not believe this is likely to happen. Low viraemia in these patients means that few viruses can travel from the kidney into the bloodstream, where they become available for a mosquito to pick up. ?However, direct inter-human transmission through kidney transplantation from an infected donor or through blood donation could be possible,? she says.
Blood and organ donors in the USA are not currently tested for West Nile virus. Instead, health staff typically ask a series of questions to flag up any potential risk. Several cases of West Nile encephalitis have developed in people receiving donated organs in the USA. Health authorities say routine testing for the virus in blood is not practical because the procedure is too time consuming, and the reliability of the test is still unproven.
References and links
1.
Murray K, Walker C, Harrington E, Lewis JA, McCormick, Beasley DWC, et al. Clin Infect Dis 2010, 201:2?4. doi: 10.1086/648731
2.
Gould E. West Nile virus: don?t underestimate its persistence. Clin Infect Dis 2010, 201:1. doi: 10.1086/648732
World Health Organization information about West Nile virus
]US Centers for Disease Control and Prevention[/URL information about West Nile virus and blood and organ donations