Could the current Ebola outbreak spread to Europe and other continents?

With yet another outbreak of Ebola in Africa, should people be worried about the virus making its way beyond the continent?

On Tuesday, the World Health Organization's head expressed concern over the "scale and speed of the epidemic", raising concerns about how quickly and how far the virus is spreading.

It comes as the Congolese health ministry said on Tuesday that at least 131 deaths and over 500 suspected cases have been reported in the latest Ebola outbreak in eastern Congo.

The virus spread undetected for at least a few weeks since the first person died of the virus, health experts and aid workers said, and the delayed response is now complicating efforts to curb the outbreak.

Congo's health minister, Samuel Roger Kamba, said 513 suspected cases and 131 deaths have been recorded, though he added "these are suspected deaths, and investigations are underway to determine which ones are actually linked to the disease".

Could this be the next global pandemic?

The numbers mark a sharp increase from Monday, when officials said there were 300 suspected cases, and highlight the largely unknown scale of the outbreak.

The World Health Organization's director-general, Tedros Adhanom Ghebreyesus, said he is "deeply concerned about the scale and speed of the epidemic", and the UN health agency is set to convene its emergency committee later on Tuesday.

He said the emergence of cases in urban areas, the deaths of healthcare workers, significant population movement in the area, and a lack of vaccines and therapeutics are the main reasons for concern "for further spread and further deaths".

Health authorities say the outbreak, first confirmed on Friday, is caused by the Bundibugyo virus, a rare variant of the Ebola disease that has no approved therapeutics or vaccines.

The WHO declared the Ebola outbreak a public health emergency of international concern on Sunday.

Cases have been confirmed in Bunia, North Kivu's rebel-held capital of Goma, Mongbwalu, Butembo, and Nyakunde.

There has also been one case and one death reported in Uganda in people who traveled from Congo.

It emerged last week that a US national has tested positive for the Ebola virus following exposure while serving with a medical missionary group in the Democratic Republic of Congo.

The US Centers for Disease Control and Prevention then moved to invoke Title 42, a public health statute that permits the restriction of entry into the United States during outbreaks of communicable diseases, for a minimum of 30 days, effective as of Monday.

Enacted in 1944, Title 42 has been invoked just twice in modern history.

Its first application spanned from March 2020 to May 2023 in response to the Covid-19 pandemic; Monday's declaration regarding Ebola marks only the second time the public health statute has been utilized.

So as the US moves to make sure the virus does not reach its shores, how worried should the world be about this outbreak becoming the next global pandemic?

Concerns are warranted, but global risk remains low

While some countries were quick to deploy measures devised to curb the chances of the Ebola virus getting in, and the WHO is understandably concerned, based on previous outbreaks, the chance of the current one spreading across other continents is very low.

Experts from the School of Public Health at Imperial College London note that during the West African epidemic between 2013 and 2016, just a small number of cases were recorded in Europe despite nearly 30,000 infections across the region; most of these instances involved international healthcare workers who were repatriated after contracting the virus while serving in the field.

But while there is no documented sustained spread of Ebola outside of Africa, the risk of the current outbreak spreading further across the continent remains high.

The African Centers for Disease Control stated on May 15 that there is risk to both the rest of the DRC and nearby countries of Uganda and South Sudan due to their geographical proximity and high connectivity within the affected regions.

So what are some of the reasons behind the virus being able to spread so quickly?

False negative Ebola tests delayed the response

One of the reasons the virus is spreading quickly is because it remained undetected for at least a few weeks since the first death, and the delayed response makes efforts to curb the outbreak more difficult.

Congo has said the first person died from the virus on April 24 in Bunia, and the body was repatriated to the Mongbwalu health zone, a mining area with a large population.

"That caused the Ebola outbreak to escalate," said Kamba, the health minister.

When another person fell ill on April 26, samples were sent to Kinshasa for testing, according to the Africa Centers for Disease Control.

Samples from Bunia were initially tested for the more common type of Ebola - Zaire - according to Congolese officials.

They came back negative, said Dr. Richard Kitenge, the Health Ministry Incident Manager for Ebola, and local authorities assumed it was not Ebola.

On May 5, the WHO was alerted to about 50 deaths in Mongbwalu, including four health workers, which prompted further tests.

The first confirmation of Ebola came on May 14.

Matthew M. Kavanagh, director of the Georgetown University Center for Global Health Policy and Politics, said that because of the false negative tests, "we are playing catch-up against a very dangerous pathogen".

He criticized the Trump administration's earlier decision to withdraw from the WHO and make deep cuts in foreign aid—"the exact surveillance system meant to catch these viruses early," he said.

The US State Department pushed aside criticism on Monday, saying that it sprang into action immediately and has already provided $13 million in assistance for the response.

Esther Sterk with the Médecins Sans Frontières aid group said that "the situation is quite worrying and is evolving pretty quickly".

"It was detected quite late," she added.

But she said that was often the case with outbreaks of Ebola, which has similar symptoms to other tropical diseases.

Less lethal, but still extremely dangerous

Another reason why the virus is spreading at such a pace is the fact that Ebola is highly contagious.

And while from the few outbreaks health experts have seen, Bundibugyo might be slightly less deadly than what is often called the Zaire virus, the most common species, its 30%-plus mortality rate makes it still extremely dangerous.

It causes fever, headache, muscle pain, weakness, diarrhea, vomiting, stomach pain, and unexplained bleeding or bruising.

The virus is spread the same way as other Ebola viruses: through close contact with sick or deceased patients' bodily fluids, such as sweat, blood, feces, vomit, or semen.

Healthcare workers and family members caring for sick patients face the highest risk, experts said.

During a big Ebola outbreak over a decade ago, which killed over 11,000, many got infected while washing bodies during community funerals.

"Ebola is very much a disease of compassion in that it impacts the people who are more likely to be taking care of sick folks," said Dr. Craig Spencer, an associate professor at the Brown University School of Public Health who survived Ebola more than a decade ago after contracting the disease in Guinea.

The region already grapples with a humanitarian crisis

The rapid transmission is further exacerbated by the fact that the affected region is already navigating a severe humanitarian crisis.

Ituri's Mongbwalu is in remote eastern Congo, with poor road networks more than 1,000 kilometers from the capital, Kinshasa.

Eastern Congo has grappled with a humanitarian crisis and the threat of armed groups that have killed dozens and displaced thousands in Ituri in the past year.

Ituri has over 273,000 displaced people out of a population of 1.9 million, according to the UN.