Employees of Kando, a wastewater management technology firm, demonstrate a project of sewer surveillance which they say aims to pinpoint unknown outbreaks of coronavirus disease (COVID-19) by identifying traces of the virus in the sewage system, in Ashkelon, southern Israel July 30, 2020. REUTERS/Amir Cohen?

Employees of Kando, a wastewater management technology firm, demonstrate a project of sewer surveillance which they say aims to pinpoint unknown outbreaks of coronavirus disease (COVID-19) by identifying traces of the virus in the sewage system, in Ashkelon, southern Israel July 30, 2020. REUTERS/Amir Cohen?

An employee of Kando, a wastewater management technology firm, demonstrates a project of sewer surveillance which they say aims to pinpoint unknown outbreaks of coronavirus disease (COVID-19) by identifying traces of the virus in the sewage system, in Ashkelon, southern Israel July 30, 2020. REUTERS/Amir Cohen

Employees of Kando, a wastewater management technology firm, demonstrate a project of sewer surveillance which they say aims to pinpoint unknown outbreaks of coronavirus disease (COVID-19) by identifying traces of the virus in the sewage system, in Ashkelon, southern Israel July 30, 2020. REUTERS/Amir Cohen

Andre Blaise Essama, a Cameroonian activist who wants to purge his country of colonial-era symbols, is pictured in front of a statue of the unknown soldier, erected in memory of French soldiers, sailors and allies in Douala, Cameroon July 2, 2020. Picture taken July 2, 2020. REUTERS/Josiane Kouagheu

Andre Blaise Essama, a Cameroonian activist who wants to purge his country of colonial-era symbols, is pictured in front of a statue of the unknown soldier, erected in memory of French soldiers, sailors and allies in Douala, Cameroon July 2, 2020. Picture taken July 2, 2020. REUTERS/Josiane Kouagheu

Andre Blaise Essama, a Cameroonian activist who wants to purge his country of colonial-era symbols, is pictured in front of a statue of the unknown soldier, erected in memory of French soldiers, sailors and allies, in Douala, Cameroon July 2, 2020. Picture taken July 2, 2020. REUTERS/Josiane Kouagheu

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Alexey Filippov via REUTERS

Russian President Vladimir Putin, Moldovan President Igor Dodon, Uzbek President Shavkat Mirziyoyev and Kazakh President Kassym-Jomart Tokayev take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Alexey Filippov via REUTERS

Uzbek President Shavkat Mirziyoyev and Tajik President Emomali Rahmon take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Grigory Sysoev via REUTERS

Heads of states, including Russian President Vladimir Putin and President of Moldova Igor Dodon, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Grigory Sysoev via REUTERS

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Grigory Sysoev via REUTERS

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Grigory Sysoev via REUTERS

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Alexey Filippov via REUTERS

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Alexey Filippov via REUTERS

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Alexey Filippov via REUTERS

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Alexey Filippov via REUTERS

Russian President Vladimir Putin shows the way to Belarusian President Alexander Lukashenko, leader of Georgian breakaway region of Abkhazia Aslan Bzhania, Moldovan President Igor Dodon and Tajik President Emomali Rahmon during a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Grigory Sysoev via REUTERS

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Grigory Sysoev via REUTERS

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Grigory Sysoev via REUTERS

Heads of states, including Russian President Vladimir Putin, take part in a flower-laying ceremony at the Tomb of the Unknown Soldier after the Victory Day Parade in Moscow, Russia, June 24, 2020. The military parade, marking the 75th anniversary of the victory over Nazi Germany in World War Two, was scheduled for May 9 but postponed due to the outbreak of the coronavirus disease (COVID-19). Host photo agency/Grigory Sysoev via REUTERS

A couple is seen during a burial of a person, who died of unknown reasons during the outbreak of the coronavirus disease (COVID-19), at Sao Francisco Xavier cemetery in Rio de Janeiro. Brazil, May 1, 2020. Picture taken May 1, 2020. REUTERS/Ian Cheibub

Gravediggers work in a burial of a person, who died of unknown reasons during the outbreak of the coronavirus disease (COVID-19), at Sao Francisco Xavier cemetery in Rio de Janeiro. Brazil, April 6, 2020. Picture taken April 6, 2020. REUTERS/Ian Cheibub

Worshippers of the African-Brazilian Candomble religion attend a burial of a person, who died of unknown reasons during the outbreak of the coronavirus disease (COVID-19), at Sao Francisco Xavier cemetery in Rio de Janeiro. Brazil, April 23, 2020. Picture taken April 23, 2020. REUTERS/Ian Cheibub

Gravediggers work in a burial of a person, who died of unknown reasons during the outbreak of the coronavirus disease (COVID-19), at Sao Francisco Xavier cemetery in Rio de Janeiro. Brazil, May 3, 2020. Picture taken May 3, 2020. REUTERS/Ian Cheibub

Gravediggers work in a burial of a person, who died of unknown reasons during the outbreak of the coronavirus disease (COVID-19), at Sao Francisco Xavier cemetery in Rio de Janeiro. Brazil, April 6, 2020. Picture taken April 6, 2020. REUTERS/Ian Cheibub

Worshippers of the African-Brazilian religion attend a burial of a person, who died of unknown reasons during the outbreak of the coronavirus disease (COVID-19), at Sao Francisco Xavier cemetery in Rio de Janeiro. Brazil, May 1, 2020. Picture taken May 1, 2020. REUTERS/Ian Cheibub

Worshippers of the African-Brazilian Candomble religion attend a burial of a person, who died of unknown reasons during the outbreak of the coronavirus disease (COVID-19), at Sao Francisco Xavier cemetery in Rio de Janeiro. Brazil, April 23, 2020. Picture taken April 23, 2020. REUTERS/Ian Cheibub

A worshipper of the African-Brazilian Candomble religion attends a burial of a person, who died of unknown reasons during the outbreak of the coronavirus disease (COVID-19), at Sao Francisco Xavier cemetery in Rio de Janeiro. Brazil, April 23, 2020. Picture taken April 23, 2020. REUTERS/Ian Cheibub

A gravedigger walks by Sao Francisco Xavier cemetery after the burial of a person, who died of unknown reasons, during the outbreak of the coronavirus disease (COVID-19), in Rio de Janeiro, Brazil, April 10, 2020. Picture taken April 10, 2020. REUTERS/Ian Cheibub

A woman is comforted by a friend after a relative was gunned down by unknown assailants outside a garage, in Mexico City, Mexico February 12, 2020. Picture taken February 12, 2020. REUTERS/Luis Cortes

A forensic technician and a police officer work at a crime scene stand where unknown assailants attacked a vehicle, in Ecatepec de Morelos, on the outskirts of Mexico City, Mexico April 25, 2020. Picture taken April 25, 2020. REUTERS/Luis Cortes

Blood stains are pictured on the wheel of a truck following an attack by unknown assailants in Mexico City, Mexico January 22, 2020. Picture taken January 22, 2020. REUTERS/Luis Cortes

A police investigator takes notes at a crime scene where a man was gunned down by unknown assailants outside a garage, in Mexico City, Mexico February 12, 2020. Picture taken February 12, 2020. REUTERS/Luis Cortes

A bullet impact is pictured at the window of a truck following an attack by unknown assailants in Mexico City, Mexico January 22, 2020. Picture taken January 22, 2020. REUTERS/Luis Cortes

A police investigator works at a crime scene where a man was gunned down by unknown assailants, in Mexico City, Mexico April 15, 2020. Picture taken April 15, 2020. REUTERS/Luis Cortes

A forensic technician and a police officer stand by the body of a man at a crime scene where unknown assailants attacked a vehicle, in Ecatepec de Morelos, on the outskirts of Mexico City, Mexico April 25, 2020. Picture taken April 25, 2020. REUTERS/Luis Cortes

A forensic technician works at a crime scene where unknown assailants attacked a vehicle, in Ecatepec de Morelos, on the outskirts of Mexico City, Mexico April 25, 2020. Picture taken April 25, 2020. REUTERS/Luis Cortes

A vandalized monument to Unknown Confederate Dead is seen in Oakland Cemetery as protesters rally against racial inequality in Atlanta, Georgia, U.S. June 10, 2020. REUTERS/Dustin Chambers

Honour guards march to the Tomb of the Unknown Soldier as people enjoy the sunny weather in a park on the first day after a lockdown designed to curb the spread of the coronavirus disease (COVID-19) was lifted in Moscow, Russia June 9, 2020. REUTERS/Shamil Zhumatov

Residents observe a crime scene where unknown assailants killed four people, in Tegucigalpa, Honduras June 5, 2020. REUTERS/Jorge Cabrera

A woman reacts at a crime scene where unknown assailants killed four people, in Tegucigalpa, Honduras June 5, 2020. REUTERS/Jorge Cabrera

A woman reacts at a crime scene where unknown assailants killed four people, in Tegucigalpa, Honduras June 5, 2020. REUTERS/Jorge Cabrera

A forensic technician works at a crime scene where unknown assailants killed four people, in Tegucigalpa, Honduras June 5, 2020. REUTERS/Jorge Cabrera

Police officers and forensic technicians work at a crime scene where unknown assailants killed four people, in Tegucigalpa, Honduras June 5, 2020. REUTERS/Jorge Cabrera

A general view shows police officers and forensic technicians as they work at a crime scene where unknown assailants killed four people, in Tegucigalpa, Honduras June 5, 2020. REUTERS/Jorge Cabrera

An activist holds a picture of Wanchalearm Satsaksit, 37, a Thai political activist who was abducted by unknown gunmen in front of his Phnom Penh apartment, during a protest for his disappearance in Bangkok, Thailand, June 5, 2020. REUTERS/Athit Perawongmetha

An activist holds a picture of Wanchalearm Satsaksit, 37, a Thai political activist who was abducted by unknown gunmen in front of his Phnom Penh apartment, during a protest for his disappearance in Bangkok, Thailand, June 5, 2020. REUTERS/Athit Perawongmetha

An activist holds a picture of Wanchalearm Satsaksit, 37, a Thai political activist who was abducted by unknown gunmen in front of his Phnom Penh apartment, during a protest for his disappearance in Bangkok, Thailand, June 5, 2020. REUTERS/Athit Perawongmetha

Members of the media take photo of a picture of Wanchalearm Satsaksit, 37, a Thai political activist who was abducted by unknown gunmen in front of his Phnom Penh apartment, during a protest for his disappearance in Bangkok, Thailand, June 5, 2020. REUTERS/Athit Perawongmetha

An activist lies flowers in front of a picture of Wanchalearm Satsaksit, 37, a Thai political activist who was abducted by unknown gunmen in front of his Phnom Penh apartment, during a protest for his disappearance in Bangkok, Thailand, June 5, 2020. REUTERS/Athit Perawongmetha

An activist lies flowers in front of a picture of Wanchalearm Satsaksit, 37, a Thai political activist who was abducted by unknown gunmen in front of his Phnom Penh apartment, in Bangkok, Thailand, June 5, 2020. REUTERS/Athit Perawongmetha

A child helps a man to fill plastic containers with water from an unknown source in the low-income neighbourhood of Petare amid the coronavirus disease (COVID-19) outbreak in Caracas, Venezuela June 3, 2020. Picture taken June 3, 2020. REUTERS/Manaure Quintero

People extract water from an unknown source in the low-income neighbourhood of Petare amid the coronavirus disease (COVID-19) outbreak in Caracas, Venezuela June 3, 2020. Picture taken June 3, 2020. REUTERS/Manaure Quintero

People extract water from an unknown source in the low-income neighbourhood of Petare amid the coronavirus disease (COVID-19) outbreak in Caracas, Venezuela June 3, 2020. Picture taken June 3, 2020. REUTERS/Manaure Quintero

A man carries a child over a wheelbarrow near an unknown water source in the low-income neighbourhood of Petare amid the coronavirus disease (COVID-19) outbreak in Caracas, Venezuela June 3, 2020. Picture taken June 3, 2020. REUTERS/Manaure Quintero

People walk with plastic containers near an unknown water source in the low-income neighbourhood of Petare amid the coronavirus disease (COVID-19) outbreak in Caracas, Venezuela June 3, 2020. Picture taken June 3, 2020. REUTERS/Manaure Quintero

People extract water from an unknown source in the low-income neighbourhood of Petare amid the coronavirus disease (COVID-19) outbreak in Caracas, Venezuela June 3, 2020. Picture taken June 3, 2020. REUTERS/Manaure Quintero

Police investigators work at the crime scene where unknown assailants left a bag with human remains, in Valle de Chalco, in the State of Mexico, Mexico June 3, 2020. REUTERS/Luis Cortes

Police investigators work at the crime scene where unknown assailants left a bag with human remains as a Mexican National Guard soldier stands guard, in Valle de Chalco, in the State of Mexico, Mexico June 3, 2020. REUTERS/Luis Cortes