Hunting Ebola in Freetown: A day in the life of an epidemiologist

April 2015

Sometimes described as disease detectives, epidemiologists play a crucial role in every outbreak. "Our job is to find every single link. We need to find out who infected whom, how, and where" says Dr Katrina Roper, a WHO epidemiologist working in Freetown, Sierra Leone.

Today more WHO outbreak responders are working at the community level in West Africa than at any other point in the epidemic. People like Dr Roper and her colleagues will continue walking every mile, reaching every corner and doing what is needed to bring the Ebola outbreak to an end.

We followed Dr Roper for a full day as she tracked the virus in the streets, alleys and homes of Freetown, searching every nook and cranny for signs of Ebola.


Dr Roper, WHO epidemiologist, is discussing an Ebola case investigation with  a colleague from Medecins Sans Frontieres, Sierra Leone
WHO/D. Licona

8 a.m.: Joining forces

First thing in the morning all the partners meet at the District Emergency Response Centre to exchange information and get updates on case investigations. The goal is to know exactly how every person got infected, identify them and prevent further spread of Ebola infections. Here Dr Roper is discussing an ongoing investigation with a colleague from Medecins Sans Frontieres (MSF). The Ministry of Health of Sierra Leone and other partners like the US Centres for Diseases Control and the African Union are also actively performing epidemiological work in the district.


An aerial view of the wards Dr Roper, WHO epidemiologist, was assigned to investigate Ebola cases, Sierra Leone
WHO/D. Licona

9 a.m. Reaching every corner

Ebola investigators need to reach every single corner of the district to solve cases. Each epidemiological team has been assigned a number of wards, but since the virus does not respect borders, investigations between wards are conducted. That is why sharing information is so important. Here is an aerial view of the wards Dr Roper has been assigned to investigate.


Dr Roper, WHO epidemiologist, talks to community members about suspect cases (Ebola), Sierra Leone
WHO/D. Licona

10 a.m.: A long morning

As the morning wears on, Dr Roper asks contacts (people who have been in contact with confirmed cases) multiple questions and fills in the form.

Epidemiologists use a case investigation form, that provides essential data for every investigation. Dr Roper adds that equally important are those bits of information that do not fit in the form. "What you write in the margins of the form matters a lot. Those bits often reveal the real story."


Dr Roper, WHO epidemiologist in Sierra Leone, on Ebola contact tracing mission.
WHO/D. Licona

11 a.m.: Establishing the facts

Epidemiologists have to sift through inconsistent versions and rumours to get the story right. At the Emergency Response Centre, Dr Roper learned that a person on the contact list was having an engagement party, a risky activity for someone who may have Ebola. But finding out whether the party was happening – or happened – was not a simple task. Here are some examples of the answers Dr Roper got:

Q: Hello! Have you heard about an engagement party involving X?
"They attended an engagement party, yes"
Q: When was that party?
"Well, they were planning the party but it never took place."
Q: Are you sure?
"No."

Q: Hello! Have you heard about an engagement party involving X?
"Yes, yes, but I don’t think they will get married."
Q: Why is that?
"They have only seen each other once."

Katrina and her colleagues continue to investigate to separate "anecdotes" from real, solid evidence. To achieve this, epidemiologists need to ask, ask, and keep asking. By discovering early what actually happened to an infected patient, the investigation teams can save lives of those who are potentially at risk.


Dr Roper, WHO epidemiologist, explains the risks of touching dead bodies (Ebola, Sierra Leone)
WHO/D. Licona

1 p.m.: Warning about risks of touching dead bodies

As the day goes on, there are new and urgent alerts to address. In the community of Kroo Bay, Katrina responds to a call from a district surveillance officer. Despite efforts have been made to raise community awareness of the risks posed by touching dead bodies, 2 dead bodies have been moved by people who did not wait for the safe burial team.

Anyone who has died of Ebola is still highly infectious, and touching dead bodies can put many people at risk of infection. In the photo, Dr Roper explains the importance of calling specialized teams to handle dead bodies.


Dr Roper, WHO epidemiologist, visits a family listed as Ebola contacts, isolated for 21 days, Sierra Leone
WHO/D. Licona

3 p.m.: Explaining the need to remain vigilant

After dealing with the unsafe removal of the dead bodies, Dr Roper takes the opportunity to visit a family in the same neighbourhood who have been listed as contacts of a person confirmed to have Ebola virus disease. People who are contacts are placed under isolation for 21 days and a team of contact tracers visit them every day for those 3 weeks to see if they develop symptoms.

"If tomorrow no one presents symptoms, the isolation time will be over and you will be able to go back to your normal activities", Dr Roper tells them. They smile when they hear the news. She also reminds them of the need to remain vigilant until the outbreak comes to an end.


Dr Roper, WHO epidemiologist, visits communities in Freetown, Sierra Leone, during the Ebola outbreak.
WHO/D. Licona

5 p.m.: It is not over yet

After spending all day investigating, Dr Roper will head back to the office to enter all the information she has collected into a database. Data managers will then ensure all the necessary details are there so the information can be collated and shared to give a picture of what is happening in the outbreak.

Tomorrow, the next day and the day after, people like Dr Roper will continue to walk the streets and alleys, talking to the people and investigating every case until there is no more Ebola virus to chase.