 By using ELISA to measure Zaire Ebola virus antibody concentrations, we identified a significant number of individuals with previously undetected EBOV infection in a ‘hotspot’ village in Sierra Leone, approximately one year after the village outbreak. "The findings provide further evidence that Ebola, like many other viral infections, presents with a spectrum of clinical manifestations, including minimally symptomatic infection," the researchers write. "These data also suggest that a significant portion of Ebola transmission events may have gone undetected during the outbreak." From October 2015 through January 2016, a year after the peak of the Ebola epidemic, Eugene Richardson, of Partners In Health, and colleagues conducted a survey of people living in Sukudu, Kono District, Sierra Leone, a village of 900 inhabitants which had been a major "hotspot" of Ebola. They then tested the blood samples -- as well as positive and negative controls from known Ebola cases and people not exposed to the virus -- for Ebola glycoprotein antibodies, the presence of which indicates a past Ebola infection. Researchers reporting in PLOS Neglected Tropical Diseases have discovered individuals in Sierra Leone who showed no signs of the disease but have evidence of prior Ebola infection in their immune systems. Two of the 14 seropositive individuals reported only fever during quarantine while the remaining 12 denied any signs or symptoms during quarantine. However, researchers have also seen some evidence that a minority of people may catch the Ebola virus without developing symptoms. During the 2013-2016 outbreak, however, these so-called "minimally symptomatic infections" were not considered epidemiologically relevant to models, projections, or intervention efforts so were not studied or tracked in detail. In order to improve our understanding of the transmission dynamics of EBOV in humans, we investigated the occurrence of minimally symptomatic EBOV infection in quarantined contacts of reported Ebola virus disease cases in a recognized ‘hotspot.’ 
 
 With over 28,000 reported cases, the 2013–16 West African Ebola virus disease epidemic is the largest and longest on record. In other words, they have “minimally symptomatic infections.” 
 
 Prior to the new study, scientists suspected that Ebola, like many other viruses, might not always manifest in the same predictable way. The finding suggests the recent West African Ebola Epidemic was more widespread than previously thought, and that new methods need to be developed to diagnose and contain the dreaded virus during an outbreak. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Working with a local physician, Richardson’s team tested 187 men, women, and children from Sukudu who had likely been exposed to Ebola, either because they lived in the same household or shared a public toilet with a person known to have had the disease. Specifically, these included fever or unexplained bleeding or any three of the following: headache, myalgia, rash, vomiting, diarrhea, hiccups, breathing problems, or difficulty swallowing [ 13 ]. The team identified 193 adults and children over age 4 who had lived with or shared a latrine with a confirmed case of Ebola during the period of active transmission but were never identified as EVD cases. Subjects received 50,000 Leones (~$10 US) for their participation in the study. Discussion 
 
 One year after the peak of the Ebola epidemic in Sierra Leone, we identified positive IgG responses to Zaire-EBOV in 14 individuals not known to have had EBOV infection from a village classified as a hotspot for Ebola transmission. A dozen of these villagers said they had no symptoms of the disease, while two recalled having a fever at the time of the outbreak. In another study in Gabon, Becquart and colleagues found a 15.3% Ebola Zaire IgG seroprevalence in 220 randomly selected villages and concluded that most of the seropositive persons identified “probably had mild or asymptomatic infection” [20]; however, they used uninfected individuals in France as negative controls.
– Ebola doesn't always show itself through fever, vomiting, and diarrhea. A new PLOS study finds that some people with the virus show mild or no symptoms at all—a potential concern for preventing its spread. Researchers who visited the village of Sukudu in Sierra Leone, a hot spot in the recent West African Ebola outbreak, found up to 25% of Ebola infections "may have been minimally symptomatic," meaning "a significant portion of Ebola transmission events may have gone undetected" in Guinea, Sierra Leone, and Liberia, NBC News reports. At least 28,000 people are known to have been infected during the epidemic, at least 11,000 of whom died. In Sukudu, there were 34 known Ebola cases, including 28 deaths among 900 residents, reports Gizmodo. A year after the worst of the outbreak was over, Stanford University researchers tested the blood of 187 people in Sukudu who'd lived with or shared a toilet with someone infected with Ebola, per a release. They found 14 had Ebola antibodies, suggesting they'd previously been infected, while 12 said they didn't recall feeling sick or having a fever. Believing them to be truthful as health workers kept an eye on villagers during the outbreak, researchers now plan to visit other villages "so we can begin to answer the question of what was the true burden of disease," the study author says. "We expect to find a lot more undocumented survivors." It's not clear if asymptomatic patients are contagious. "They were not passing it along in the usual way, through vomiting or diarrhea," he says. "It's unclear if they can pass it along sexually." (This Ebola-like disease can shut down organs.)