Why the second wave of COVID is so much worse than the first

The end of outdoor weather came just as we were letting our guard down. And the vast majority of us still haven't had it.

When the first wave of the COVID-19 pandemic hit Canada, the country shut down for weeks as public health experts battled to get control of the crisis. Now, with many businesses and schools reopened, the country is facing an even more serious threat in the form of a second wave of cases, hospitalizations and deaths. At some point on Monday, Canada was set to add its 300,000th cumulative case since the first was recorded on Jan. 25.

The current growth of the pandemic is occurring at a speed nearly triple that of the first wave in the spring:

  • 0 to 50,000 cases: 94 days
  • 50,000 to 100,000: 48 days
  • 100,000 to 150,000: 103 days
  • 150,000 to 200,000: 25 days
  • 200,000 to 250,000: 18 days
  • 250,000 to 300,000: 12 days

Canada isn’t alone. Ryan Struyk, a CNN reporter on the COVID-19 beat, reports that the number of new cases in the United States “has doubled in the last 20 days, tripled in the last 40 days and quadrupled in the last 60 days.”

People had months to absorb the lessons from the first wave, so why is this second wave so much worse than the first?

Not all pandemics, after all, have second waves that are harsher than their first. Tom Jefferson, a senior associate tutor at the Centre for Evidence-Based Medicine at Oxford University, looked at the 10 most recent pandemics, starting with the devastating Russian flu pandemic that swept the world in 1989-92 and ending with the current COVID-19 crisis. Of those 10, six did not involve second waves that were more or equally severe as the first. One example is the SARS pandemic that started in 2002 and quickly died out the next year, after spawning deadly outbreaks in several parts of the world, including China and Canada. In total, the World Health Organization recorded 8,437 cases of SARS globally, with 813 deaths.

However, the most famous pandemic, 1918 Spanish Flu, which infected as many as half a billion people and killed approximately 50 million, had far deadlier second and third waves in the fall and winter of 1918-19. The reasons it did are still debated. That influenza infected both humans and swine, while the unhygienic chaos surrounding the end of the First World War also contributed (the health crisis began 12 years before Alexander Fleming discovered penicillin.)

There were early indications that the COVID-19 pandemic could have a towering second wave. “Coronaviruses tend to be more common in the winter,” says Ashleigh Tuite, an infectious disease epidemiologist and mathematical modeller at the Dalla Lana School of Public Health at the University of Toronto. So, the arrival of COVID-19 in late winter/early spring meant its emergence was out of season. That timing was fortuitous as it didn’t spread as well in unfavourable conditions, particularly warmer weather, allowing everyone time to get cases under control.

The new coronavirus prefers indoor transmissions, though Tuite notes that experts aren’t sure whether it’s a characteristic of the virus itself, or the impact of human behaviour (i.e. our inability to wear masks and keep distanced while inside). Now, with colder weather, we’re spending much less time outside and more time indoors, which is ideal for this type of virus. As well, the “the initial wave didn’t affect a lot of people; only one per cent was infected in the first wave,” Tuite says, meaning the population of Canada remains highly susceptible at a time when conditions in this country are suitable for spread.

Since the spring, epidemiologists have done everything but jump up and down on TV to warn that round two could dwarf what most nations endured in the first. “Beware COVID-19’s second wave this fall,” was the headline on the American Medical Association website on May 8. In the article, Marc Lipsitch, a professor of epidemiology at the Harvard T.H. Chan School of Public Health sounded the alarm: “We will have a harder time controlling coronavirus in the fall,” he wrote, adding: “We will all be very tired of social distancing and other tactics. The hard thing will be to keep enough of it to protect our ICUs and keep the number of cases from flaring up.”

In June, Dr. Lisa Maragakis, a specialist in infectious disease at Johns Hopkins Medicine, was concerned that human behaviour would play a major part in a second surge, saying, “People are frustrated. Cellphone data are showing decreased social distancing.” Sure enough, as governments relaxed public health rules and reopened their economies, people responded by gathering in increasingly large numbers on restaurant patios and in backyards, often without consistent masking or distancing. Surges of new cases were reported after every major holiday, including Canada Day, Labour Day and Thanksgiving.

Lipsitch foresaw the difficulty faced by governments who tried to balance the dangers of a second wave with the economic and societal costs posed by restrictions, saying in June: “Almost every government is talking about lifting control measures. Not every government, but many, because of the economic burdens. But the downside is that many jurisdictions will have a plan to open up but not a plan to re-close.”

His warning proved prophetic, as many governments delayed imposing restrictions, though cases were surging and experts were increasingly vocal about the hazards of such late action on vulnerable populations.

The psychological differences between the two waves are also key to explaining why this second is so dangerous, Tuite says. In the spring, the focus was the virus. The pandemic was new; there was a camaraderie as everyone adapted to the “new reality.” Now, it’s all about human behaviour.

“It feels different. It’s only November, days are longer and it’s harder psychologically,” she says. “We’ve missed a lot of celebrations and milestones, and Christmas is coming up.” So it’s easier to bend the rules a little bit, she believes, with many thinking: “I will follow most of the recommendations but it’s not a big deal if I have a couple of people over to my house.” With many months looming ahead before vaccines may be widely available, it’s hard to change those habits which are spreading COVID-19, and harder still to sustain those changes once they’re made.

“It’s incredibly frustrating,” says Tuite. “I’m tired. The conversations we’re having today are not that different from those we’re having in March.” While there is huge resistance to shutting things down again, we may not have a choice. “I don’t know what the alternative is,” says Tuite. “At a certain point, if you don’t have a strong public health system in place, there’s not anything else to do…with so much infection in the population, things will shut down anyway.”