On Tuesday, the government of the Democratic Republic of the Congo informed the WHO of an Ebola outbreak in and around the northwestern town of Bikoro. Laboratory diagnostic tests performed by the National Biomedical Research Institute (INRB) in the capital of Kinshasa confirmed the presence of Ebola virus in two out of five samples from five different patients. An additional 21 cases of suspected viral hemorrhagic fever, including 17 deaths, have been recorded in the region. Today, Director of WHO Health Emergencies Programme Peter Salama reported that the total count has risen to 32 suspected, probable, and confirmed cases. The outbreak marks the second Ebola outbreak in the DRC in under a year and the DRC’s ninth Ebola outbreak since the discovery of the Ebola virus in 1976 along the Ebola river.

A key question at this point is whether the current outbreak will follow a similar pattern as the Ebola outbreak in DRC which was announced one year ago, on May 8, 2017. As we previously reported, that outbreak, which was declared over in July, ultimately infected eight people and killed four. The remote location of the 2017 outbreak and its relatively early detection and response by international partners are believed to have contributed to its swift containment and minimal loss of life. Below we explore the similarities and differences between the 2017 and 2018 outbreaks in terms of their geographic location, environmental risk factors, detection, and response, which can be used to inform public health interventions.

Geographic Location

The outbreak in Bikoro follows the geographic pattern of other Ebola outbreaks in the DRC, which typically emerge in remote, rural locations adjacent to heavily forested regions, allowing for the possibility of zoonosis. Bikoro, which is situated along Lake Tumba in the northwestern Equateur Province, is located over 1000 miles (1800 kilometers) from the major metropolitan area of Kinshasa. This is the third time Ebola has emerged in Equateur Province – it did so previously in 1977 and 2014.

Similarly, the 2017 Ebola outbreak in the DRC was characterized by its remote location in the Bas-Uele Province, the northernmost province of DRC located about 400 miles (640 kilometers) from the nearest major city of Kisangani. This hard-to-reach setting – with few roads and far removed from densely populated cities – likely minimized the impact and spread of the virus, which is easily transmitted from person to person by direct and indirect contact, according to the WHO.

However, a key difference between the settings from the 2017 and 2018 outbreaks is that Bikoro is situated near the border of neighboring Congo and only miles away from the banks of the Congo River, a major waterway used for travel and trade to Kinshasa as well as Brazzaville, the capital of Congo, and Bangui, the capital of the Central African Republic. The Congo river straddles the border between DRC and Congo, and friends and family routinely cross to see each other with limited border control. Without proper border screening, cross-border migration could introduce the virus to neighboring cities and countries and launch a wider pandemic. The WHO has stated it is working with the DRC government to develop a system to control the movement of boats on the river and screen for Ebola victims.

Detection

The 2017 Ebola outbreak in the DRC benefited from the swift detection of cases and rapid response activities by international and local partners. Only two and a half weeks passed since the first reports of cases (April 22, 2017) and subsequent notification of WHO of an outbreak (May 9, 2017), followed by laboratory confirmation of Ebola at the INRB in Kinshasa (May 11, 2017) This quick detection may be due to the country’s extensive experience in tackling Ebola and high clinical suspicion for Ebola among healthcare workers.

With the current outbreak, by contrast, Tuesday's press release from WHO stated that “in the past five weeks, there have been 21 suspected viral hemorrhagic fever,” but recent reports suggest that the first cases were active as early as December — with the first reported deaths in January. If true, this five-month gap between the presence of initial cases and declaration of an outbreak is significant, representing an even longer time-frame than the nearly three months it took health officials to identify the Ebola virus in Guinea during the 2014-16 Ebola outbreak in West Africa. This long time-frame — possibly the result of failures to detect and/or confirm Ebola cases — may help to explain why there have been up to 32 confirmed, probable, and suspected cases in and around Bikoro, indicating the potential for a larger outbreak than last year.

On the other hand, as journalist Helen Branswell notes, it is still “too early to assume this outbreak is this big,” since early suspected case reports are frequently unreliable. It’s possible that many of these cases of suspected viral hemorrhagic fever could turn out to be something other than Ebola, such as severe cases of malaria. Similarly, overcounting in early reports from the 2017 outbreak led to the number of suspected cases of infection being larger than the number of Ebola cases ultimately confirmed.

Response

What has seemingly remained consistent across both this year’s and last year’s outbreak is the swift pace of international action since the official outbreak declaration. As with last year, the WHO Health Emergencies Programme is working closely with the DRC government to scale up coordination and response activities, including setting up an Incident Management System. The African Union has activated its Emergency Operations Centers in the country. The WHO Contingency Fund for Emergencies is releasing $1 million in emergency funds to the DRC, while the AU is contributing an additional $250,000 for outbreak response activities. International NGOs, such as Médecins Sans Frontières (MSF), are mobilizing to the region. Kenya and Nigeria are both on high alert and have instituted screening for travelers at international airports.

A key difference in international capacities this year is the potential deployment of an experimental Ebola vaccine. The vaccine, VSV-ZEBOV, developed by Merck, has been shown during a ring trial in West Africa to offer high levels of protection, but it has never been deployed during an active outbreak and is not technically approved by any regulatory authority. Although public health officials contemplated its use during the 2017 outbreak, the swift containment of the outbreak and logistical challenges associated with transporting and storing the vaccine to remote regions meant that it was never operationalized in the field. Depending on the scale of the outbreak, VSV-ZEBOV or a similar vaccine developed by Russia and China could be administered to healthcare workers or other high-risk individuals to prevent future cases.

Additionally, laboratory testing has confirmed the virus belongs to the Zaire serotype – the most common serotype and that responsible for last year’s outbreak in DRC as well as the 2014 outbreak in West Africa – suggesting the vaccine should be effective. The Zaire variant has a case fatality in the range of 60%-90%.

Environmental Risk Factors

The cause of the latest Ebola outbreak is unknown, and no information has been released about case demographics. However, as a zoonotic disease, Ebola can jump to humans who come into contact with infected mammals, typically bats or primates, or who consume infected bushmeat.

An epidemiological study reveals that the 2007 Ebola outbreak in DRC, which led to 260 cases and 186 deaths, may have been the result of villagers hunting infected fruit bats following a massive annual fruit bat migration. Bats in particular are known to be able to travel long distances while infected with Ebola. However, the live virus has never been isolated in a bat, and the mechanism by which the virus jumps from mammals to humans is unknown. Once the virus infects the first person, human transmission usually occurs during the process of treating or caretaking for symptomatic patients or during burial rites.

Of note, deforestation is rampant in Equateur Province – the result of logging, slash-and-burn agriculture, and poverty conditions – leading to the destruction of animal habitats and likely contributing to the displacement and subsequent migration of fruit bats and other mammals closer to human settlements.

Conclusion

With the announcement of DRC’s ninth Ebola outbreak since 1976, public health officials will need to begin aggressively isolating and treating patients, contact tracing in and around Bikoro, and implementing border screenings and other interventions. While information is sparse, it is expected that more data will surface in the weeks ahead as international experts from WHO and MSF travel to Equateur Province to investigate.

Early signs point to several similarities between this and the Ebola outbreak that occurred almost a year ago in DRC in the Bas-Uele Province. These include a remote geographic location and a high level of speed and coordination among international and local response partners. Public health investigators should also consider key differences. These include the potential for the virus to spread to neighboring countries via the Congo River, as well as the longer detection time that could allow the virus to potentially infect additional cases across further distances. The availability of a new Ebola vaccine also provides officials with a potentially important tool to prevent future cases and hopefully contain the outbreak as quickly possible.

Photo: United Nations staff collaborate with national health officials during the 2014 Ebola outbreak in Equateur Province, Democratic Republic of the Congo.

Photo courtesy of MONUSCO/Jesus Nzambi from Flickr.

Outbreak Observatory aims to collect information on challenges and solutions associated with outbreak response and share it broadly in near-real time to allow others to learn from these experiences in order to improve global outbreak response capabilities