Wearing the gauntlet: diagnosing Ebola in Sierra Leone
How do you diagnose the Ebola virus in places that until recently had very little healthcare infrastructure? Just behind the frontlines of the Ebola epidemic in Sierra Leone, volunteers are running laboratories diagnosing Ebola cases. In late 2014 two PhD students in Professor Richard Elliott’s group from the MRC-University of Glasgow Centre for Virus Research spent five weeks in Sierra Leone helping to set up an Ebola diagnostic laboratory. Here Gillian Slack and Steve Welch explain their experience.
As virology PhD students with backgrounds in laboratory diagnostics, we both have experience of using blood, urine and saliva samples to diagnose tropical infectious diseases. We wanted to put those skills to good use in Sierra Leone.
We were part of a group of 14 volunteers from the UK travelling to Kerry Town in Sierra Leone where a treatment centre for Ebola patients was being established.
We received intensive training at the Public Health England labs in Porton Down, where they had built a scale replica of the lab we would be using. As well as the training, we also had numerous vaccinations and medical and psychological assessments before we were cleared to deploy.
When we first arrived, after a convoluted series of flights through Belgium, Senegal and Guinea, the location of the lab and hospital was still a building site. But in the space of seven days the team managed to get the lab benches in and set up the major kit. This included the isolators in which lab staff handle samples, and the PCR (polymerase chain reaction) machines to detect viral RNA.
On the first day of opening the laboratory we received over 100 samples to process and test. These were either blood or mouth swab samples from suspected Ebola patients in holding centres throughout western Sierra Leone, or from people that may have died from the infection.
It is important to turn around the analysis of both kinds of samples as quickly as possible. Before a diagnosis is confirmed all suspected cases are cared for on the same ward, so quickly working out who has the virus means they can be isolated, and uninfected people protected.
The results from the mouth swabs are used for epidemiological study to help track the pattern of the epidemic, helping to trace people who may have been in contact with the patient. Moreover they dictate how the bodies of the deceased will be buried, which is important to the families of the victims.
Not long after the diagnostic lab was set up, the adjacent Ebola Treatment Centre (ETC) was also ready to take patients.
If the samples were provided by the ETC, they would be collected throughout the day and carefully delivered to us in the lab from the ‘hot zone’, where the patients are treated, via a special walkway between the two buildings. Community samples are collected by ambulance and then delivered to the lab.
You’ll have seen this on news footage, but when receiving specimens, we all had to wear special personal protective equipment (PPE) to protect us from both the virus and the strong bleach solution we used to disinfect the samples. This means a disposable apron, safety goggles, a facemask and a safety visor. It’s pretty unpleasant wearing it all in the hot afternoon sun in Sierra Leone, where temperatures regularly exceed 35 degrees. However, with Ebola wards all around you, there’s a regular reminder of why you shouldn’t complain.
When samples arrive, the first thing to do is visually inspect them for any leaks or breakages. All samples arrived in three layers of containment ― the primary sample tube, a second larger screw-cap container and lastly a clear zip-lock bag.
To ensure the safety of the people working in the lab and the couriers transporting the samples, any poorly packaged or leaking samples are returned for repackaging. If the samples look okay, the zip-lock bag is opened under a strong bleach solution, which ensures complete decontamination of the secondary container.
Once decontaminated, the samples, still in their primary and secondary containers, are moved into the lab where they are handled inside an isolator. This piece of equipment is a sealed cabinet that works under negative pressure, ensuring no virus particles can escape into the surrounding environment.
All manipulation and pipetting of the samples is carried out using built-in arm-length gauntlets. Only when any virus present is inactivated are samples removed, via a pass box which acts like an airlock.
We used commercial kits to extract virus RNA ― if it was there ― and then used the PCR machine to detect Ebola RNA. In Kerry Town we were receiving samples daily and the PCR machines were in 24-hour use.
When the PCR machines finish their job, two members of staff check and validate by the results ― check and check again. Confirmed results go into a database and are emailed to the centralised Ebola Command Centre in Freetown for dissemination.
This quick turnaround of results is vital, but you have to strike a balance between the drive to work as quickly as possible and the need to generate safe and accurate results. Keeping a cool head is essential.
During our time in Sierra Leone we were invited to attend the release ceremonies of several patients who had recovered from Ebola. These patients had been monitored throughout their care and were only released once the virus could no longer be detected in their blood.
It was incredibly humbling and rewarding to see patients recover and then, most importantly, be reunited with their families. The ceremonies were a strong reminder of why we were there and will always stay with me. It demonstrated to us the important role healthcare workers, treatment centres and diagnostic labs are playing in this epidemic.
Gillian Slack and Steve Welch
The photos in this piece are copyright of Gillian Slack and Steve Welch.