Getting Ebola Under Control

Yesterday and today brought a few bits of good news:

According to the BBC, the Spanish nurse who was the first person to contract Ebola outside of West Africa has tested negative for the virus (a second test is required before she’ll be officially free of the disease). And the United States has reached an important milestone: the 21-day monitoring period for the 48 people who had contact with Thomas Eric Duncan, the Liberian man who died of Ebola in Dallas, ended on Sunday and Monday. Aside from the two nurses who cared for him, there have been no new infections.

Things are also looking up in Africa, where two countries have been declared Ebola-free:

On Friday, the World Health Organization announced that Senegal had completely contained the spread of the disease, and now on Monday Nigeria has joined them.

The ruling was made after determining that it has been six weeks without any new cases of the disease. The last reported case was on September 5. Seven Nigerians died of the disease since July, but the country is being praised for swift and decisive efforts to contain the outbreak. In particular, Nigerian officials quickly traced all those who came in contact with the first person to be diagnosed with the disease this summer.

Of course, none of this means the epidemic is over. The CDC is updating its safety guidelines for health workers in order to reduce the risk that other nurses will contract the virus if and when more Ebola patients arrive in American hospitals. And while the news from Senegal and Nigeria is worth celebrating, other West African countries remain in dire straits, with Liberian President Ellen Johnson Sirleaf warning that the disease has brought her country to a standstill:

“Across West Africa, a generation of young people risk being lost to an economic catastrophe as harvests are missed, markets are shut and borders are closed,” the Nobel Peace Prize laureate said in a “Letter to the World” broadcast on Sunday by the BBC. “The virus has been able to spread so rapidly because of the insufficient strength of the emergency, medical and military services that remain under-resourced.”

In neighboring Sierra Leone, emergency food rations were distributed for a third day on Sunday to give a nutritional lifeline to 260,000 residents of an Ebola-stricken community on the outskirts of the capital, Freetown. The Waterloo area in Freetown has 350 houses under quarantine with people suspected of having the Ebola virus and infections in the district are rising, according to the UN World Food Program.

Meanwhile, one new study suggests that the 21-day monitoring period may not always be long enough:

According to Charles Haas of Drexel University, who authored the study, the exact scientific origins of the World Health Organization’s recommended quarantine period for Ebola are murky. The recommendation could be traced to data from the 1976 Ebola outbreak in Zaire and the 2000 outbreak in Uganda, both of which reported incubation periods of 2-21 days, but nobody can be certain.

A more concrete approach is needed to determine an appropriate quarantine period, Haas wrote, so he analyzed data from the 1995 outbreak in the Congo and the current one in West Africa. After examining the newly expanded data set, Haas discovered that the probability of excedence for Ebola incubation was .1 to 12 percent. “In other words,” he wrote, “from 0.1 to 12 percent of the time, an individual case will have a greater incubation time than 21 days.”