As more countries look to relax lockdown restrictions, experts are concerned a second wave of coronavirus will emerge.
A resurgence of COVID-19 next winter could hit the US health care system even harder than the original outbreak has, the director of the Centers for Disease Control and Prevention (CDC) has said.
“There’s a possibility that the assault of the virus on our nation next winter will actually be even more difficult than the one we just went through,” Redfield told The Washington Post on Tuesday. “We’re going to have the flu epidemic and the coronavirus epidemic at the same time.”
Will there be a second wave?
Researchers have compared the coronavirus crisis to the 1918 Spanish flu pandemic, which is estimated to have claimed 50 million lives.
The Spanish flu swept the world in three waves over one year – and it was the second wave that proved far more deadly than the first.
Professor James Naismith, from the University of Oxford in the UK, has said it is highly likely that the world will face further waves of the virus until a vaccine is in use.
“I think everyone now realizes just how fast this pandemic can move and what the stakes are,” he warned.
How does a second wave happen?
If the first wave of an outbreak is large enough, the majority of a population can become immune to the disease. But this type of herd immunity can only be achieved by letting the virus pass through the entire population, which means more lives lost, or through vaccination that mimics an infection without causing disease.
An effective vaccine is still months away, by the best estimates, and the global population will still be susceptible to a second wave of infection when lockdowns are lifted.
China locked down Harbin, a city of 10 million people on Monday over fears of a second wave of coronavirus cases.
Seventy people have tested positive in Harbin where more than 4,000 have been tested. The new cases link to a student returning from New York.
The second wave of corona virus in China, Harbin North China. pic.twitter.com/Y7p53J6acE— bebebear我是大熊🐻 (新号) (@bebebear2020) April 20, 2020
Without a vaccine, and with no widespread immunity to the new disease, Singapore is another country which has seen a sudden second wave.
Although Singapore was initially praised for containing COVID-19 among its general population, the disease reemerged in cramped a dormitory where thousands of foreign workers without inadequate hygiene facilities live.
With 1,426 new cases reported on Monday, Singapore’s experience has demonstrated the ability of the disease to come back strongly in places where people are in close proximity.
Fears for a second wave were also heightened in South Korea as officials said at least 179 recovered coronavirus patients have tested positive for a second time.
Patients in their 20s accounted for the highest portion of patients to retest positive for coronavirus, South Korea’s Centers for Disease Control and Prevention said on Sunday.
Is a second wave inevitable?
While globally-enforced lockdowns are effectively tempering the spread of COVID-19, the same restrictions are also devastating economies and societies.
But how can governments ease restrictions without prompting a second wave? This is the question that is currently vexing global leaders and health experts.
The threat of resurgence only declines when susceptibility of the population to the disease falls below a certain threshold or when widespread vaccination becomes available.
In general terms, the ratio of susceptible and immune individuals in a population at the end of one wave determines the potential magnitude of a subsequent wave.
Preliminary studies out of Canada and Holland indicate that as few as 3 percent of people have antibodies that can defend against the virus. In certain parts of Germany and France, however, this number seems to be around 14 percent.
The worry is that with a vaccine still months away, populations worldwide remain highly vulnerable to both resurgence and subsequent waves.
“Epidemics are like fires. When fuel is plentiful, they rage uncontrollably, and when it is scarce, they smolder slowly,” Justin Lessler, an associate professor of epidemiology at Johns Hopkins University, wrote in the Washington Post in March.
“Epidemiologists call this intensity the ‘force of infection,’ and the fuel that drives it is the population’s susceptibility to the pathogen. As repeated waves of the epidemic reduce susceptibility (whether through complete or partial immunity), they also reduce the force of infection, lowering the risk of illness even among those with no immunity,” Lessler wrote.