Diagnosing Ebola disease shortly after infection can be difficult. Early symptoms of Ebola disease such as fever, headache, and weakness are not specific to infection with ebolaviruses and often are seen in patients with other more common diseases, like malaria and typhoid fever.
To determine whether Ebola disease is a possible diagnosis, there must be a combination of symptoms suggestive of Ebola disease AND a possible exposure to an ebolavirus within 21 days before the onset of symptoms. An exposure may include contact with:
- blood or body fluids from a person sick with or who died from Ebola disease,
- objects contaminated with blood or body fluids of a person sick with or who died from Ebola disease,
- infected fruit bats and nonhuman primates (apes or monkeys), or
- semen from a man who has recovered from Ebola disease.
If a person shows signs of Ebola disease and has had a possible exposure, he or she should be isolated (separated from other people) and public health authorities notified. Blood samples from the patient should be collected and tested to confirm infection. Ebolaviruses can be detected in blood after onset of symptoms. It may take up to three days after symptoms start for the virus to reach detectable levels.
Polymerase chain reaction (PCR) is a commonly used diagnostic method for Ebola disease because of its ability to detect low levels of an ebolavirus. PCR methods can detect the presence of a few virus particles in small amounts of blood, but the ability to detect the virus increases as the amount of virus increases during an active infection. When the virus is no longer present in great enough numbers in a patient’s blood, PCR methods will no longer be effective. The detection of antibodies is another method used to confirm a person’s exposure to and infection by an ebolavirus.
A positive laboratory test means that an ebolavirus infection is confirmed. Public health authorities will conduct a public health investigation, including identifying and monitoring all potentially exposed contacts.