Stanford University study shows Ebola virus may infect people who show no symptoms

According to a new study conducted by the Stanford University School of Medicine, approximately 25 percent of individuals in a Sierra Leone village were infected with Ebola virus disease but showed no symptoms, which suggests a broader transmission of the virus than originally thought.

The Stanford researchers identified 14 individuals in the village previously unknown to have had the disease one year after the Ebola epidemic spread through various parts of West Africa.

This development, the researchers say, confirms previous suspicions that the Ebola virus does not uniformly cause severe disease and that people may be infected without showing any signs of the illness. The findings also suggest that the virus’ spread may have been far wider than originally thought. The researchers calculated that the virus may be minimally symptomatic in up to 25 percent of all people in affected areas.

“The study corroborates previous evidence that Ebola is like most other viruses in that it causes a spectrum of manifestations, including minimally symptomatic infection,” Dr. Gene Richardson,a former fellow in the Division of Infectious Diseases and Geographic Medicine at Stanford who is now a PhD candidate at the university.

“It provides important evidence on that front,” he added. “It also means a significant portion of transmission events may have gone undetected during the outbreak. This shows there was a lot more human-to-human transmission than we thought.”

The findings were published in the Nov. 15 issue of PLOS Neglected Tropical Diseases and were presented on Nov. 14 at the American Society of Tropical Medicine and Hygiene’s annual meeting.