Central Africa’s Ebola outbreak could spread to be similar in scale to the worst outbreak in history, west Africa’s 2014-2016 outbreak that killed more than 11,000 people, according to a new analysis by US health officials.

The US Centers for Disease Control and Prevention (CDC) on Friday published a range of scenarios generated by computer models, from 10,000 cases to more than 20,000. In the west Africa outbreak, more than 28,000 cases were reported.

The analysis from the CDC said cases could grow to 20,000 or more, depending on how quickly infected people are isolated to slow the spread.

Incident manager for the CDC’s Ebola response, Dr Satish Pillai, said without strong public health interventions, “the modelling work suggests an outbreak of that scale is possible”.

Jennifer Nuzzo, director of Brown University’s Pandemic Center in the United States, said the modelling “affirms what we have worried about since the beginning: this outbreak is following dangerous trajectory” if more is not done to stop its spread.

But she cautioned it can be extremely difficult to predict how outbreaks will progress. “I wouldn’t read too much into the specific numbers. It’s really hard to make an accurate projection when you have limited data,” she said.

The Africa Centers for Disease Control and Prevention said Friday there have been about 400 confirmed cases, including 63 deaths. Experts say there are probably other cases that haven’t been diagnosed or reported.

The viruses that cause Ebola are spread through contact with body fluid such as vomit, blood and semen. There are no specific treatments or vaccines for the Bundibugyo virus at the heart of the current outbreak. The disease is often fatal.

The World Health Organization declared the outbreak a global health emergency in May. Some experts believe infections may have been occurring in February, but health officials initially tested for a different kind of Ebola virus.

The outbreak response has been complicated by an armed conflict between Congo’s government and the Rwanda-backed M23 rebel group, as well as attacks by the Islamic State-affiliated group the Allied Democratic Force. The violence has caused massive displacement of people living in the conflict areas, officials say.

CDC’s modelling report attempts to project how things might play out, based on different factors – including how many infections and deaths have already happened, and how quickly responders can identify and isolate infected people before they can spread the infection to others.

Pillai said the actual isolation rate is unknown but is considered to be “on the lower end of the scenarios” that CDC modelled.

Higher isolation rates, of 50% or 70%, could result in the number of cases being more like 10,000, CDC officials said. But if the actual number of deaths were greater in late May than now recognised, that could make the outcomes worse, CDC officials said.

Some CDC modelling during the large Ebola outbreak in West Africa proved to be way off. The CDC issued modelled numbers in 2014, when the epidemic was spiralling out of control and international health officials were quickly trying to build a response.

It estimated that in a worse-case scenario where nothing was done, as many as 1.4 million people might become infected. That turned out to be more than 50 times higher than what happened.