WHO: Virus has become a pandemic.

The spread of the coronavirus is now a pandemic, officials at the World Health Organization said Wednesday.

“We have rung the alarm bell loud and clear,” said Tedros Adhanom Ghebreyesus, WHO’s director-general.

Tedros called for countries to learn from one another’s successes, act in unison and help protect one another against a common threat.

“Find, isolate, test and treat every case, and trace every contact,” Tedros said. “Ready your hospitals. Protect and train your health care workers.”

“Let’s all look out for each other, because we’re in this together to do the right things with calm and to protect the citizens of the world.”

Although this is the first pandemic caused by a coronavirus, “we also believe that this is the first pandemic that is able to be controlled,” Tedros added.

He pointed several times to the success of China, which has cut new infections from more than 3,500 a day in late January to a mere 24 in the most recent daily count. The world is watching to see whether China can keep its numbers down as it gradually releases millions of city dwellers from quarantine and lets them go back to work.

South Korea and Singapore have also begun to see cases drop. But the rest of the world is seeing alarmingly rapid rises.

The WHO is emphatically not suggesting that the world should give up on containment, Tedros said.

“We are suggesting a blended strategy,” he said, referring to a blend of containment and mitigation. “We should double down. We should be more aggressive.”

China, South Korea and Singapore have shown that aggressive contact tracing and rapid isolation of the sick can work. Unlike Western nations, all three rejected the idea of home quarantine, because cases rapidly spread in families.

Wuhan and surrounding cities, the outbreak’s epicenter, have been shut down since late January, and travel elsewhere is strictly limited. Everyone must wear a mask outdoors and submit to constant temperature checks, which are administered at the doors to every office building, store and restaurant, as well as bus, train and subway stations — even at the entries to apartment houses and residential neighborhoods.

The use of sanitizer or hand-washing on entry is mandatory. People who think they are infected are screened at special “fever clinics,” not at doctors’ offices. They get temperature checks, flu tests, white blood cell counts, CT lung scans and laboratory tests for the virus, according to Dr. Bruce Aylward, leader of the WHO observer mission that visited China in February.

Anyone who appears to have the new virus, instead of flu or bacterial pneumonia, is held until the lab results are in or while testing is repeated. Some are held at repurposed hotels. If they are found to be infected, they may not return home — almost 80% of infections were within families, studies in China found.

If infected persons are seriously ill or elderly, they are hospitalized. Those with milder cases recuperate in isolation centers with hundreds of beds and nursing care. The centers are segregated by sex and age; even children who are infected must go.

No visitors are allowed, but there activities like dance classes to fight the boredom and keep people active.

As difficult and aggressive as they are, such measures “reduce the number of cases that are wheeled through the doors of hospitals,” said Dr. Michael Ryan, head of the agency’s emergencies program.

The goal of an aggressive containment response, WHO officials explained, is to hold down the number of deaths and critical illnesses until a vaccine can be rolled out, possibly by early next year.