According to a new study, some infections of Ebola are minimally symptomatic, revealing that potential cases were ignored during the 2013-2016 outbreak that originated in West Africa. The study surveyed patients from Sierra Leone from October 2015 to January 2016, collecting blood samples from infected patients and control subjects.

A “significant number of individuals” appeared to host a previously undetected Ebola infection, most of them remaining being present at a hotspot location in Sierra Leone, one year after the initial outbreak.

Many Ebola transmission events may have avoided detection during the outbreak. Photo credit: John Moore / Getty Images / IB Times
Many Ebola transmission events may have avoided detection during the outbreak. Photo credit: John Moore / Getty Images / IB Times

This may imply that Ebola is present even if the patient does not show any symptoms, which in turn means that many Ebola transmission events may have avoided detection during the outbreak, increasing the potential risk of transmission in people who have not been diagnosed with the disease.

Researchers are yet to understand Ebola fully

Researchers analyzed blood samples from 187 subjects, including 132 patients who were thought not to have been exposed to the virus and 30 survivors of the disease. 14 participants were reported to have been infected without their knowledge, while two of them reported only to have suffered from fever while they remained in quarantine. The other 12 did not show any symptoms whatsoever.

The pandemic resulted in over 28,000 reported cases of Ebola as of March 2016. Researchers noted that there are still many questions that would allow a better understanding of how the virus works and how it can be defeated. So far, evidence regarding minimally symptomatic Ebola infection is scarce, and during the time of the outbreak, it was not foreseen that Ebola could exist without manifesting itself through the patient’s pathology.

Researchers conducted a serosurvey in Sukudu, a village with no more than 1000 people which has been labeled as one of the primary places where the Ebola outbreak originated. The team analyzed the list of quarantined houses and interviewed the members of the affected families. Many of the participants had never undergone an Ebola vaccine trial. Most of the infections were revealed to have occurred for sharing a public latrine or living quarters with an infected person.

Over half of the participants were male and most of them worked as farmers or miners, due to the district of Kono being rich with diamonds.

“Our data suggest that a significant portion of Ebola transmission events may have gone undetected during the epidemic,” wrote the research team.

Ebola is already known to linger in the body even after the patient has healed, particularly in the semen of male survivors. No definitive studies are suggesting that Ebola can be sexually-transmitted, which is why researchers are still trying to determine the circumstances that lead Ebola not to manifest itself through its common symptoms, which include nausea, red eyes, rashes, stomach pain, bleeding from the eyes and bruises, diarrhea, and fever.

Symptoms tend to appear 2 to 21 days after exposure to the virus, but the median remains at 8 to 10 days. The body meets Ebola infection with specific antibodies, which can stay in the blood for at least ten years.

Source: PLOS