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The United States Centres for Disease Control and Prevention (CDC) announced on Thursday that it has found Marburg virus, a deadly virus similar to the Ebola virus, in fruit bats in Sierra Leone. Although there have been no reported cases of people sick with the virus in Sierra Leone, its presence in bats means people nearby could be at risk for contracting it.

According to a statement released by the US health protection agency, Marburg virus is similar to Ebola virus, causing similar and often fatal disease in people.

The scientists said the Egyptian rousette bat (Rousettus aegyptiacus) is the natural reservoir for Marburg virus. This means they can carry the virus for a long time without getting sick themselves. Infected Egyptian rousette bats may shed Marburg virus in their saliva, urine and faeces as they feed on fruits. Contaminated fruits may then be eaten by people or other animals, raising the possibility of spreading the virus. People might also be exposed to the virus through bat bites or when they capture bats to eat. Egyptian fruit bats live in caves or underground mines throughout much of Africa. 

The Marburg virus discovery came through projects funded by the United States Agency for International Development (USAID). One of the projects was led by CDC and Njala University in Sierra Leone. The other was by the University of California, Davis, and University of Makeni, also in Sierra Leone.

“This discovery is an excellent example of how our work can identify a threat and help us warn people of the risk before they get sick,” said Jonathan Towner, an ecologist at CDC who led the research team. Marburg virus has been detected in Egyptian rousette bats in Uganda, DR Congo, Gabon, Kenya and South Africa. It is the first time the deadly virus has been found in West Africa.

“That the discovery was made in bats before the recognition of any known human illnesses or deaths is exactly what PREDICT’s One Health approach to disease surveillance and capacity building are designed to do,” said Brian Bird, a virologist with the University of California, Davis, and Global Lead for Sierra Leone and Multi-Country Ebola operation for PREDICT-USAID.

In 2009, the USAID initiated the PREDICT project as part of its Emerging Pandemic Threats (EPT) programme to strengthen global capacity for detection and discovery of viruses with pandemic potential that can move between animals and people. Currently, about 24 countries in Africa, Latin America and Asia are engaged in the programme.

According to the statement, there have been 12 known Marburg virus outbreaks with direct links to Africa. The most recent outbreak happened in Uganda in 2017, while the largest and deadliest outbreak occurred in Angola in 2005. It killed 90 per cent (or 227 people) of the 252 people who were infected.

The CDC/Njala and UC Davis/University of Makeni projects began in 2016 following the massive Ebola outbreak in West Africa. The projects sought to discover Ebola reservoir – animals that help maintain the virus in nature by spreading it without getting sick.

The outbreak of Ebola disease in West Africa began in Guinea in December 2013, and spread to Sierra Leone and Liberia. Over 11,000 people died from the disease, making it the worst Ebola epidemic in history. As a result of poor medical facilities, the fatality rates went up to 70 percent. Liberia recorded the highest fatalities at 4,808 deaths, while about 3,955 people died in Sierra Leone. In November 2015, Sierra Leone declared the end of Ebola disease transmission.