Nearly 500 Ebola cases have now been confirmed in the deadly outbreak raging in central Africa, a WHO overview showed on Saturday, amid mounting concern over the swelling scale of the epidemic.

In its daily update on the situation, the World Health Organization tallied 452 confirmed cases, including 82 deaths, in the Democratic Republic of Congo (DR Congo), where the outbreak was declared three weeks ago.

In neighbouring Uganda, meanwhile, it counted 19 confirmed cases, including two deaths.

The total of 471 cases and 84 deaths, based on numbers reported by the governments of DR Congo and Uganda, marked an increase of 100 cases and 20 deaths from a day earlier.

The increase came amid warnings that the outbreak, which the WHO has declared an international public health emergency, could eventually swell to become the largest on record.

A top official at the US Centres for Disease Control and Prevention (CDC) said on Friday that models indicated that without strong public health interventions, the current outbreak risked rivalling the scale of the 2014 West Africa epidemic, which saw over 28,000 cases and more than 11,000 deaths.

“That scale is possible,” said Jason Asher, director of the CDC’s Centre for Forecasting and Outbreak Analytics, during a press briefing.

Ebola, which is spread through close contact and bodily fluids, has killed more than 15,000 people in Africa over the past 50 years.

The current outbreak was declared on May 15 in northeastern DR Congo, but the virus is believed to have spread under the radar for some time beforehand.

There are no approved vaccines or treatments for the rare Bundibugyo species of Ebola behind the outbreak.

The WHO and the African CDC on Friday launched a US$518 million plan to battle the outbreak over the next six months, focusing among other things on boosting surveillance, laboratory testing and infection prevention.

“The outbreak is moving fast, and we are still playing catch-up,” WHO chief Tedros Adhanom Ghebreyesus told reporters.

“We need to stop the outbreak where it is, support countries that are responding today, and ensure that neighbouring countries are ready to detect and act quickly if cases appear,” he said.

“This is a serious outbreak and its one we know how to stop but we need to move fast and together.”