Ebola targets and disables key immune cells, preventing the body from mounting an effective response. Understanding its mechanisms is crucial for developing effective treatments and containment strategies.
Key points
Ebola virus targets immune cells
Disables immune response
Understanding mechanisms is crucial
Effective containment strategies needed
Mentioned in this story
Democratic Republic of Congo
Health workers carry the coffin of a person suspected of having died from Ebola in the Democratic Republic on Congo.
Health workers carry the coffin of a person suspected of having died from Ebola in the Democratic Republic on Congo.
Glody Murhabazi/AFP/via Getty Images
Glody Murhabazi/AFP/via Getty Images
Ebola is a wily pathogen.
After jumping to a new person through the bridge of bodily fluids, it goes straight for key immune cells. In typical infections, these immune cells help mount a targeted response to the virus with the goal of clearing it out. But the virus that causes Ebola somehow disables this response.
"That adaptive immune response that we hope for in terms of getting full clearance is often very strongly delayed," says John Connor, a virologist at Boston University.
That gives the virus a head start in rapidly spreading throughout the body. It goes first to the lymph nodes, then to the spleen, liver and kidneys, replicating and damaging these tissues as it goes.
"The cleaning and garbage disposal units of the body are backing up, and that backs up into the blood system, [and] that has a lot of negative consequences," says Connor.
By this point, the immune system still isn't creating antibodies that flag the invader for clearance by other cells. But the immune system has sensed that something is wrong, and spurs a more brute force reaction. In many Ebola patients, this response can go overboard, causing a frenzy of immunological activity known as a cytokine storm – named for the proteins that stoke an inflammatory response.
"That can lead to a lot of essentially collateral damage rather than focused removal of virus from infected cells," says Connor, contributing to multiple organ failure. Later symptoms include vomiting and diarrhea, which can cause patients to lose over 2.5 gallons of fluids a day. In some cases, blood vessels become so damaged they leak. Losing all this fluid is often what kills roughly half of patients who get infected.
But this high mortality rate isn't inevitable, even in the absence of approved treatments targeting the virus.
What clinicians call supportive care — replacing fluids, managing blood pressure, treating other infections — can help keep patients alive long enough for their bodies to counter Ebolavirus' stealth maneuvers. But such care is often out of reach for patients at the epicenters of Ebola outbreaks, including the one in the Democratic Republic of Congo, because of under-resourced medical facilities.
Q&A
How does Ebola virus affect the immune system?
Ebola virus targets key immune cells and disables their ability to mount a response, allowing the virus to proliferate.
What are the main symptoms of Ebola infection?
Main symptoms of Ebola infection include fever, severe headache, muscle pain, weakness, fatigue, and gastrointestinal symptoms.
What measures are effective in stopping the spread of Ebola?
Effective measures to stop the spread of Ebola include isolating infected individuals, safe burial practices, and vaccination.
Where is Ebola most commonly found?
Ebola is most commonly found in parts of Africa, particularly in the Democratic Republic of Congo and surrounding regions.
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Krutika Kuppalli still remembers her first day treating Ebola patients in Port Loko, Sierra Leone.
The infectious diseases physician, now at UT Southwestern Medical Center, arrived there in November 2014, to help care for patients during the massive Ebola outbreak in West Africa that killed over 11,000 people.
"It was really hard," she says. "I remember going in the first day, I still have the picture in my mind of these three patients slumped over the bed, and I didn't know if they were alive or not."
Her number one job was helping her patients replace lost fluids. She'd try to get patients to drink oral rehydration salts, akin to Pedialyte, if they could keep it down. "It tastes really horrible," she says. If they couldn't, an IV could replace lost fluids and electrolytes.
In the thick of an Ebola outbreak, that kind of basic care is hard to deliver, she says.
"First of all, you have to put on all the PPE to get into the treatment unit," she said. "I'm covered head to toe in a Tyvek suit, a face mask, goggles and double gloves, I can't really do much to assess a patient other than look at them."
In the tropics, overheating in PPE is a major concern, says Armand Sprecher, a physician with Doctors Without Borders. "When you sweat, it doesn't evaporate, you don't get rid of heat, it just ends up being puddles in your boots," he says. "When you get wrapped up in the PPE, the clock starts. Passing out is a real possibility, and clinicians only have about 45 minutes at a time.
During those windows, they need to see dozens of patients. Within such constraints, a health care worker can only do so much.
"People talk about 15 minutes with their doctors, not [being] enough. Imagine five minutes with your doctor if you've got Ebola," says Craig Spencer, an emergency medicine physician at Brown University who treated Ebola patients in Guinea. "That was just a reality of not having enough providers and not having the resources that we needed."
Disparities in care
Spencer experienced an entirely different reality when he returned from Guinea in 2014 with Ebola himself. After developing symptoms, he ended up at Bellevue Hospital in New York.
"In Guinea, I was taking care of 30 to 40 patients at any time. In the U.S., there were probably 30 to 40 providers on call anytime just to take care of me," he says. Those providers were in air-conditioned rooms, allowing them more time with Spencer. They could also run a whole suite of tests to precisely tailor Spencer's treatment and keep up with fluid loss, something largely unavailable where he worked in Guinea.
U.S. hospitals with Ebola patients could provide even more specialized care, like dialysis to make up for damaged kidneys, or putting patients on ventilators to help with breathing.
"It was seemingly unlimited access to anything and everything that you might need to improve your chance of survival," he says. The difference in outcomes is clear — of the 11 people ever treated for Ebola in the U.S., 9 survived. That's a dramatically higher survival rate than was seen in West Africa in 2014, where only about half of patients walked out of treatment clinics.
Since then, new Ebola vaccines and treatments have made caring for patients easier. But caring for patients now in the Democratic Republic of Congo may be similar to what happened in that 2014 outbreak, given that the vaccines and treatments developed for that strain aren't approved for the rarer Ebola species circulating now. Additionally, ongoing conflict in northeastern DRC could make dispatching clinical care teams even harder.
"The goal is to be able to provide a higher standard of care than we were providing a decade ago," says Spencer. "But I think initially it's going to be pretty blunt triage in terms of what we're capable of doing."
