Twenty-six more suspected Ebola deaths were recorded in 24 ​hours in eastern Democratic Republic of Congo, authorities said on Tuesday, and the head of the World Health ‌Organisation expressed deep concern about the outbreak’s spread.

The new deaths bring to 131 the fatalities associated with the outbreak in eastern DRC. There have been 516 suspected cases and 33 confirmed cases in Congo, according to a daily bulletin published by health authorities, and two confirmed cases in neighbouring Uganda.

WHO Director-General ​Tedros Adhanom Ghebreyesus declared the outbreak of the rare Bundibugyo strain of the virus a public health emergency of ​international concern on Saturday. It has alarmed experts because it was able to spread for weeks undetected across ⁠a densely populated part of Congo.

Butembo, a city of hundreds of thousands of people in Congo’s North Kivu province, recorded its ​first two confirmed cases on Monday, Jean-Jacques Muyembe, director of Congo’s National Institute for Biomedical Research (INRB), told Reuters.

Americans to be evacuated to Germany

Ebola spreads through direct contact with bodily fluids from infected people or animals and causes symptoms that can include high fever, vomiting and internal and external bleeding. According to the WHO, the average fatality rate from Ebola is around 50%, varying from 25% to 90% in past outbreaks.

“I’m deeply ​concerned about the scale and speed of the epidemic,” Tedros told members of the World Health Assembly in Geneva on Tuesday, ​citing the number of cases being reported in urban areas and among healthcare workers.

One American tested positive for Ebola as part of their work in ‌Congo, ⁠the US Centres for Disease Control and Prevention said on Monday.

The individual, identified as Dr Peter Stafford by his Christian mission organisation, and six other Americans who were exposed to the virus are being moved to Germany for care and monitoring, the CDC said.

The US State Department said it had mobilised an initial $13 million in foreign assistance for immediate response efforts to the outbreak.

Experts try to develop treatments and vaccines

Unlike with ​the more common Zaire strain ⁠of Ebola, there are no approved virus-specific therapeutics or vaccines for the Bundibugyo strain.

The US is working to develop a monoclonal antibody therapy as a potential treatment, the CDC said on Monday.

A panel ​of experts led by the WHO will also meet on Tuesday to discuss if there ​are any vaccine ⁠options to help tackle the outbreak.

The US officially left the WHO in January in a move President Donald Trump said was motivated by the organisation’s poor management of the COVID-19 pandemic.

An outbreak of the Zaire strain from 2018-2020 in Ituri and North Kivu provinces was the ⁠second deadliest ​on record, killing nearly 2,300 people. The international response then was complicated ​by widespread armed violence in eastern Congo that continues today.

One Ebola case has been confirmed in North Kivu province’s capital, Goma, which was seized by M23 rebels ​last year.