One in three people infected with COVID are unware they have the virus. Face coverings have been compulsory since last June on Tubes and buses, and many schools now insist on parents wearing masks when collecting children.
Khan said, "I have stopped walking my dog in the park because it's so busy." Instead, he said he takes his dog Luna for walks on the pavement.
Meanwhile, the mayor also revealed that the number of London bus drivers to die with COVID had increased to 38. More than 60 London transport staff have died in the pandemic.
Khan said bus driver deaths had previously been investigated by University College London at the request of Transport for London.
England is currently under the third national lockdown since the outbreak of the pandemic in the country. Similar restriction measures are also in place in Scotland, Wales and Northern Ireland.
To bring life back to normal, countries such as Britain, China, Germany, Russia and the United States have been racing against time to roll out coronavirus vaccines.