How the UK Is Tracing Its First Ebola Diagnosis

​On Monday, the Scottish government confirmed a case of Ebola—the first to be diagnosed in the UK. Now, public health authorities are tracing every person who might have come into contact with the patient on her journey home.

"Contact tracing" is an important step to limit the spread of the virus. The World Health Organisation (WHO) describes it as an "integral component of the overall strategy for controlling an outbreak," as it helps identify and isolate cases early.

It basically means tracking anyone who could have come into contact with the infected person and may therefore be at risk. In this case, it's highly unlikely that a fellow traveller could have been infected; Ebola is not contagious until symptoms are present, and even then you have to have contact with bodily fluids.

Nevertheless, the tracing operation is considerable: A spokesperson for Public Health England (PHE), part of the Department of Health, said this case involved contacting 132 people who were on the same flight as the individual, named as nurse Pauline Cafferkey.

A team of 20 led by scientists from PHE's Field Epidemiology Service are tasked with calling each one of those passengers.

Cafferkey contracted the virus while volunteering in West Africa, and started showing symptoms after flying from Sierra Leone to London's Heathrow via Casablanca in Morocco, then on to Glasgow in Scotland. The flight from Casablanca is PHE's concern; Health Protection Scotland is working on the Glasgow-bound leg of the journey.

"Although the risk of infection to other passengers on the flights is considered extremely low, PHE is involved in contacting 100 passengers on the flight from Casablanca to Heathrow," a PHE spokesperson told me over email. "An additional 32 international passengers are being contacted by international public health authorities."

The UK has seen only one case of Ebola before in aid worker William Pooley, and he was diagnosed in Sierra Leone before being treated in London.

PHE can find out who was on the flight by obtaining the flight manifest, which also gives contact numbers and a seating plan. That last part's important, as PHE has specific guidelines for those seated within two rows of the passenger. It advises the 21 people in the "direct vicinity" to take their temperature twice a day until January 18, and seek further advice if it goes above 37.5 Celsius or they feel unwell.

Other passengers are given "general information and reassurance," along with airline crew and border staff who may have come into contact.

The PHE spokesperson said the agency has now successfully contacted 85 people, which left 15 to go. In general, the biggest challenge of contact tracing is if an airline doesn't have a passenger's contact details, which can occur depending on the booking route. "In this scenario, we work with other booking agents to source the contact details," the spokesperson added.

Contact tracing can be a lot harder in other places, and it's one of the reasons we haven't been able to stop the outbreak yet. WHO guidelines explain that in West Africa, the wide geographical spread of the virus plus a lack of resources made for serious challenges. If tracing contacts of one person when you have a flight manifest is tough enough, imagine getting to grips with the tens of thousands of cases reported in Guinea, Liberia, and Sierra Leone. A flight seating plan is pretty simple to track down, but in other situations it's necessary to identify contacts simply through interviews.

Meanwhile, questions have been raised as to why Cafferkey was able to take a domestic flight after arriving in Heathrow. She told officials she felt unwell, but was able to fly on to Glasgow after her temperature was repeatedly tested and found to be normal. In an interview with Sky News today, Chief Medical Officer Sally Davies told Sky News today the situation had "not been as good as we would all want to see," and that Public Health England would have to make changes when dealing with large groups of passengers at screenings.

The Scottish government writes that "many of those" on the Glasgow flight have already been contacted by Health Protection Scotland.