An employee of Zurich's public transport operator Verkehrsbetriebe Zuerich (VBZ) shows how to wear a protective face mask after handing them out to passengers, as a measure against the coronavirus disease (COVID-19), at a tram stop at Bellevue square in Zurich, Switzerland May 19, 2020. REUTERS/Arnd Wiegmann

An employee of Zurich?s public transport operator Verkehrsbetriebe Zuerich (VBZ) hands out protective face masks to passengers, as a measure against the coronavirus disease (COVID-19), at a tram stop at Bellevue square in Zurich, Switzerland May 19, 2020. REUTERS/Arnd Wiegmann

An employee of Zurich’s public transport operator Verkehrsbetriebe Zuerich (VBZ) hands out protective face masks to passengers, as a measure against the coronavirus disease (COVID-19), at a tram stop at Bellevue square in Zurich, Switzerland May 19, 2020. REUTERS/Arnd Wiegmann

A woman wearing a face mask waits for a tram in Manchester, following the outbreak of the coronavirus disease (COVID-19), Manchester, Britain, May 18, 2020. REUTERS/Phil Noble

A woman wearing a face mask crosses a tram line in Manchester city centre, following the outbreak of the coronavirus disease (COVID-19), Manchester, Britain May 18, 2020. REUTERS/Phil Noble

A worker crosses a tram line in Manchester city centre, following the outbreak of the coronavirus disease (COVID-19), Manchester, Britain May 18, 2020. REUTERS/Phil Noble

A man is seen on a tram in Manchester city centre, following the outbreak of the coronavirus disease (COVID-19), Manchester, Britain May 18, 2020. REUTERS/Phil Noble

A passenger wears a protective mask as he sits in a tram of public transport operator Verkehrsbetriebe Zurich (VBZ) as Switzerland eases the lockdown measures during the coronavirus disease (COVID-19) outbreak, in Zurich, Switzerland May 11, 2020. REUTERS/Arnd Wiegmann

A passenger wears a protective mask as he sits in a tram of public transport operator Verkehrsbetriebe Zurich (VBZ) as Switzerland eases the lockdown measures during the coronavirus disease (COVID-19) outbreak, in Zurich, Switzerland May 11, 2020. REUTERS/Arnd Wiegmann

Some people wear protective masks as they wait at a tram stop as Switzerland eases the lockdown measures during the coronavirus disease (COVID-19) outbreak, in Zurich, Switzerland May 11, 2020. REUTERS/Arnd Wiegmann

People wait to board a tram in Manchester city centre following the outbreak of the coronavirus disease (COVID-19), Manchester, Britain May 11, 2020. REUTERS/Phil Noble

A protection mask is added on a tram of public transport operator Verkehrsbetriebe Zurich (VBZ), as the spread of the coronavirus disease (COVID-19) continues, in Zurich, Switzerland May 8, 2020. REUTERS/Arnd Wiegmann

"Lead by example" is written on a protection mask added on a tram of public transport operator Verkehrsbetriebe Zurich (VBZ), as the spread of the coronavirus disease (COVID-19) continues, in Zurich, Switzerland May 8, 2020. REUTERS/Arnd Wiegmann

A protection mask is added on a tram of public transport operator Verkehrsbetriebe Zurich (VBZ) driving in front of the Grossmuenster church, as the spread of the coronavirus disease (COVID-19) continues, in Zurich, Switzerland May 8, 2020. REUTERS/Arnd Wiegmann

A tram platform is seen empty in Manchester, following the outbreak of the coronavirus disease (COVID-19), Manchester, Britain, May 4, 2020. REUTERS/Phil Noble

A passenger wearing a protective face mask is seen in a tram on the first day of the easing of lockdown measures, during the outbreak of the coronavirus disease (COVID-19), in Brussels, Belgium, May 4, 2020. REUTERS/Yves Herman

A woman wearing a protective mask rides a tram amid the coronavirus disease (COVID-19) outbreak in Brussels, Belgium April 28, 2020. From May 4, adults and children aged 12 or above will have to wear masks on public transport in Belgium. REUTERS/Francois Lenoir

A woman wearing a glove sits in front of social distancing signs as she rides a tram amid the coronavirus disease (COVID-19) outbreak in Brussels, Belgium April 28, 2020. From May 4, adults and children aged 12 or above will have to wear masks on public transport in Belgium. REUTERS/Francois Lenoir

A woman wearing a protective mask sits next to social distancing signs as she rides a tram amid the coronavirus disease (COVID-19) outbreak in Brussels, Belgium April 28, 2020. From May 4, adults and children aged 12 or above will have to wear masks on public transport in Belgium. REUTERS/Francois Lenoir

A woman wearing a protective mask and gloves rides a tram amid the coronavirus disease (COVID-19) outbreak in Brussels, Belgium April 28, 2020. From May 4, adults and children aged 12 or above will have to wear masks on public transport in Belgium. REUTERS/Francois Lenoir

Workers wearing protective gear fix a tram line, as the spread of the coronavirus disease (COVID-19) continues, in Beijing, China, April 24, 2020. REUTERS/Thomas Peter

A woman with a protective mask rides a tram during the global coronavirus disease (COVID-19) outbreak in Vienna, Austria, April 20, 2020. REUTERS/Lisi Niesner

A man with a protective mask rides a tram past pedestrians during the global coronavirus disease (COVID-19) outbreak in Vienna, Austria, April 20, 2020. REUTERS/Lisi Niesner

People wearing protective face masks line up at a safe social distance as they wait for a tram at a public transport stop during the coronavirus disease (COVID-19) outbreak in central Kiev, Ukraine April 10, 2020. REUTERS/Gleb Garanich

People wearing protective face masks line up at a safe social distance as they wait for a tram at a public transport stop during the coronavirus disease (COVID-19) outbreak in central Kiev, Ukraine April 10, 2020. REUTERS/Gleb Garanich

People wearing protective face masks are seen in a tram at a public transport stop during the coronavirus disease (COVID-19) outbreak in central Kiev, Ukraine April 10, 2020. REUTERS/Gleb Garanich

A woman wearing protective mask and gloves goes past a tram, as the spread of coronavirus disease (COVID-19) continues, in Milan, Italy April 4, 2020. REUTERS/Daniele Mascolo

A man wearing a protective face mask drives a tram, as the spread of coronavirus disease (COVID-19) continues, in Milan, Italy April 4, 2020. REUTERS/Daniele Mascolo

A woman waits for the tram in Alfama neighbourhood, following the coronavirus disease (COVID-19) outbreak, in Lisbon, Portugal April 2, 2020. REUTERS/Rafael Marchante

A man travels in an almost empty tram wagon during a workday following the implementation of stricter social-distancing and self-isolation rules to limit the spread of the coronavirus disease (COVID-19) in Sydney, Australia, March 31, 2020. REUTERS/Loren Elliott

A combination photo shows tourists waiting for a tram at Comercio square in downtown Lisbon, Portugal August 17, 2018 (top photo) and a bus stop next to Rua Augusta's Arch pictured during partial lockdown as part of state of emergency to combat the coronavirus disease (COVID-19) outbreak in Lisbon, Portugal March 30, 2020. REUTERS/Rafael Marchante

Homeless people sleep at a tram station during a nationwide lockdown to contain the spread of the coronavirus disease (COVID-19), in Piraeus, Greece, March 30, 2020. REUTERS/Alkis Konstantinidis

A man wears a protective mask as he waits for the tram in Frankfurt, Germany, March 26, 2020, as the spread of the coronavirus disease (COVID-19) continues. REUTERS/Kai Pfaffenbach

Trams move on tracks along the street, as the spread of the coronavirus disease (COVID-19) continues, in Lisbon, Portugal March 24, 2020. REUTERS/Rafael Marchante

A woman wears a protective face mask as she waits for a tram in Manchester, as the spread of the coronavirus disease (COVID-19) continues, in Manchester, Britain, March 24, 2020. REUTERS/Phil Noble

A general view shows a closed tram station, following the spread of the coronavirus disease (COVID-19), in Algiers, Algeria March 22, 2020. REUTERS/Ramzi Boudina

A worker wearing a protective suit disinfects a tram, following the outbreak of coronavirus disease (COVID-19), in Casablanca, Morocco March 20, 2020. REUTERS/Youssef Boudlal

A worker wearing a protective suit disinfects a tram, following the outbreak of coronavirus disease (COVID-19), in Casablanca, Morocco March 20, 2020. REUTERS/Youssef Boudlal

A worker wearing a protective suit disinfects a tram, following the outbreak of coronavirus disease (COVID-19), in Casablanca, Morocco March 20, 2020. REUTERS/Youssef Boudlal

A worker wearing a protective suit disinfects a tram, following the outbreak of coronavirus disease (COVID-19), in Casablanca, Morocco March 20, 2020. REUTERS/Youssef Boudlal

A worker wearing a protective suit disinfects a tram, following the outbreak of coronavirus disease (COVID-19), in Casablanca, Morocco March 20, 2020. REUTERS/Youssef Boudlal

A tram is pictured at an empty street as the spread of the coronavirus disease (COVID-19) continues in downtown Lisbon, Portugal March 20, 2020. REUTERS/Rafael Marchante

A municipality worker sprays disinfectant over a tram to prevent the spread of coronavirus disease (COVID-19) in central Istanbul, Turkey, March 18, 2020. REUTERS/Kemal Aslan

A commuter covering his mouth with a scarf rides a tram as Prague City Hall bans all passengers without face protection from the public transport to slow the spread of the new coronavirus disease (COVID-19), in Prague, Czech Republic, March 17, 2020. REUTERS/David W Cerny

An advertising reading " We take care of your Health" is seen on a Public Transport Tram at Alexanderplatz, as the spread of the coronavirus disease (COVID-19) continues, in Berlin, Germany March 17, 2020. REUTERS/Michele Tantussi

A woman is pictured wearing a mask as she walks next to a tram in downtown Lisbon, Portugal March 16, 2020. REUTERS/Rafael Marchante

A man wears a protective mask as he waits for a tram in downtown Zagreb, Croatia, March 15, 2020. REUTERS/Antonio Bronic

A tram crosses a virtually deserted street, amidst concerns over Spain's coronavirus outbreak, in the Basque city of Vitoria, Spain, March 14, 2020. REUTERS/Vincent West

A woman waits for a tram, amidst concerns over Spain's coronavirus outbreak, in the Basque city of Vitoria, Spain, March 14, 2020. REUTERS/Vincent West

A driver of tram wears a protective mask on the fourth day of an unprecedented lockdown across of all Italy imposed to slow the outbreak of coronavirus, in Milan, Italy, March 13, 2020. REUTERS/Daniele Mascolo

A driver of tram wears a protective mask on the fourth day of an unprecedented lockdown across of all Italy imposed to slow the outbreak of coronavirus, in Milan, Italy, March 13, 2020. REUTERS/Daniele Mascolo

Soccer Football - Europa League - Round of 16 First Leg - Inter Milan v Getafe Match Postponed - San Siro, Milan, Italy - March 12, 2020 General view of a passenger on a tram wearing a face mask outside the stadium after the match is postponed REUTERS/Daniele Mascolo

Soccer Football - Europa League - Round of 16 First Leg - Inter Milan v Getafe Match Postponed - San Siro, Milan, Italy - March 12, 2020 General view of the stadium seen from inside an empty tram after the match is postponed REUTERS/Daniele Mascolo

Workers in protective suits prepare to disinfect a tram due to coronavirus disease (COVID-19) concerns in Prague, Czech Republic, March 12, 2020. REUTERS/David W Cerny

A worker in a protective suit disinfects a tram due to coronavirus disease (COVID-19) concerns in Prague, Czech Republic, March 12, 2020. REUTERS/David W Cerny

A worker in a protective suit disinfects a tram due to coronavirus disease (COVID-19) concerns in Prague, Czech Republic, March 12, 2020. REUTERS/David W Cerny

A worker in a protective suit disinfects a tram due to coronavirus disease (COVID-19) concerns in Prague, Czech Republic, March 12, 2020. REUTERS/David W Cerny

A worker in a protective suit disinfects a tram due to coronavirus disease (COVID-19) concerns in Prague, Czech Republic, March 12, 2020. REUTERS/David W Cerny

A worker in a protective suit disinfects a tram due to coronavirus disease (COVID-19) concerns in Prague, Czech Republic, March 12, 2020. REUTERS/David W Cerny

Workers in protective suits prepare to disinfect a tram due to coronavirus disease (COVID-19) concerns in Prague, Czech Republic, March 12, 2020. REUTERS/David W Cerny