Q&A: Ebola outbreak and public health emergency

UNIVERSITY PARK, Pa. — This week, the World Health Organization declared an international public health emergency due to an outbreak of Ebola in the Democratic Republic of the Congo. The outbreak, which has already killed more than 100 people, took longer to identify as the virus species is different than the species typically responsible for Ebola outbreaks. There is no vaccine for this species of Ebolavirus, but researchers are testing the effectiveness of a vaccine for a different species of the virus, according to Ebola expert Nita Bharti, associate professor of biology and Lloyd Huck Early Career Professor at Penn State.

In this Q&A, Bharti and Kelsee Baranowski, a postdoctoral researcher in Bharti’s lab at the Center for Infectious Disease Dynamics, discussed what Ebola is, how it affects people and how this outbreak matters to people in the United States and across the world. Bharti also discussed Ebola in this video.

Q: What is Ebolavirus?

Bharti: Ebola refers to a genus of viruses. Three species in this genus have caused almost all the human cases you’ve ever heard about: Zaire, Sudan and Bundibugyo, which is causing the current outbreak.

Baranowski: Ebola viruses circulate in a reservoir host population. A reservoir host is a host that naturally harbors the pathogen without experiencing disease or sickness. The reservoir hosts of Ebola viruses are thought to be fruit bats. Reservoir hosts can transmit Ebola viruses to species that experience disease, like humans, other primates, and some antelopes.

These cross-species transmission events are called “spillovers” and they’re relatively rare. However, the frequency of Ebola virus outbreaks in humans has been increasing since the first documented occurrence in 1976. Ebola spillovers and human outbreaks have occurred primarily across Central Africa with some incidents in West Africa.

Q: How and where do people become infected with Ebola?

Baranowski: Humans can become infected through contact with infected bats or other spillover species. Once Ebola infects a human, the virus can spread directly from a symptomatic person to a susceptible person. In the absence of interventions, one sick person will, on average, infect between one and two other people.

Bharti: Ebola is transmitted by direct contact through bodily fluids like blood or vomit of an infected, symptomatic person. It is not casually transmitted by handshakes or respiratory droplets when coughing or sneezing, like influenza can be. Caregivers are the most likely to be infected, including health care workers and family members. The remains of deceased patients are also highly infectious.

Q: What happens to people who contract Ebola?

Baranowski: The three Ebola virus species mentioned above — Zaire, Sudan and Bundibugyo — have high fatality rates in spillover hosts. Between 50% and 90% of people infected with Ebola will die if they do not receive medical care, depending on which species of the infection they have.

Bundibugyo — the species of the current outbreak — has only caused two previous outbreaks, and both were located near the current outbreak. The case fatality rate is estimated around 50%, which is lower than Zaire but still very high.

The current outbreak is centered in the Democratic Republic of the Congo (DRC), which has experienced 16 prior Ebola outbreaks. The rarity of the Bundibugyo virus understandably caused some delays in early detection of this outbreak.

The Zaire species of the virus has caused the most human outbreaks as well as the most human cases and deaths. It was responsible for the largest human Ebola outbreak: the devastating West African outbreak from 2013-16, which caused over 28,000 human cases and 11,000 deaths. There is now a safe and effective vaccine against the Zaire species.

Bharti: That outbreak and other outbreaks since showed us that Ebola infections in dense populations or urban areas can transmit quickly and become difficult to manage.

Q: Can the vaccine help in the current outbreak? What else is being done?

Bharti: There is some cross immunity between the Zaire, Sudan and Bundibugyo species. Work is currently being done to assess whether the Zaire vaccine could provide any protection against the currently circulating Bundibugyo virus, but it is not expected to be as effective against this off-target species.

The current response to this outbreak is focused on testing, contact tracing and isolating people with infections to reduce transmission and minimize the spread of the outbreak to new areas. There is a lot of population mobility in the affected area, so contact tracing has posed a significant challenge. Identifying all the chains of transmission and containing the outbreak is critical.

Baranowski: Specifically, contact tracing identifies people who could have been exposed to the virus through contact with an infected individual. Contacts of cases are tested and observed. Infected individuals are isolated and treated. While there is no specific treatment for this species of Ebolavirus, basic patient care and support improve survival rates.

During prior Ebola outbreaks, funerals were retrospectively identified as superspreader events. Safe and dignified burials are also a cornerstone of outbreak management to reduce Ebola transmission.

Q: What is likely to happen as the outbreak continues?

Baranowski: Outbreak management efforts have identified cases that are not linked to each other. This indicates that the virus is moving along multiple branches of transmission, and they are not all detected. The actual number of cases is likely much larger than the current numbers show. The confirmation of cases in densely populated areas is also concerning.

Bharti: This outbreak is occurring in an area where health systems are not strong due to ongoing conflict, displacement, and human mobility. This is not surprising. These are the factors that allow health crises to emerge, delay diagnostics, and complicate contact tracing and outbreak management.

Q: Who should be concerned?

Baranowski: Anyone who provides care for Ebola patients must be extremely cautious. Anyone who is at risk of coming into close contact with a symptomatic Ebola patient should take serious precautions by using personal protective equipment like masks and gloves. People in the immediate vicinity of the ongoing outbreak should be aware and cautious.

Americans in areas of DRC and Uganda where cases have been identified should be aware of the situation and assess their level of risk of coming into close contact with Ebola patients. Americans in the United States are not at risk of becoming infected.

Bharti: The DRC has experienced more outbreaks of Ebola than any other nation. Local medical and research expertise on these viruses are unparalleled. Outbreak response is being managed by local experts with support from global health organizations.