NEW YORK — The Ebola outbreak in Central Africa could grow to 20,000 cases or more, depending on how quickly infected people are isolated to slow the spread, according to a new analysis by U.S. health officials.
The Centers for Disease Control and Prevention published a range of scenarios generated by computer models Friday, spanning from 10,000 cases to more than 20,000. If accurate, a worst-case scenario could approach the worst Ebola outbreak in history, the West Africa epidemic in 2014-2016 — which resulted in more than 28,000 reported cases and more than 11,000 deaths.
“Without strong public health interventions, the modeling work suggests an outbreak of that scale is possible,” said Satish Pillai, incident manager for the CDC’s Ebola response, in a briefing with reporters.
Jennifer Nuzzo, director of Brown University’s Pandemic Center, said the modeling “affirms what we have worried about since the beginning: This outbreak is following dangerous trajectory” if more is not done to stop the spread of Ebola.
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 added.
The Africa Centers for Disease Control and Prevention said Friday that there have been about 400 confirmed cases, including 63 deaths. Experts say there likely others that haven’t been diagnosed or reported.
Viruses that cause Ebola disease spread through contact with bodily fluids 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.
Earlier this week, Nuzzo said the risk to the United States seems low. “I don’t think it’s a scenario that it’s going to come here and spread broadly,” she told reporters. The CDC echoed that assessment in a paper released Friday.
That’s due in part to decisions but the U.S. government to ban the entry of people without U.S. passports, as well as U.S. green-card holders who visited Congo, Uganda, or South Sudan in the previous 21 days. Also, people with U.S. passports who traveled to those countries are undergoing health screenings and being funneled into four receiving airports.
CDC’s modeling report attempts to project how things might play out, depending on different factors — including how many infections and deaths have already happened, and how successful responders are in quickly identifying and isolating infected people before they can spread the infection to others.
Assuming around 50 people had died and about 20% of infected persons were successfully isolated by late May, most simulations suggest at least 20,000 cases and 4,000 deaths will occur in Africa over three months.
Pillai said the actual isolation rate is unknown but is considered to be “on the lower end of the scenarios” that CDC modeled.
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 that currently recognized, that could make the outcomes worse, CDC officials said.
Some CDC modeling during the large Ebola outbreak in West Africa proved to be way off. The CDC issued modeled numbers in 2014, when the epidemic was spiraling out of control and international health officials were quickly trying to build a response.
The CDC 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.
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