A COVID-19 safety sign is posted near the Vietnam Memorial in Washington, U.S., May 25, 2020. REUTERS/Erin Scott

Masked visitors to the Vietnam Memorial pay respects in Washington, U.S., May 25, 2020. REUTERS/Erin Scott

A visitor passes a COVID-19 safety sign arriving at the the Vietnam Veterans Memorial wearing a protective mask in the midst of the coronavirus disease (COVID-19) pandemic, as people commemorate the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

U.S. Army Vietnam veteran Brent Gulick touches a name of one of the fallen on the memorial wall of the Vietnam Veterans Memorial, as he wears a protective mask in the midst of the coronavirus disease (COVID-19) pandemic, as people commemorate the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

Members of the U.S. military, veterans and members of the public visit the Vietnam Veterans Memorial in the midst of the coronavirus disease (COVID-19) pandemic while commemorating the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

A visitor reads the names of the fallen on the Vietnam Veterans Memorial in the midst of the coronavirus disease (COVID-19) pandemic as people commemorate the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

A veteran and a person accompanying him embrace while visiting the wall of the Vietnam Veterans Memorial as people commemorate the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

Members of the public and veterans visit the Vietnam Veterans Memorial, many wearing protective face masks in the midst of the coronavirus disease (COVID-19) pandemic, as people commemorate the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

U.S. veterans, some wearing protective face masks in the midst of the coronavirus disease (COVID-19) pandemic, carry a wreath to the Vietnam Veterans Memorial as people commemorate the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

A family dressed in U.S. Army shirts joins veterans and other members of the public in visiting the Vietnam Veterans Memorial in the midst of the coronavirus disease (COVID-19) pandemic while commemorating the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

Flowers draped with two American flags sit at the Vietnam Veterans Memorial in the midst of the coronavirus disease (COVID-19) pandemic during commemorations of the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

U.S. veterans, wearing protective face masks in the midst of the coronavirus disease (COVID-19) pandemic, carry a wreath to the Vietnam Veterans Memorial as people commemorate the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

Flowers draped with two American flags sit at the Vietnam Veterans Memorial in the midst of the coronavirus disease (COVID-19) pandemic during commemorations of the U.S. Memorial Day holiday in Washington, U.S., May 25, 2020. REUTERS/Michael A. McCoy

Traffic jam is seen in morning rush hour after the government eased nationwide lockdown following the coronavirus disease (COVID-19) outbreak in Hanoi, Vietnam May 25, 2020. REUTERS/Kham

Traffic jam is seen in morning rush hour after the government eased nationwide lockdown following the coronavirus disease (COVID-19) outbreak in Hanoi, Vietnam May 25, 2020. REUTERS/Kham

Traffic jam is seen in morning rush hour after the government eased nationwide lockdown following the coronavirus disease (COVID-19) outbreak in Hanoi, Vietnam May 25, 2020. REUTERS/Kham

Traffic jam is seen in morning rush hour after the government eased nationwide lockdown following the coronavirus disease (COVID-19) outbreak in Hanoi, Vietnam May 25, 2020. REUTERS/Kham

Traffic jam is seen in morning rush hour after the government eased nationwide lockdown following the coronavirus disease (COVID-19) outbreak in Hanoi, Vietnam May 25, 2020. REUTERS/Kham

Traffic jam is seen in morning rush hour after the government eased nationwide lockdown following the coronavirus disease (COVID-19) outbreak in Hanoi, Vietnam May 25, 2020. REUTERS/Kham

A sign warns of the coronavirus disease (COVID-19) outbreak at the Vietnam Veterans Memorial in Washington, U.S., May 24, 2020. REUTERS/Joshua Roberts

A man wearing a mask due to the coronavirus disease (COVID-19) outbreak uses a cell phone at the Vietnam Veterans Memorial in Washington, U.S., May 24, 2020. REUTERS/Joshua Roberts

People wearing masks due to the coronavirus disease (COVID-19) outbreak make photographs at the Vietnam Veterans Memorial in Washington, U.S., May 24, 2020. REUTERS/Joshua Roberts

People wearing masks due to the coronavirus disease (COVID-19) outbreak walk at the Vietnam Veterans Memorial in Washington, U.S., May 24, 2020. REUTERS/Joshua Roberts

Vietnam Airlines's cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai attend their wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Vietnam Airlines' cabin attendant Tran Le Duyen is seen at her wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Vietnam Airlines' cabin attendant Tran Le Duyen is seen in her wedding gown after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Vietnam Airlines' cabin attendant Tran Le Duyen poses for a photo with family members at her wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Vietnam Airlines' cabin attendant Tran Le Duyen waits for as her groom, aviation sector businessman Nguyen Van Trai to come up the stairs during their wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which delayed their original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Relatives celebrate with Vietnam Airlines's cabin attendant Tran Le Duyen and air service businessman Nguyen Van Trai during their wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Relatives stand around Vietnam Airlines's cabin attendant Tran Le Duyen and air service businessman Nguyen Van Trai during their wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Relatives attend the wedding party of Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 22, 2020. Picture taken May 22, 2020. REUTERS/Kham

Relatives attend the wedding party of Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 22, 2020. Picture taken May 22, 2020. REUTERS/Kham

Relatives attend the wedding party of Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 22, 2020. Picture taken May 22, 2020. REUTERS/Kham

Relatives drink during the wedding party of Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 22, 2020. Picture taken May 22, 2020. REUTERS/Kham

Relatives attend the wedding party of Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which pushed back the original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai react with their parents during the wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which delayed their original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai kiss during their wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which delayed their original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai are seen with their parents during their wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which delayed their original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai are seen during their wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which delayed their original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Vietnam Airlines' cabin attendant Tran Le Duyen and aviation sector businessman Nguyen Van Trai pour champagne during the wedding ceremony after the Vietnamese government eased the nationwide lockdown for the coronavirus disease (COVID-19) outbreak, which delayed their original wedding date, in Hanoi, Vietnam May 23, 2020. Picture taken May 23, 2020. REUTERS/Kham

Migrants from Vietnam stand at playground inside Principovac camp for migrants near Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

Vietnamese tourists visit Ha Long bay after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Quang Ninh province, Vietnam May 19, 2020. REUTERS/Kham

Junk boats transporting Vietnamese tourists are seen at Ha Long bay after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Quang Ninh province, Vietnam May 19, 2020. REUTERS/Kham

A sunset is seen in a resort after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Phu Quoc island, Vietnam May 8, 2020. Picture taken May 8, 2020. REUTERS/James Pearson

Vietnamese tourists are seen on a junk boat as they visit Ha Long bay after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Quang Ninh province, Vietnam May 19, 2020. REUTERS/Kham

Vietnamese tourists pose for photos on the The Huc bridge at Hoan Kiem lake after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Hanoi, Vietnam May 18, 2020. Picture taken May 18, 2020. REUTERS/Kham

Phu Quoc resort island is seen via the window of an airplane after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, Phu Quoc Island, Vietnam May 8, 2020. Picture taken May 8, 2020. REUTERS/James Pearson

Empty chairs are seen on a beach at Ha Long bay after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Quang Ninh province, Vietnam, May 19, 2020. REUTERS/Kham

Coronavirus awareness banner is seen at a locked tourism port at Ha Long bay after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Quang Ninh province, Vietnam May 19, 2020. REUTERS/Kham

Vietnamese tourists visit Ha Long bay after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Quang Ninh province, Vietnam May 19, 2020. REUTERS/Kham

Vietnamese tourists visit Ha Long bay after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Quang Ninh province, Vietnam, May 19, 2020. REUTERS/Kham

Vietnamese tourists visit Ha Long bay after the Vietnamese government eased the lockdown following the coronavirus disease (COVID-19) outbreak, in Quang Ninh province, Vietnam, May 19, 2020. REUTERS/Kham

Police officers remove barriers as the quarantine is lifted in Dong Cuu village, the last Vietnamese village affected by the coronavirus disease (COVID-19), outside Hanoi, Vietnam May 14, 2020. REUTERS/Kham

A police officer removes barriers as the quarantine is lifted in Dong Cuu village, the last Vietnamese village affected by the coronavirus disease (COVID-19), outside Hanoi, Vietnam May 14, 2020. REUTERS/Kham

Residents celebrate after authorities lifted the quarantine in Dong Cuu village, the last Vietnamese quarantined village affected by the coronavirus disease (COVID-19), outside Hanoi, Vietnam May 14, 2020. REUTERS/Kham

Residents celebrate as the police officers leave, after authorities lifted the quarantine in Dong Cuu village, the last Vietnamese quarantined village affected by the coronavirus disease (COVID-19), outside Hanoi, Vietnam May 14, 2020. REUTERS/Kham

Residents celebrate after authorities lifted the quarantine in Dong Cuu village, the last Vietnamese quarantined village affected by the coronavirus disease (COVID-19), outside Hanoi, Vietnam May 14, 2020. REUTERS/Kham TPX IMAGES OF THE DAY

Police and soldiers remove barriers as the quarantine is lifted in Dong Cuu village, the last Vietnamese village affected by the coronavirus disease (COVID-19), outside Hanoi, Vietnam May 14, 2020. REUTERS/Kham

Residents celebrate after authorities lifted the quarantine in Dong Cuu village, the last Vietnamese quarantined village affected by the coronavirus disease (COVID-19), outside Hanoi, Vietnam May 14, 2020. REUTERS/Kham

Residents celebrate after authorities lifted the quarantine in Dong Cuu village, the last Vietnamese quarantined village affected by the coronavirus disease (COVID-19), outside Hanoi, Vietnam May 14, 2020. REUTERS/Kham