WHO Director-General Dr Tedros Adhanom Ghebreyesus expressed deep concern as the reported cases rose, saying: “I determine that the epidemic constitutes a public health emergency of international concern”.

But he added that the threat “does not meet the criteria of pandemic emergency”.

As things stand, the Geneva-based WHO has declared its second-highest level of alert – a pandemic being the highest – with the global health body warning the scale of the current outbreak remained unclear.

In a statement the WHO said: “There are significant uncertainties to the true number of infected persons and geographic spread”.

Medical aid group Doctors Without Borders (MSF) said it was preparing a “large-scale response”, calling the rapid spread of the outbreak “extremely concerning”.

DRC’s Health Minister Samuel-Roger Kamba said the Bundibugyo strain – first identified in 2007 – causing the outbreak had “a very high fatality rate, which can reach 50%”.

Uganda announced the postponement of the Martyrs’ Day pilgrimage, an annual Christian festival that normally draws thousands of worshippers from across the border in eastern Congo.

Vaccines are only available for the Zaire strain, which was identified in 1976 and has a higher fatality rate of 60%-90%.

Patient zero is reported as being a nurse who reported to a health facility in Ituri’s provincial capital Bunia on April 24, with symptoms suggesting Ebola.

Symptoms of the disease include fever, haemorrhaging and vomiting.

Large-scale transport of medical equipment is a challenge in the DRC, a country of more than 100 million people with poor communications infrastructure.

It is the 17th Ebola outbreak to hit Congo, and officials warned of a high risk of spread. With the outbreak largely concentrated in difficult-to-access areas few samples have been lab tested.

But the WHO said the high positivity rate of initial samples, the confirmation of cases in two countries, and the increasing reports of suspected cases “all point towards a potentially much larger outbreak than what is currently being detected and reported, with significant local and regional risk of spread”.

The previous outbreak of Ebola was last August in the region, with at least 34 people dying before it was declared eradicated in December.

The disease, over the past 50 years, has killed around 15,000 people in Africa, despite advances in vaccines and treatment.

Nearly 2300 people died in the deadliest outbreak in the DRC between 2018 and 2020.

Ebola, believed to have originated in bats, can cause severe bleeding and organ failure.

Outbreaks over the past half a century have seen a mortality rate among those affected of between 25% and 90%, according to WHO.

The virus spreads from person to person through bodily fluids or exposure to the blood of an infected persons, who become contagious only once they display symptoms. The incubation period can last up to 21 days.

– AFP