Africa’s efforts to contain a widening Ebola outbreak are being tested by porous borders, illegal crossings and infected travelers who can pass through screening before developing symptoms.

The Kenyan man who became the country’s first case crossed illegally from the Democratic Republic of Congo into Uganda before flying from Entebbe to Nairobi, said Wessam Mankoula, an Africa Centres for Disease Control and Prevention epidemiologist. The Congo-Uganda border is closed to ordinary passenger traffic, though trucks and humanitarian movements are permitted.

“There are informal points where some of the people may be using for this kind of informal crossing,” Mankoula said.

Stopping cross-border spread requires “multiple layers for detection,” including surveillance within communities and health facilities and laboratory capacity to identify cases that aren’t picked up at borders, Mankoula said.

The case highlights the difficulty of containing an outbreak with 9,704 confirmed cases and 4,687 deaths in Congo as of Oct. 20, according to Africa CDC. Kenya has recorded nine cases, including one death, while Nigeria this week reported an imported case whose source of infection hasn’t yet been determined.

Screening at official border posts is also imperfect. Travelers crossing into Uganda from Congo are asked to declare their movements and possible exposure during the previous 21 days, have their temperature checked and are observed for signs of illness, according to the World Health Organization.

Those measures can miss infected travelers who aren’t yet feverish or visibly ill, or who don’t disclose their exposure, Patrick Otim, an emergency-response official at WHO’s Africa office, said in a separate briefing. People incubating Ebola aren’t contagious until they develop symptoms, but can cross a border undetected and become infectious after arriving in another country.

Kenya’s index case went to a hospital after flying from Uganda, where the initial diagnosis wasn’t Ebola. Health workers later suspected the virus after noticing bleeding at an injection site and considering his travel history, prompting his isolation and testing, Mankoula said. He died about 48 hours later despite receiving treatment.

Kenyan authorities subsequently identified 135 contacts, eight of whom developed Ebola while already in quarantine. Officials say that provides reassurance there isn’t established community transmission.

Still, Kenya has encountered problems maintaining infection controls inside quarantine. One facility wasn’t designed to adequately separate people and some continued to socialize and eat together despite being given individual rooms, according to Patrick Amoth, Kenya’s director-general for health. Authorities installed closed-circuit television cameras to monitor whether people remained in their rooms and reset the quarantine period for some contacts after another case was detected there.

There were also gaps in protecting health workers who handled the index case. Two nurses, a patient attendant and a biomedical technician were infected, and Amoth said many facilities had protective equipment designed for Covid-19 that wasn’t suitable for Ebola. Kenya has since distributed Ebola-specific protective gear to counties at the highest risk Nigeria presents another uncertainty.

Its first patient had spent more than two weeks in Uganda before flying from Entebbe on the same day as Kenya’s index case. She developed symptoms four days after arriving in Abuja and Africa CDC is investigating whether the two patients may have interacted at the airport, Mankoula said, stressing that the possibility hasn’t been verified.