People get the disease by direct contact with virus-infected blood, body fluids, organs, or semen.

The disease is spread mainly by close person-to-person contact with severely ill patients. This happens most often to hospital-care workers and family members who care for an ill person infected with Ebola virus. Close personal contact with persons who are infected but show no signs of active disease is very unlikely to result in infection.

Transmission of the virus has also been linked to the re-use of hypodermic needles in the treatment of patients. Re-using needles is a common practice in developing countries, such as Zaire and Sudan, where the health-care system is underfinanced. Medical facilities in the United States do not re-use needles.

Ebola virus can be spread from person to person through sexual contact. Persons who have recuperated from an illness caused by Ebola virus can still have the virus in their genital secretions for a short time after recovery and can spread the virus through sexual activity.