CDC models project current Ebola outbreak could rival 2014 West Africa epidemic

What the models project

The outlook worsens sharply when isolation is delayed. "If only 20% of cases enter isolation within two days of symptom onset, more than 20,000 cases are projected in two out of three of our scenarios," Asher said. By contrast, "If 70% of cases started isolating within that two-day period, there's a 94% probability of limiting the outbreak to fewer than 10,000 cases," he added. The CDC has identified isolation of exposed individuals as the single most important factor in limiting transmission.

World Health Organization tallies released on Saturday showed 452 confirmed cases in the Democratic Republic of Congo and 19 in Uganda, a combined total of 471. The DR Congo figures marked an increase of 100 cases and 20 deaths from the previous day, and 82 deaths have been counted in the country. The outbreak in DR Congo was declared roughly three weeks before the WHO update.

Scale of the 2014 epidemic

The WHO has declared the outbreak an international health emergency. Public health researchers said the trajectory described in the CDC models is consistent with the spread already documented on the ground. "The analysis affirms what we have worried about since the beginning: This outbreak is following a dangerous trajectory and will get a lot worse unless we do more to stop it at its source," said Jennifer Nuzzo, director of the Pandemic Center at Brown University School of Public Health.

The 2014-2016 West Africa Ebola outbreak remains the largest on record, with about 28,000 cases and more than 11,000 deaths. A CDC official said on Friday that current models indicated the present outbreak risked rivalling that scale in the absence of strong interventions. Satish Pillai, the CDC's Ebola response incident manager, said the agency's focus is on containment where the virus is spreading.

Risk outside the outbreak zone

Pillai stressed that the danger to people outside the affected region is limited. "The domestic risk remains low for the general US population," he said, adding that there is no reason for people to change their behavior or alter international travel plans other than to the Democratic Republic of Congo or Uganda. One of the three CDC papers specifically concludes that the risk of Ebola to the United States remains low.

Calls for a stronger international response

Conditions in the outbreak zone are complicating the response. The CDC has noted that active conflict and difficulties accessing healthcare are hampering efforts in parts of the region. The case and death numbers cited by the WHO were reported by the governments of DR Congo and Uganda.

Former U.N. official Anthony Banbury, who led the U.N. Mission for Ebola Emergency Response, published an opinion piece in The Washington Post on Thursday warning that the crisis would spiral without a major shift in the international response. "Ebola crisis in Africa will spin out of control without a significant shift in the international response," Banbury wrote. The CDC's Pillai echoed the urgency on the ground: "Our goal is control, containment and ending the outbreaks in DRC and Uganda. And we are working every day towards that goal."