Kenya reported its first death from a deadly strain of Ebola virus which had spread widely, starting in the Democratic Republic of Congo earlier this year.

The Bundibugyo (BDBV) strain of Ebola was first detected in Uganda in 2007, according to the WHO. The ongoing outbreak in the DRC has killed at least 4,148 people out of 8,300 reported cases. It also spread across the border to Uganda, which had about 20 cases before being declared Ebola-free in July.

However, the person who died in Kenya from the disease had travelled from the DRC to Uganda over land before taking a flight to Nairobi, raising questions about Uganda’s status as “Ebola-free”, concerns about the rigidity of Kenya’s screening processes for people coming into the country and fears it may have spread further than previously thought.

On Tuesday, the World Health Organization said the Kenyan government is now enhancing its disease surveillance with more targeted screening at high-risk points of entry.

But Wolfgang Preiser, a professor and head of medical virology at Stellenbosch University in South Africa, explained that while efforts are being made to bring the outbreak under control, it has grown so much that “sheer numbers and the speed of spread are overwhelming for many systems.”

“I am not surprised that cases have reached other provinces in DRC and neighbouring countries. I expect that this will continue to happen until such time that the trajectory has been reversed and case numbers are in decline,” he told Al Jazeera.

Here’s what we know:

What is Ebola?

It is a serious, potentially deadly viral infection which can be caught when a person comes into contact with the bodily fluids of an infected person or wild animal, including fluid lingering on surfaces. People have also been known to contract the disease through eating contaminated meat.

There have been many outbreaks in Central, West and East Africa.

A West African outbreak from 2014 to 2016 killed at least 11,300 people of a reported 28,600 cases and accelerated the push to develop a vaccine. That was a different strain of the Ebola virus, known as Zaire, for which there is now a vaccine.

The strain behind the latest outbreak is Bundibugyo virus (BDBV), which is believed to have been caused by a new transmission from animals to humans, before then spreading between humans, rather than by variants linked to earlier outbreaks. There is no vaccine for Bundibugyo.

Symptoms can appear between two and 21 days after infection and can start suddenly with flu-like symptoms, including a high temperature, fatigue, and a headache. It can lead to internal and external bleeding, impaired liver and kidney function and organ failure.

How did this case of Ebola reach Kenya?

Kenyan Health Minister Aden Duale told reporters that the Kenyan patient, who has not been named, first became sick one month ago in the DRC, where they had been living for several years, and was treated there.

On October 2, the patient travelled by road to the Ugandan capital, Kampala, via Beni, then flew to Nairobi, arriving the next day.

After he arrived at the airport in Kenya, a relative and a friend took him to a hospital, where he was quickly isolated, and tests showed he had the virus, Duale said. Despite receiving care, the patient died from the virus on Monday and was buried on Tuesday in line with the country’s Ebola protocol.

So far, health authorities in Kenya have identified 28 potential contacts, including family members and health workers who cared for the infected patient. Authorities are also separately tracking 23 passengers and four crew members from his flight, “with arrangements underway for appropriate follow-up and quarantine of people assessed to be at risk”, the WHO reported.

Jean Bisimwa Nachenga, a professor in infectious diseases at Stellenbosch University, emphasised that the virus does not “respect national borders.”

“Population mobility, displacement, cross-border trade, and fragile healthcare systems make containment particularly challenging. In eastern DRC, ongoing insecurity further complicates surveillance, contact tracing, and access to affected communities,” he told Al Jazeera.

“Regional cooperation is therefore essential.”

How did a sick patient get past screening in both Uganda and Kenya?

Passengers travelling to, from or through Uganda and Kenya have to pass multiple airport temperature checks and complete at least two digital forms intended to flag any potential exposure to the virus in the DRC. Somehow, the infected person in this case was missed by these checks.

Ugandan government spokesperson Alan Kasujja said Kampala was not to blame for the Kenyan man catching the virus and wrote on X, “Leave Uganda out of this conversation. We don’t have Ebola here.”

In a statement issued on Tuesday, the Ugandan Ministry of Health said the man had a “normal temperature” when he was screened at the Entebbe airport before his departure.

Kenyan authorities say he may have taken medication to mask his symptoms when he was later screened at Nairobi airport. Investigations are continuing, however.

“We are trying to retrieve the digital form he would have filled out at Entebbe airport when he went through the thermal scanning process to see what he declared in that form. The form includes questions about recent health problems but also whether a traveller was recently in DRC,” Richard Mugahi, a senior Ugandan health official, told the Reuters news agency.

“We are also going through airport security camera footage to see if we can identify the driver who dropped him at the airport so we can trace any contacts here.”

Preiser also said the tracking system “seems to work as it did in Uganda,” with a diagnosis made rapidly as soon as the patient sought care in Kenya.

“It will be instructive to try and trace back what happened at the various stops during his travels, and lessons should be heeded by all countries,” he said.

He cited an example from a previous Ebola outbreak in West Africa, when a “British nurse fell sick during her return trip to the UK and reported to the medical check in Heathrow, only to be sent onwards to her destination where she was diagnosed with Ebola”.

The lesson, he said was that “even cooperative travellers and good systems may fall through the net”.

Where else has Ebola spread?

Since it began in the DRC’s northeastern Ituri province, the latest outbreak has spread this year to seven provinces in the country’s north and east. It was officially declared an outbreak in the DRC in May.

Weak infrastructure, the remoteness of the region in eastern DRC, and ongoing conflict with armed groups near the borders with South Sudan, Uganda, and Rwanda have hindered efforts to respond to cases quickly and effectively.

The response to the outbreak has been further complicated by several factors, including strikes by unpaid health workers, misinformation and cultural traditions. These have included open-casket family burials of some of those killed by the virus earlier on during the outbreak, potentially increasing the risk of further transmission.

The United Nations reported on Friday last week that an Ebola-hit camp housing a transit centre for infected patients was burned by soldiers earlier this week when they were looking for weapons on the outskirts of Bunia, the capital city of Ituri province, which is at the epicentre of the outbreak.

The incident forced 19,000 people to flee the camp.

The disease also spread to Uganda, where 20 people who had travelled from DRC were treated before the country declared it was free of Ebola in July.

Recently, it has become increasingly hard to contain within DRC.

On Monday, Doctors Without Borders, known by its French initials MSF, warned that there had been an “alarming surge” of cases in eastern North Kivu province, which borders Uganda, and where 40 percent of all new cases are currently being recorded.

“It is like fighting a megafire,” Stephanie Hoffmann, coordinator at MSF’s Ebola treatment centre in the city of Butembo, said. “Multiple outbreaks are developing at the same time, with varying intensity and in different locations.”

Some 2 million people live in North Kivu’s city of Butembo and surrounding areas, but it has only four Ebola treatment centres, two of which opened recently, MSF told the media. Patients often have to be transferred elsewhere, increasing the risk of infection to others, Hoffman said.

What happens now?

The WHO is working with Kenyan authorities to trace contacts and to strengthen checks for travellers coming into the country.

Mohamed Janabi, WHO regional director for Africa, said on Tuesday that “health emergency preparedness gives us a head start”.

“Kenya has put important outbreak control measures in place. The priority now is to move swiftly to detect any further cases before the virus has an opportunity to spread. We’re supporting the ongoing efforts to strengthen the response, and with rapid and coordinated action, we can prevent the virus from gaining a foothold and stop a potential larger outbreak,” Janabi said.

The agency also said it has delivered about 1,000 Ebola tests and “1,000 personal protective equipment kits to high-risk counties in Kenya”.

In June, the Kenyan government granted the United States permission to set up an Ebola quarantine facility at the Laikipia airbase, 120 miles (193km) from the capital, Nairobi, to treat infected Americans travelling from African nations before they arrived in the US. The scheme generated uproar from locals who feared transmission of the disease, and Kenyan courts halted the plan.

Overall, Nachenga said that merely strengthening border screening wasn’t enough. It was also important to “reinforce the entire public health response”.

“This means training frontline healthcare workers, ensuring rapid laboratory diagnosis, promptly isolating suspected cases, and tracing and monitoring contacts. Kenya’s ability to identify this case provides an important opportunity to strengthen preparedness,” he added.