Chinese health authorities said on Thursday they had detected the new mutated mpox strain clade Ib as the viral infection spreads to more countries after the World Health Organization declared a global public health emergency last year.

China's Centre for Disease Control and Prevention said it had found a cluster outbreak of the Ib subclade that started with the infection a foreigner who has a history of travel and residence in the Democratic Republic of the Congo.

Four further cases have been found in people infected after close contact with the foreigner. The patients' symptoms are mild and include skin rash and blisters.

Mpox spreads through close contact and causes flu-like symptoms and pus-filled lesions on the body. Although usually mild, it can be fatal in rare cases.

WHO last August declared mpox a global public health emergency for the second time in two years, following an outbreak in the Democratic Republic of Congo (DRC) that spread to neighbouring countries.

The outbreak in DRC began with the spread of an endemic strain, known as clade I. But the clade Ib variant appears to spread more easily through routine close contact, including sexual contact.

The variant has spread from DRC to neighbouring countries, including Burundi, Kenya, Rwanda and Uganda, triggering the emergency declaration from the WHO.

China said in August last year it would monitor people and goods entering the country for mpox.

The country's National Health Commission said mpox would be managed as a Category B infectious disease, enabling officials to take emergency measures such as restricting gatherings, suspending work and school, and sealing off areas when there is an outbreak of a disease.