A man passes a graffiti on a wall during the coronavirus disease (COVID-19) outbreak in Vienna, Austria April 2, 2020.

Residents write words "stay home" with their mobile phones as they stand on the balcony of their apartment block during the lockdown imposed by the Belgian government to slow down the coronavirus disease (COVID-19) spread, in Ruisbroek near Brussels, Belgium April 5, 2020.

A message is seen on the window of a shop in Cambridge Market Square, as the spread of the coronavirus disease (COVID-19) continues, Cambridge, Britain, April 1, 2020.

Men wearing face masks ride past a mural showing a thank you to country's medical workers tackling coronavirus disease (COVID-19) amid its spread, at a road in Depok, south of Jakarta, Indonesia, April 7, 2020.

Social distancing markings are seen on the pavement in Greenwich Park, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 4, 2020.

A cyclist rides past a mural in tribute to the NHS painted by artist Rachel List on the gates of Hope & Anchor pub in Pontefract, as the spread of the coronavirus disease (COVID-19) continues, Pontefract, Britain, April 4, 2020.

A man wearing a face mask walks past a graffiti message to the NHS written on the wall of a residential building, as the spread of the coronavirus disease (COVID-19) continues, in Hackney, London, Britain April 2, 2020.

A message reading "Together we can all win" is displayed at the Tokyo Skytree after Japan's Prime Minister Shinzo Abe declared a state of emergency to fight the coronavirus disease (COVID-19), in Tokyo, Japan April 7, 2020.

Dance instructor Morgan Jenkins makes a video in front of a mural during the global outbreak of the coronavirus disease (COVID-19), in Los Angeles, California, U.S., April 3, 2020.

A woman walks her dog in front of a social distancing message after California issued a stay-at-home order as the spread of the coronavirus disease (COVID-19) continues, in Los Angeles, California, U.S., April 3, 2020.

A man walks beneath a billboard during the 21-day nationwide lockdown aimed at limiting the spread of coronavirus disease (COVID-19) in central Cape Town, South Africa, April 6, 2020.

A general view of a sign with a message in tribute to key workers as media wait outside St Thomas' Hospital, London, Britain, April 7, 2020.

A message of support to the NHS and key workers is seen outside a house in West London as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 2, 2020.

Messages are pictured on the happiness board in the intensive care unit (ICU) in a hospital during the coronavirus disease (COVID-19) outbreak in Payerne, Switzerland, April 6, 2020. Laurent Gillieron/Pool via REUTERS

A person walks by a sign on a freeway overpass during the global outbreak of the coronavirus disease (COVID-19), in Los Angeles, California, U.S., April 3, 2020.

Artist Rachel List paints a mural, as the spread of the coronavirus disease (COVID-19) continues, in Pontefract, Britain, April 6, 2020.

Artist David "S.I.D." Perez paints a graffiti of a cashier to pay tribute to essential workers during the coronavirus disease (COVID-19) outbreak in Gland, Switzerland, April 5, 2020.

People walk past a message on a billboard in West London, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 1, 2020.

A man wearing a face mask walks past a graffiti, as the spread of the coronavirus disease (COVID-19) continues, in Milan, Italy April 6, 2020.

A woman wearing a face mask signs her autograph on the legendary graffiti-covered John Lennon Wall as the spread of the coronavirus disease (COVID-19) continues in Prague, Czech Republic, April 6, 2020.

A mural showing medical personel wearing protective masks is seen painted on a wall of a building following the coronavirus disease (COVID-19) outbreak in Warsaw, Poland, April 1, 2020. Slawomir Kaminski/Agencja Gazeta via REUTERS

People applaud from their balconies during the Clap for our Carers campaign in support of NHS as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 2, 2020.

A woman walks past graffiti stating "Wash Your Hands" in London, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 3, 2020.

Lilly Davenport poses for her dad infront of a mural in tribute to the NHS painted by artist Rachel List on the wall of the Horse Vaults pub in Pontefract, as the spread of the coronavirus disease (COVID-19) continues, Pontefract, Britain, April 4, 2020.

A person walks past a message on a billboard in West London, as the spread of the coronavirus disease (COVID-19) continues, London, Britain, April 1, 2020.

People walk past a message supporting the NHS as the spread of the coronavirus disease (COVID-19) continues, Liverpool, Britain, April 2, 2020.

A woman wearing a protective mask stands next to a closed ice cream kiosk with a graffiti during lockdown, amid the coronavirus disease (COVID-19) outbreak, in Madrid, Spain April 5, 2020. Graffiti reads: "Europe needed a scare".

Swiss army soldier Arthur waves next to a heart shape made of flowers to thank medical workers on the ground of a hospital during the coronavirus disease (COVID-19) outbreak in Payerne, Switzerland, April 6, 2020. The message reads "for you". Laurent Gillieron/Pool via REUTERS