How Ebola moves from person to person
Ebola spreads through direct contact with infected bodily fluids or tissue. The virus can be transmitted when an infected person’s vomit, blood or other fluids contact another person’s mouth, eyes or openings in their skin, said Dr. Ameesh Mehta, an infectious disease doctor at Emory University.
Even after a person has died, the virus persists. In West Africa where funeral rites include washing, touching and kissing corpses by family members, putting the dead to rest can be just as deadly as caring for a living patient.
“Contact with any aspect of it is considered very dangerous,” Cummings said. “Any physical contact.”
Ebola’s sucker punch is its speed of replication. At the time of death, a patient can have 1 billion copies of the virus in one cubic centimeter of blood. In comparison, HIV, a similar virus, has the same rate at the time of death. But unlike HIV, which only infects two types of immune cells, Ebola first infects white blood cells that disable the body’s ability to destroy foreign substances, then seizes nearly every cell type.
“It’s a systemic viral infection throughout your body as opposed to an infection of just your immune system,” Saphire said. “Patients may die before they’re able to mount much of an immune response.”
This process takes anywhere from two to 21 days (though it’s typically between four to 10 days). When the immune system begins breaking down, the symptoms begin to show.
Patients experience fevers, headaches and fatigue early on. After the virus overwhelms healthy cells, they burst, causing a chemical release leading to inflammation. Their remains are taken over by other cells, perpetuating the virus. As the symptoms worsen, patients suffer from bloody diarrhea, severe sore throat, jaundice, vomiting or loss of appetite.
Infected cells that haven’t yet burst carry the virus through the bloodstream to invade different parts of the body like the lymph nodes, spleen and liver. When infected cells attach themselves to the inside of blood vessels, it weakens them, causing fluids to leak. This triggers the uncontrollable bleeding for which Ebola is known, though it only happens for about 50 percent of patients and occurs mostly inside the body.
In fatal cases, blood pressure plummets after blood vessel damage, and death from shock or multiple organ failure occurs within six to 16 days.
The path ahead
Saphire is part of a large, multi-site team made up of 25 laboratories that’s mapping Ebola’s glycoprotein to better understand and defeat the virus. Among the potential strategies they’re studying is an antibody cocktail called ZMapp, an experimental drug that drew media attention after its use on two U.S. aid workers and three Liberian doctors. First developed by the U.S. Army Medical Research Institute for Infectious Diseases a decade ago, this “Ebola serum” potentially works to neutralize the virus by preventing its rearrangement and flagging it for destruction by the immune system.
Clinical trials for ZMapp are set to begin in 2015, but according to Saphire, doses for “experimental compassionate therapy,” treatment provided to critically-ill patients before the drug has been approved, could be ready in three months.
“The central dogma of molecular biology is that sequence dictates fold, which dictates function,” Saphire said. “But Ebola does more with less. While the human genome has 20,000 kinds of genes, Ebola has seven, and by rearranging its protein structure, it can carry out far more than seven functions.”