Researchers from Imperial College London are working with Transport for London (TfL) to regularly test the UK capital’s transport network for the virus that causes Covid-19.
The scientists, from Imperial’s Environmental Research Group and the Barclay Laboratory, conduct monthly sampling on the tube and bus network and analyse for the SARS-CoV-2 virus.
Samples are taken of the particles in the air to detect possible viral particles that network users breathe out.
Surfaces people regularly touch, such as oyster card readers, ticket machines, escalator handrails and buttons, are also swabbed by the team.
In total, the team stops at underground stations for an hour at a time, and takes samples at two stations, on one tube line, and one bus.
The samples are delivered on the same day to the lab of Professor Wendy Barclay where they are analysed using polymerase chain reaction, which rapidly amplifies a genetic material called RNA, making it possible to detect genetic sequences specific to the virus.
All samples are placed into virus transportation medium immediately after they are collected from the transport network, to stop the viral RNA becoming damaged.
Dr David Green, head of the Aerosol Science Team at Imperial, said: “We have been taking samples on the TfL network for a number of years as part of an international study called MetaSUB.
“This aims to improve the understanding of biological material such as bacteria and fungi found in the subway systems by looking at the DNA found there.
“The study involves scientists from cities with subway systems like Boston, Paris, Sydney and Shanghai taking swabs and air samples. It is a very similar process to look for viral RNA.”
Dr Green added: “In the same way that a swab is used to take a Covid-19 test in the nose and throat, we just use a flocked swab to detect viruses on surfaces such as handrails.”
So far Imperial researchers have found no trace of the virus on the TfL network.