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Ebola wasn’t known about until 1976. In that year it suddenly caused separate outbreaks in the now Democratic Republic of the Congo and South Sudan. It’s a virus that remains most of the time in bats, largely in Central and Western Africa, but every once in a while, it spreads to humans. It can spread from contact with a bat or from hunting or picking up another animal that’s sick or dead from Ebola.

Ebola is something we consider important to control because it can kill about half of those infected and can close down many hospitals and clinics, resulting in others not being able to get care.

The virus spreads by direct contact with blood or other body fluids (such as vomit, diarrhea, urine, breast milk, sweat, and semen) as well as bedsheets or clothing contaminated by the body fluids of an infected person. The virus often spreads in hospitals when people who are sick seek care, especially women in labor as it can cause more bleeding in labor.

Ebola develops 2 to 21 days after exposure (usually 8 to 10 days). Ebola doesn’t spread before symptoms. There are usually two stages of Ebola:

 Dry stage: The first stage is the dry stage, characterized by fever, aches and pains, sore throat, and fatigue. This stage can be mistaken for influenza or the flu. Some people also have hiccups, which can help identify the illness as Ebola because hiccups and fever are not that common.

 Wet stage: The disease then progresses to the wet stage (with more fevers and now diarrhea and vomiting and sometimes bleeding and miscarriage in pregnant women). It is in the wet stage that people are very sick and often become confused. They need the help of others to take care of them, and they are also the most infectious then. Ebola can spread from the diarrhea, sweat, and other body fluids, making others sick. The virus often infects family members who care for those who are sick, nurses and doctors, and those involved in preparing for funerals as bodies after death remain infectious.

Some people have very mild cases, and others have very serious cases. The initial amount of virus someone has in their blood when tested can predict their chance of getting better. People who get better from Ebola can go back to their regular lives and aren’t infectious once they clear the virus. However, the virus can hide where the immune system doesn’t notice the virus as quickly. For example, the virus can remain in men’s testes and result in spreading the virus through sex, even a year later. Some people also can have eye symptoms and vision loss later on because the virus can remain in the eye and cause inflammation.

Most outbreaks have been fewer than 100 cases. It wasn’t until Ebola was identified in West Africa in 2014, as it spread largely between Liberia, Sierra Leone, and Guinea, that we ever saw a large epidemic over a few hundred. This outbreak spread unnoticed at first but then rapidly caused over 28,000 cases and over 11,000 deaths. A large international commitment of people working in collaboration was required to control it, as the virus often spreads among clinics and hospitals, affecting those most needed to fight it and making it even harder to contain.

Ebola is called a viral hemorrhagic fever (VHF). That means it is a virus that causes a fever, which can be accompanied by bleeding, often with a severe infection affecting multiple organs. There’s often a lot of fear around the bleeding, but in reality bleeding is not that common and usually not the worrisome part of the disease. Instead, it’s that the virus can affect multiple organs, making it difficult for them to function together.

We’re on the lookout for other related and unrelated viruses that also cause VHFs. These include Lassa (a close relative to Ebola), yellow fever, dengue (rarely causes a VHF), Crimean-Congo hemorrhagic fever, Rift Valley fever, and about ten others. We never want to have a case of a viral hemorrhagic fever, but although these viruses can seem scary, if the correct actions are taken to stop transmission and control the outbreak, they can be stopped.