Washington, Sep 3 (IANS) An American missionary doctor working in Liberia has tested positive for the Ebola virus, his organisation SIM USA announced Tuesday.

The doctor was treating obstetrics patients at ELWA hospital in Liberia's capital Monrovia and was not treating Ebola patients in the hospital's Ebola isolation unit, a facility separate from the main hospital, Xinhua quoted the missionary organisation's statement as saying.

It is not yet known how the doctor contracted the virus specifically.

"Upon onset of the symptoms, the doctor immediately isolated himself and has since been transferred to the ELWA Ebola isolation unit," SIM USA said.

"The doctor is doing well and is in good spirits."

The news came about two weeks after Nancy Writebol, who also worked for SIM USA, and her colleague Kent Brantly, were released from a hospital in Atlanta.

The two contracted the Ebola virus in July while treating patients in Liberia and were later evacuated to the US for treatment.

According to the World Health Organisation (WHO), the deadly virus for which there is no treatment or vaccine, has claimed 1,552 lives out of 3,069 reported cases, including 694 in Liberia, 430 in Guinea, 422 in Sierra Leone and six in Nigeria.