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Data from DRC suggest many Ebola infections may go unrecognized
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Researchers documented serologic evidence of exposure to Ebola virus in villages that were not affected by an outbreak of the disease in the Democratic Republic of the Congo. The people were seemingly asymptomatic, suggesting that many Ebola infections may go unrecognized.
In a study conducted in 14 rural villages in 2007, 11% of people tested positive for Ebola antibodies, according to Anne W. Rimoin, PhD, MPH, associate professor in the department of epidemiology at the UCLA Fielding School of Public Health, and colleagues.
“Because the symptoms [of Ebola virus (EBOV) infection] can be nonspecific and range from flu-like symptoms to acute hemorrhagic fever, it is probable that there are many cases that go unrecognized, unreported, and attributed to other common illnesses such as malaria, typhoid or influenza,” Rimoin and colleagues wrote in The Journal of Infectious Diseases. “Our analyses suggest that individuals outside known outbreak zones in central DRC may be exposed to EBOV.”
The study was conducted from August to September 2007 while an Ebola outbreak was ongoing in two nearby health zones. In addition to testing serum, Rimoin and colleagues also assessed risk factors for Ebola exposure and found that the odds of a positive test were higher in males aged older than 15 years and were significantly associated with visits to the forest, hunting, butchering or skinning animals, and exposure to rodents and duikers, a type of antelope.
In recently published findings, Rimoin and colleagues documented that some Ebola survivors in the DRC still have antibodies against the virus 40 years after they were infected. The country has experienced eight Ebola outbreaks since the virus was first discovered near the Ebola River in 1976. The latest occurred last year in a remote area with just 12 miles of paved roads.
According to Rimoin and colleagues, most Ebola outbreaks have occurred in remote areas, where transportation and communication is difficult and disease surveillance is suboptimal. Rimoin said these outbreaks are poorly understood and that is important to know what role asymptomatic, minimally symptomatic “or just plain unrecognized” Ebola infections may play.
During the recent West African Ebola epidemic, for example, Rimoin said many individuals who were suspected of being infected never presented to a health care facility and were never diagnosed and recorded as survivors. She said patients with unrecognized but symptomatic disease who managed to avoid detection “are thought to have the same level of exposure and potential for post-infectious sequelae as diagnosed [Ebola] survivors.”
“Further studies are needed to better understand transmission dynamics, reservoir and spectrum of Ebola virus disease infection,” Rimoin told Infectious Disease News. “If history tells us anything, it’s not if another outbreak will occur, but when.” – Gerard Gallagher
References:
Mulangu S, et al. J Infect Dis. 2018;doi:10.1093/infdis/jix619.
Rimoin AW, et al. J Infect Dis. 2017;doi:10.1093/infdis/jix584.
Disclosures: The authors report no relevant financial disclosures.