After spending around a month with no new community transmission, on April 27 Vietnam saw its streak broken after a hotel employee in the northern Yen Bai Province got infected from a group of Indian experts quarantined at the hotel.

Two days later, six local cases were recorded in northern Ha Nam Province, stemming from a man who finished his mandatory 14-day quarantine period after returning from Japan, but neglected self-isolation protocols and passed on the virus.

In the coming days, multiple coronavirus outbreaks were recorded nationwide in different locations, following a four-day Reunification Day holiday that saw tourism sites jam-packed with people. As of Saturday, the spark of infection has ballooned into 176 community cases recorded in 19 cities and provinces, forcing lockdowns on several places across the country.

Even some of the nation’s major hospitals, supposed to be at the frontline of the Covid-19 fight, did not emerge unscathed. Hanoi’s National Hospital for Tropical Diseases, the capital’s main facility for Covid-19 treatment, has been locked down as it became a coronavirus hotspot causing dozens of infections in various northern localities.

"The stronghold has now been breached," said Health Minister Nguyen Thanh Long, referring to the hospital.

The capital's K Hospital, a top cancer treatment facility, was also locked down Friday as a new coronavirus hotspot.

Vietnam’s fourth coronavirus wave has shown marked differences compared with previous waves in Da Nang last year or Hai Duong Province earlier this year, being its simultaneous presence in different localities, the existence of different variants, difficulties in tracking down transmission sources and cases being revealed only after quarantine periods end, experts said.

Multiple outbreaks

Nguyen Van Kinh, chairman of the specialist council for Covid-19 treatment, said previous coronavirus waves were sparked as one hotspot spread to different locations. For example, the Da Nang outbreak last year had the Da Nang Hospital as its epicenter, while the Hai Duong outbreak earlier this year had the Poyun industrial area as its epicenter, he explained.

But this time things are different: multiple outbreaks have been observed across different locations within a short time frame. There's the Ha Nam Province outbreak stemming from a man who finished his mandatory quarantine period after returning from Japan, but tested positive anyway and passed on the disease to other cases in localities like Hanoi, HCMC and Hung Yen. Then there’s the outbreak in Vinh Phuc Province associated with a group of Chinese experts who also finished quarantine before their tests returned positive, and the Yen Bai Province outbreak where a group of Indian experts stayed at a local hotel and tested positive. The latest outbreaks include those at the National Hospital for Tropical Diseases, which have proved to be remarkably contagious as it had managed to spread to so many other localities.

"This coronavirus wave is much more complex with so many outbreaks involved, forcing all provinces to ramp up their coronavirus prevention measures," said Kinh.

Variants of concerns

Genetic sequencing has revealed the existence of several coronavirus variants among cases in the new wave, most notably a variant carrying double mutations with origins from India: B.1.617.

This variant, making its first appearance in Vietnam, contains two key mutations called E484Q and L452R, which have been found separately in other variants but not together in a single strain. These mutations have been shown to make the virus more transmissible and to be less susceptible to neutralizing antibodies, experts said.

The variant has been found among patients in outbreaks at Vinh Phuc, Hanoi and Hai Duong, while another variant with the U.K. origins called B.1.1.7, which already appeared in Vietnam in previous waves, have been found among cases at Ha Nam, Hung Yen and Ha Tinh. The U.K. variant is believed to be more transmissible from ordinary strains, but doesnt take it more deadly, experts said.

Le Quoc Hung, head of the Tropical Diseases Department of HCMC’s Cho Ray Hospital, said the presence of multiple outbreaks and variants at the same time means these outbreaks are independent from each other and were stemmed from different sources.

"The virus is ever-changing. The recently observed variants would increase infection risks and incubation periods so they could infect from one person to another in a shorter time frame," he said.

While isolations and lockdowns might be very effective against local outbreaks, multiple variants and infection sources mean the virus has been spread at a much wider scale, requiring much more efforts to contain them, he added.

Patient Zero missing

In previous Covid-19 waves, the first patients to be infected with the virus have all been relatively quickly to be identified, which was especially helpful for contact tracing and quarantining. But things changed with the Hai Duong outbreak earlier this year, where by the time the virus was detected it has spread too far and wide, making it remarkably difficult to track down the original source of infection, said Hung.

The same thing is happening for the current coronavirus wave, he added.

"We totally lost track of F0 cases," said Hung, referring to patients who were infected first and placed at the first chain of transmission. The fact that most patients were largely asymptomatic also means they did not know they had the virus and still continued to travel, silently allowing the virus to fester within the community.

"They are like time bombs," Hung noted.

The inability to track down Patient Zeros means contact tracing would be much harder. Combining with the fact that authorities have been detecting a high influx of illegal entrants trying to enter Vietnam, meaning there could be those that slipped through the border undetected, the chance of the coronavirus silently infiltrating society is high, he added.

Delayed detection

The 28-year-old man who sparked the coronavirus outbreak in Ha Nam had already finished his 14-day quarantine after returning from Japan and tested negative three times, but the virus only revealed itself after that. The same thing happened with the group of Chinese experts in the Vinh Phuc outbreak and many more cases.

Tran Dac Phu, a senior advisor for the Public Health Emergency Operations Center (PHEOC), said there must have been breaches in the quarantine procedures at hotels for the virus to get out.

Truong Huu Khanh, head of the Neuro-infectious Disease Department of HCMC’s Children’s Hospital 1, said coronavirus-positive results following 14-day quarantine periods may indicate either problems with the quarantine procedures or with testing procedures.

"In general, the problem lies with human carelessness, not the disease," said Khanh.

The Ministry of Health has recently extended the Covid-19 quarantine period from 14 days to 21 days following recent incidents.

Lax mentality

People used to be much more fearful and careful against Covid-19, said Hung, evidently when streets would clear themselves and fewer crowds would be present in past outbreaks. But for this wave, citizens still decide to go out and party despite constant reports about new Covid-19 cases popping up everywhere.

Authorities have busted numerous occasions of people still going to karaoke parlors despite existing bans to such places for Covid-19 prevention. Some people even neglected self-isolation protocols and endangered public health in the process.

Past coronavirus control successes and high trust in the government may have made people become more relaxed against the threat of the coronavirus, Hung said.

"It is especially alarming as the people play a vital role in the Covid-19 fight," he said. "If outbreaks are not quickly extinguished, Covid-19 would spread in a large scale," he warned.