Sacra, 51, was practicing at the same hospital where the other two infected Americans, Nancy Writebol and Dr. Kent Brantley, worked. Though he was not treating Ebola patients, Writebol said the hospital did not have sufficient resources to protect workers.
According to SIM USA, Sacra was quarantined after his temperature began to rise but was still well enough to be sending emails on Wednesday.
Writebol and Brantley are recovering after receiving the experimental drug ZMapp.
"We don't have enough personal protective safety equipment to adequately be able to safely diagnose if a patient has Ebola," said David Writebol, Nancy's husband.
The U.S. Agency for International Development (USAID) has been airlifting emergency medical supplies, including chlorine and gloves, reports the BBC.
"The window of opportunity to stop Ebola from spreading widely throughout Africa and becoming a global threat for years to come is closing, but it is not yet closed," said Dr. Tom Frieden, who recently returned from West Africa. "If the world takes the immediate steps -- which are direct requests from the front lines of the outbreak and the presidents of each country -- we can still turn this around."
More than 1,900 people have died from Ebola and at least 3,500 have been infected. The World Health Organization (WHO) reports the outbreak has about a 50 percent fatality rate.