Delta variant threatens to overload Vietnam's healthcare system: experts By Thuy An, Le Phuong  July 3, 2021 | 06:30 pm GMT+7 A medic puts nose swab samples into a tube in HCMC's Binh Tan District, June 22, 2021. Photo by VnExpress/Huu Khoa. The fast spreading Delta strain is responsible for a high number of community infections in Vietnam's ongoing Covid-19 wave, making it hard to control, experts said. Phan Trong Lan, head of Ho Chi Minh City Pasteur Institute, Vietnam's leading epidemiology center, said the Delta variant, or B.1.167.2, first detected in India, has been labeled highly transmissible by the World Health Organization, and able to reduce the efficacy of available Covid-19 vaccines.