Ebola already reached the US when a patient was diagnosed in Texas on September 30. But where is the disease likely to go next? A map from MOBS Lab and Northeastern University shows the risks:

risk of ebola spread


To develop these estimates, researchers used a computer model that tracks the frequency of international traffic to different countries, the progression of the disease in already affected countries, and the incubation time and other aspects of Ebola. The estimates will be updated as the epidemic continues.

Outside of Africa, the risk is relatively high in the UK and France, but thankfully very low in India and China. The more advanced health-care systems in the UK and France are much better equipped to deal with an Ebola outbreak, while less advanced systems in China and particularly India, which also have considerably bigger populations to manage, could struggle to deal with an epidemic.

Peter Piot, who helped discover and name the virus, told the Guardian about his concerns with an outbreak in India:

But an outbreak in Europe or North America would quickly be brought under control. I am more worried about the many people from India who work in trade or industry in west Africa. It would only take one of them to become infected, travel to India to visit relatives during the virus’s incubation period, and then, once he becomes sick, go to a public hospital there. Doctors and nurses in India, too, often don’t wear protective gloves. They would immediately become infected and spread the virus.

As Vox’s Julia Belluz previously explained, this is one of the nightmare Ebola scenarios that keeps scientists up at night. It’s good, then, that the chance of Ebola spreading to India and China seems fairly remote.

The CDC is trying to ensure Ebola doesn’t spread in the US

Officials are following up with the people who had some exposure to the Dallas patient, Thomas Duncan, and the health-care worker who cared for him and tested positive for the disease.

To track these people, they’ll use one of the tried-and-true methods for stopping the disease from spreading further: “contact tracing.” This public-health measure works exceptionally well for small-scale outbreaks, like the one in Texas.

According to the CDC director Tom Frieden, everyone who came in contact with Texas patient Thomas Duncan while he was infectious has been identified. Identifying those who may have been exposed basically involves the work of a detective. Freiden says health officials interview the patient and then their family members and close contacts. From there, officials will outline and investigate all of the patient’s movements before the patient was in isolation and during the period when he could have been contagious.

They then build “concentric circles,” the closest representing the people who the patient could have exposed, and a second with all the other people those initial contacts may have interacted with.

“This is core public health and it is what we do day in and day out and what we will be doing here to identify any possible spread and to ensure there aren’t further chains of transmission,” says Frieden.

Those at risk are watched for 21 days — the incubation period for the virus — to make sure they don’t develop symptoms. Their temperature is taken twice daily. If they show symptoms, they are placed in isolation and tested for the virus. If they don’t, after 21 days, they are declared risk free.

The CDC is also taking other precautionary measures. With the Department of Homeland Security, the agency announced that airport officials would begin screening flight passengers coming in from West Africa for signs of infection. For more on Ebola and airport screening, see here.