Fears persist of a second wave of COVID-19 in North America. What are the warning signs and how should countries prepare? Asia may provide some lessons.

Terms such as second wave, spikes, or clusters of cases are becoming widely used as the world contemplates potential further outbreaks of the coronavirus. Medically speaking, a second wave refers to the resurgence of infection in a different part of a population after an initial decrease.

According to the WHO, past pandemics, such as the so-called Spanish Flu of the early 20th century, have been characterized by “waves of activity spread over months.” Isolated clusters and regional spikes in infection numbers have already occurred in Asia, providing clues as to what to expect—and how to deal with them. The Hokkaido region of Japan was one of the first in the country to impose severe lockdown restrictions in late February. By mid-March, the number of new cases had fallen to one or two a day. By April, schools had reopened.

Less than a month later, however, the state of emergency was reintroduced as the island began to struggle with an abrupt second wave of infections. That second restriction has now been lifted, but officials admit they may well have to lock down again in the future—at least until a vaccine is found.

China, South Korea, Hong Kong, and Singapore have seen similar second wave outbreaks and introduced a range of innovative measures to tackle the crisis. Hong Kong, for example, has established systems, such as electronic bracelets for those arriving from overseas, to track people’s movements and ensure quarantines are adhered to. Elsewhere, as early as February, South Korea had developed a system to conduct about 10,000 free tests daily, while relying on apps and GPS technology to track cases and quash fresh outbreaks of the virus.

A cluster of new infections in mid-May, following weeks of almost no new cases, was quickly traced to specific locations and a total of 90,000 people in Seoul’s popular nightclub district. Three hundred infections were eventually linked to the area. In Singapore, two unrelated clusters were linked by carrying out serological tests on two individuals who turned out to be asymptomatic. It was a crucial breakthrough that helped authorities contain the virus at that point.

In Singapore, immunity testing is also being done among vulnerable sectors of the labor force, for example among pre-school teachers, to determine who can go back to work. According to experts, health systems that are sufficiently well funded are also likely to be better prepared for a second wave of outbreaks with key issues such as the mental health of healthcare workers under far more scrutiny than during the first wave. Yet nothing is guaranteed. “There is no single measure or tactic that has made the difference on its own,” Dr Naoko Ishikawa, WHO’s Covid-19 Incident Manager for the Western Pacific Region, said recently in an interview with the BBC.

“It’s not testing alone or physical distancing restrictions alone. Many of the countries and areas in this region have done all of these things, through a comprehensive whole-of-government, whole-of-society approach.”