Swabs and air samples taken from London's Tube trains, buses and stations have come back without any traces of COVID, including any of its variants.Heavily monitored public areasThroughout the pandemic, cleanliness and hygiene measures have been considerably reinforced to ensure contaminated surfaces are kept at a strict minimum. Researchers at Imperial College London examined heavily touched areas such as ticket barriers, stop buttons, rails, handles and seats on Tube trains with a machine that drew in 300 litres (about 66 gallons) of air per minute to detect the appearance of the virus. Surprisingly, the results that came back to the team showed that there were no traces of the virus in any of the heavily monitored areas. Needless to say, experts believe that though the lockdown and social distancing measures are a direct result of the lack of appearance of the virus, this does not mean Londoners should let their guard down.Dr David Green, senior research fellow at Imperial, said:As we've moved on, we are much more convinced that the routes of transmission tend to be through the air –through breathing, through being in confined environments, not maintaining social distancing or not wearing masks. If you think about the London Underground environment and other transport networks, they are being cleaned very regularly and very thoroughly at the moment.And added: All of the results have been negative so far, which is very reassuring for everybody travelling. But if we did get a positive result, then we could do further investigations into which particular variant it was. Public must continue respecting restrictionsAs lockdown measures are progressively being loosened, experts wish to remind the general public to continue practicing the safety measures that have been put into place to contain the virus as much as possible. Dr Green explained that: The occupancy level is much lower. And everybody is wearing masks. All of these things will reduce the chances of the virus being spread in these environments.