West Nile Virus Infections May Prove Deadlier Than Previously Thought

At the American Society of Tropical Medicine & Hygiene (ASTMH) Conference on November 14, 2016, scientists from Baylor College of Medicine and Texas Children’s Hospital presented research indicating that infection with West Nile virus may be linked with a shorter lifespan.

Researchers continue to learn more about West Nile virus and its distressing effects. Principal author on the study, Kristy O. Murray, DVM, PhD, was quoted in a press release as saying, “While we understand the current focus on Zika virus, for many people in the United States today, West Nile virus is the much more serious mosquito-borne threat, and that threat may persist even for patients who appear to have survived the infection unscathed.”

For their research study, the scientists reviewed 4,144 cases of West Nile virus infection in Texas that occurred between 2002 and 2012. They focused on acute deaths that were recorded within 90 days of infection, as well as those who recovered from a West Nile virus infection months or years prior, but still died sooner than their peers of good health. The researchers found that although 286 individuals had died within the 90-day period after infection (the acute phase), 268 individuals had survived the infection, but still died earlier than they would have had they been otherwise healthy. The researchers referred to this as “delayed mortality” due to the virus.

After combining the acute deaths with the delayed deaths, the researchers determined that West Nile virus had a 13% fatality rate (554/4,144 over a 10-year period). This rate is higher than the 4% national fatality rate predicted by the Centers for Disease Control and Prevention (CDC) between 1999 and 2015. The low rate highlighted by the CDC only accounted for acute deaths; it did not include those that were potentially delayed.

According to Dr. Murray, this was the largest study to date investigating what healthcare providers have seen in smaller groups of West Nile-infected patients: which is that the virus appears to be capable of causing health problems after an individual is recovered from the initial infection. “For several years, we had followed smaller groups of patients and felt that many had died prematurely,” Murray said.

For each patient included in the study, the scientists had access to information about the course of the patient’s initial infection and information from the Texas state death registry on the cause of death. According to Dr. Murray, the patients who experienced a delayed death “had suffered significant neurological complications during the acute phase of their illness” and kidney disease was “statistically found to be a significant cause of death.” Researchers have long thought kidney disease to be a long-term complication of a West Nile virus infection.