Ebola is caused by a group of viruses that are part of the Orthoebolavirus family. They were discovered in 1976 in what is now Congo. In addition to the Ebola virus, which causes Ebola virus disease, there are also the Sudan virus, Bundibugyo virus and Taï Forest virus that can cause severe illness in humans.

This new outbreak in Congo is caused by Ebola virus. It is the 16th Ebola disease outbreak reported there since 1976.

 What are the symptoms of Ebola, and how soon do they start after exposure?

Wen: The incubation period for Ebola disease is two to 21 days, but the average time between exposure and symptoms is eight to 10 days. Initially, the patient exhibits “dry” symptoms, such as fever, joint and muscle headaches, severe headache, and fatigue. These are nonspecific symptoms that often lead to misdiagnosis with other illnesses such as influenza, malaria or typhoid fever.

Four to five days after symptom onset, patients can progress to “wet” symptoms that are characteristic of Ebola infection. Specifically, individuals may develop gastrointestinal symptoms such as abdominal pain, vomiting and diarrhea; rash; chest pain; as well as bleeding from the eyes, mouth, nose and rectum. The disease may progress to organ failure, seizures, brain inflammation and death.

How is Ebola spread?

Wen: The primary way is person to person. Someone can be infected if they come in contact with blood or body fluids from an individual who is sick or has died of Ebola. Objects contaminated with an infected person’s fluids can also spread the disease. These items include bedding, utensils, clothes and medical equipment.

Transmission has also been reported through sexual contact, specifically through semen of those who are infected with or have recently recovered from Ebola disease. In addition, humans can contract Ebola from hunting, handling or eating infected animals such as bats, monkeys and antelope.

How are Ebola patients treated?

Wen: Patients with Ebola disease are immediately isolated to prevent transmission to others. Supportive care is essential and includes giving fluids and electrolytes to replace those lost through illness. If blood pressure or oxygen levels fall, intensive care is required to stabilize circulation and breathing. Patients may also need treatment for secondary infections or for complications related to preexisting conditions.

Two treatments are currently approved by the US Food and Drug Administration to treat Ebola virus disease: a combination of three monoclonal antibodies, and a single monoclonal antibody. In clinical trials, these therapies were shown to reduce mortality, although the death rate remains high even with treatment. Because these medicines are costly and logistically challenging to deliver, access to them is limited, particularly for patients in sub-Saharan Africa, where most Ebola outbreaks occur.

Is there a vaccine?

Wen: Yes. The FDA approved a vaccine, Ervebo, against Ebola virus disease in 2019. A second vaccine is authorized in Europe but not available in the United States.

Ervebo is designed for use during outbreaks as part of a strategy called “ring vaccination.” This approach involves vaccinating people at the highest risk of infection, such as those in close contact with confirmed Ebola patients, the contacts of those contacts, and frontline health care workers. By creating a “ring” of protection around cases, the goal is to contain the spread of the virus.

The FDA has approved one vaccine, Ervebo, against Ebola virus disease.

According to WHO, an initial 400 doses of Ervebo have already been deployed to one of the outbreak hotspots in Congo; additional doses are being delivered in the coming days.

What else should people know about the outbreak? Why is the CDC issuing alerts?

Wen: While Ebola is a deadly disease and it is crucial that public health resources be deployed to help Congo, this outbreak has not affected the US so far. As the CDC says, no suspected, probable or confirmed Ebola virus disease cases related to the current outbreak have been reported in the US or outside Congo. At this time, the risk of spread to the US is low.

The CDC’s notice for travelers to Congo recommends avoiding contact with ill individuals during travel and monitoring for symptoms until 21 days after leaving the area. People who develop symptoms must immediately isolate themselves and call their doctor or local health department.

Issuing a health advisory alerts clinicians to consider Ebola in patients who have concerning symptoms and who have recently traveled to infected areas. The advisory also provides resources for hospitals, laboratories and public health departments that may be involved in treating patients, handling and testing specimens, or responding to community questions about Ebola.

Are there other recommendations for the public now?

Wen: There are no special recommendations for the general public outside the regions where Ebola virus is present. For people living in or visiting affected areas, however, taking precautions is essential. Avoid contact not only with people who are ill but also with anything that may be contaminated by their body fluids. In addition, do not visit any health care facilities unless you have an urgent medical need.

Traditional burial practices that involve touching the body of the deceased should be avoided. Also avoid bats, monkeys and forest antelope, and do not enter caves or mines where bats may live. Finally, anyone who develops symptoms should isolate immediately and seek medical care.