Disease researchers in Atlanta today announced the results of a study that found that West Nile virus is more dangerous than previously believed, with a mortality rate more than triple what the Centers for Disease Control and Prevention previously tallied.
"For many people in the United States today, West Nile virus is the much more serious mosquito-borne threat,” said Dr. Kristy Murray, a professor at Baylor College of Medicine and Texas Children’s Hospital, the principal author of the study. "And that threat may persist even for patients who appear to have survived the infection unscathed."
The study, which used Texas infections between 2002 and 2012 as its data set, found that people were dying from the disease long after doctors had declared them free of infection. The authors of the yet-unpublished study presented the news at the 2016 Meeting of the American Society of Tropical Medicine and Hygiene. According to an ASTMH release:
The researchers found there were 286 people who died in the acute phase of WNV. But after examining causes of deaths and symptoms from the initial infection, Murray and her colleagues concluded that 268 people who survived infection subsequently died early (they call it “delayed mortality”) due to the virus.
In the 2012 breakout in Texas, West Nile infected 4,114 people.
Any death attributable to the disease after 90 days qualifies as a delayed death, anything before is called an acute death. Counting the fatal acute and delayed cases, the researchers attributed 554 deaths to West Nile virus during the 10-year period — a 13 percent fatality rate.
That’s much higher than the 4 percent national fatality rate for West Nile the CDC recorded between 1999 and 2015, the researchers say.
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Murray's team has confidence in the study because they had access to information about the initial infection and records maintained by Texas that document cause of death. “For several years, we had followed smaller groups of patients and felt that many had died prematurely,” Murray said in the release. “We saw many people who were otherwise healthy until they had West Nile virus — and then their health just went downhill.”
Most of these "delayed" deaths actually didn't occur much longer after the outbreak, but researchers said that some effects manifested up to 10 years later. This is particularly true of kidney damage which, the release notes, "was statistically found to be a significant cause of death." These problems beset patients over and under 60 years old.
On Tuesday Dallas County reported the 53rd West Nile infection for the 2016 season: