An American doctor working in the Democratic Republic of Congo (DRC) has tested positive for Ebola and is now being treated in Germany.

Dr. Peter Stafford, a general surgeon with Serge, an international Christian mission, is receiving care at Berlin's Charite University Hospital, according to Serge. His wife, Dr. Rebekah Stafford, and their four children, as well as another physician, Dr. Patrick LaRochelle, have also left DRC for Europe where they will be monitored. Stafford's wife and LaRochelle both may have been exposed through their work in hospitals in the region, and the Staffords' children through close contact with their parents. The U.S. Centers for Disease Control and Prevention (CDC) said only Stafford exhibited symptoms of Ebola. In a statement, Serge said Stafford developed symptoms after treating patients in the Ituri province in eastern DRC before the outbreak was declared.

During the outbreak so far in DRC and Uganda, more than 600 suspected cases are being tracked and officials believe as many as 139 people may have died from Ebola, said Dr. Tedros Ghebreyesus, director general of the World Health Organization (WHO) at a briefing on May 20. Violence and political unrest in the region, as well as poor health care infrastructure and lack of proper protective equipment for health care workers, means the virus is spreading quickly, says Dr. Alan Gonzalez, deputy director of operations at Doctors Without Borders/Médecins Sans Frontières, which already had teams in the area providing a range of health services, from pediatric care to malaria treatments. On May 17, Ghebreyesus declared the Ebola outbreak in DRC and Uganda to be a public health emergency of international concern, a designation that activates additional global resources, personnel, and funding to address the public health threat.

Captain Satish Pillai, incident manager for CDC’s Ebola response said the CDC is working closely with health officials in DRC and Uganda to support them in containing the outbreak, including by providing technical experts on Ebola both in person and remotely. On May 19, the U.S. government advised Americans not to travel to the DRC, Uganda, or south Sudan. The State Department is also restricting entry into the U.S. of any foreign nationals who have been in those three countries over the past 21 days, which is the incubation period of the Ebola virus.

Ebola outbreaks have been common in the DRC since the mid 1970s, when the virus was first identified, and the region has reported at least 16 outbreaks prior to this one in that time. But most have involved the Zaire strain, which has a high fatality rate ranging from 60% to 90% and causes fever, muscle aches, headache, and ultimately internal bleeding and organ failure.

The latest outbreak began with reports to WHO in early May of unexplained deaths, including among health care workers, in Ituri Province in DRC. In just over a week, lab tests confirmed the Bundibugyo strain of Ebola, which has a lower mortality rate of 30% to 50% than Zaire but still causes similarly serious and sometimes fatal disease. Because Zaire has been more common, several antiviral and monoclonal antibody therapies are available to treat it, but none currently target Bundibugyo, making control of the latest infections more challenging. Health workers say the lack of test for Bundibugyo may have delayed the reporting of cases and allowed it to spread. "This is only the third time this Bundibugyo strain is causing an outbreak in recorded history," says Gonzalez. "So the vaccines that were developed before, the specific therapeutics that were developed before, and the testing capacity we developed before for Zaire don't work for this strain."

Ebola spreads through direct contact with infected body fluids, and health officials believe the virus spreads to people from infected bats or primates. Health care workers in parts of Africa are especially vulnerable since they often don’t have the proper personal protective equipment when caring for patients and aren’t always aware patients may be infected, since the initial symptoms are indistinguishable from other infections.

Since January, drastic cuts in funding—especially to programs like USAID, which has played a large role in supporting international efforts to address public health threats—have also impacted health care in the region. Pillai said the CDC has 25 people in the office the agency maintains in DRC, and that number “hasn’t substantially changed. Anything the country office and the ministry [of health] are requesting for support, we will be providing remotely as well as in the field,” he said.

Because there are no specific treatments for Bundibugyo, health officials are focusing on testing, contact tracing to identify people who might have been exposed, and isolation strategies to control the infection. Addressing other infections people may have and ensuring they have proper hydration are also important. Such approaches are critical to containing the outbreak, says Gonzalez, even in the absence of treatments. "We've seen in the last outbreaks that this has a massive impact on the outcomes for patients, even without specific therapeutics," he says.

So far, there are no cases of Ebola reported in the U.S. “The risk to the U.S. remains low,” Pillai said.