Because the natural reservoir of ebolaviruses has not yet been proven, the manner in which the virus first appears in a human at the start of an outbreak is unknown. However, researchers have hypothesized that the first patient becomes infected through contact with an infected animal.
When an infection does occur in humans, the virus can be spread in several ways to others. The virus is spread through direct contact (through broken skin or mucous membranes) with
- a sick person's blood or body fluids (urine, saliva, feces, vomit, and semen)
- objects (such as needles) that have been contaminated with infected body fluids
- infected animals
Healthcare workers and the family and friends in close contact with Ebola patients are at the highest risk of getting sick because they may come in contact with infected blood or body fluids.
During outbreaks of Ebola HF, the disease can spread quickly within healthcare settings (such as a clinic or hospital). Exposure to ebolaviruses can occur in healthcare settings where hospital staff are not wearing appropriate protective equipment, such as masks, gowns, and gloves.
Proper cleaning and disposal of instruments, such as needles and syringes, is also important. If instruments are not disposable, they must be sterilized before being used again. Without adequate sterilization of the instruments, virus transmission can continue and amplify an outbreak.