Just as Beijing stood on the threshold of victory over Covid-19, a 52-year-old man with fever and chills was discovered and tested positive for nCoV.

In June, about 200 Beijingers tested positive for nCoV.

A market in Beijing, on June 22, had to close some stalls to avoid virus infection.

`The infection may have started a month ago. Asymptomatic patients, or mild symptoms, have spread a lot of virus into the environment,` said Mr. Gao Fu, director of the Centers for Disease Control and Prevention.

The outbreak in the Chinese capital also shows the challenges of eliminating potential chains of infection in the absence of a safe, effective vaccine.

The virus is still there

After temporarily controlling the pathogen, some countries have initially resumed basic activities.

New Zealand even had to mobilize military commanders to supervise testing of citizens returning from abroad to prevent a new outbreak.

Other regions, from South Korea to Germany, are battling new clusters, trying to extinguish the sparks before they become raging fires.

`We cannot assume the epidemic has ended anywhere,` said Peter Collignon, clinical professor, Australian National University of Medicine, Canberra.

According to Mr. Collignon, the low number of infections shows that the epidemic is somewhat weakened, but the virus continues to spread in the community.

Professor Raina MacIntyre, biosecurity department at the University of New South Wales, Sydney, said that Beijing health officials were only facing the `tip of the iceberg` after discovering the 52-year-old patient earlier this month.

Tan Phat Dia wholesale market was closed on June 19.

`It’s possible that the outbreak itself started weeks ago,` she said.

Immediately after the man’s case, a series of other nCoV infections were recorded, most of which were small traders and people who had shopped at the Tan Phat Dia wholesale market.

Genetic sequence analysis results show that the nCoV strain in Beijing is similar to the pathogen that has spread in Europe, creating a stream of opinions confirming that the disease was brought back to this area through imported salmon.

But CDC epidemiologist Wu Zunyou said that food processing utensils could be contaminated by respiratory droplets from traders or shoppers.

`In packaging facilities, if a worker gets sick, they will spread the virus into the environment. But this does not necessarily lead to a cluster,` said Benjamin Cowling, head of epidemiology and biostatistics

Risk from small outbreak clusters

Before discovering the infection cluster at Tan Phat Dia market, Beijing city last recorded a new case in mid-April. The patient was a student repatriated from the US, who developed symptoms after 14 days of quarantine.

After the outbreak was discovered on June 11, dozens of additional cases were recorded in the following weeks.

Beijing quickly stepped up testing, screening, treatment and quarantine of people infected with the virus, while also tracing their contacts, with the aim of stamping out growing clusters.

CDC epidemiologist Wu Zunyou said the situation in Beijing is under control.

`’Under control’ does not mean that no new positive cases will be detected tomorrow or the day after tomorrow. The epidemiological curve will maintain for a while, with the number of infections gradually decreasing,` he said.

Different handling

The number of new Covid-19 cases in Beijing is flat, but the epidemic shows no signs of being eradicated.

Beijing residents were tested for Covid-19, June 23.

Instead, health officials issued orders restricting movement in hot spots – a temporary solution to prevent the virus from spreading further and avoid disrupting the capital’s economic activities.

`China’s strategy to bring the number of nCoV infection cases back to zero is quite clear. However, the measures are sometimes too strong, which can create economic consequences, affecting health in the long run.

Meanwhile, the rest of the world is watching China, seeing whether new methods can beat the outbreak without causing further economic damage.