STOCKHOLM, Sweden (AFP)— Health authorities warned Europe Friday to get ready for more cases of a deadly strain of mpox that has killed hundreds of people in the Democratic Republic of Congo.

China said it would screen travellers for the disease after the first cases of the new, more deadly strain to be recorded outside Africa were announced in Sweden and Pakistan.

The infectious virus is caused by a virus transmitted to humans by animals but can also spread human-to-human through close physical contact.

It causes fever, muscular aches and large boil-like skin lesions.

The World Health Organization (WHO) on Wednesday declared the rapid spread of the new strain, dubbed Clade 1b, a public health emergency of international concern — the highest alarm the UN agency can sound.

The Stockholm-based European Centre for Disease Prevention and Control (ECDC) said Friday that the overall risk for the general population in Europe was “low” but urged countries to be prepared to detect it.

It said that “ensuring effective surveillance, laboratory testing, epidemiological investigation and contact tracing capacities will be vital to detecting cases” on the continent.

“Due to the close links between Europe and Africa, we must be prepared for more imported clade I cases,” ECDC director Pamela Rendi-Wagner said in a statement.

The virus has swept across the Democratic Republic of Congo, killing 548 people so far this year, the country’s Health Minister Samuel-Roger Kamba said on Thursday.

Nigeria has also recorded 39 cases of mpox since the beginning of the year — none of them fatal — Jide Idris, the director-general of the Nigeria Centre for Disease Control and Prevention, told reporters.

Previously unaffected countries such as Burundi, Kenya, Rwanda and Uganda have also reported outbreaks, according to the Africa Centres for Disease Control and Prevention.

Sweden’s Public Health Agency told AFP on Thursday it had registered a case of Clade 1b — the first such infection outside Africa.

The patient was infected during a visit to “the part of Africa where there is a major outbreak of mpox Clade 1”, epidemiologist Magnus Gisslen said in a statement from the agency.

The mpox strain that caused the case in Pakistan was not immediately known on Friday, the health ministry said in a statement.

It said the patient had “come from a Gulf country”.

The Pakistan patient is a 34-year-old man and “the first confirmed case we have this year” of mpox, said Irshad Roghani, director of public health in Khyber Pakhtunkhwa province, where the man is being treated.

Mpox has two subtypes: the more virulent and deadlier Clade 1, endemic in the Congo Basin in central Africa; and Clade 2, endemic in West Africa.

A worldwide outbreak beginning in 2022 involving the Clade 2b subclade caused some 140 deaths out of around 90,000 cases, mostly affecting gay and bisexual men.

The US Department of Health said Wednesday it would donate 50,000 doses of an mpox vaccine to DRC, saying inoculation would “be a critical element of the response to this outbreak”.

Danish drugmaker Bavarian Nordic said it would be ready to produce up to 10 million doses of its vaccine targeting mpox by 2025.

The WHO’s European regional office in Copenhagen said in a statement that the Sweden case was “a clear reflection of the interconnectedness of our world”.

But it added: “Travel restrictions and border closures don’t work and should be avoided.”