COVID-19 Third Wave Explained in 5 Charts

In just the last two weeks, the global daily tally for new COVID-19 cases has jumped more than 30%, according to TIME’s coronavirus tracker, which compiles data from Johns Hopkins University. The steep upward trend is driven by viral waves in Europe and the United States that started in August and mid-September, respectively. On Oct. 23, the daily case count in the U.S. reached a new record high, suggesting that this wave will be worse than the one that swept the country over the summer.

But despite this rapid uptick in cases, the daily death count in the U.S. is not yet rising at the same rate, and remains at lower levels than in April. At face value, a lower case-to-fatality rate suggests that fewer people who test positive for the virus are dying from it. But the virus hasn’t necessarily become less lethal; it isn’t mutating quickly enough for that to be the case.

What’s happening now is not a result of how the virus treats humans, but rather how humans are treating the virus—that is, how we test for it, how we avoid it and how we combat it. The following five charts explain how human-driven factors are, at least for the moment, keeping deaths from spiking as high as they did early in the pandemic, even as cases rise dramatically.

1. The big picture

The below chart shows the number of new daily COVID-19 cases and deaths on a per-capita basis. Compared with the U.S., the E.U. had the virus under better control in the early summer, but cases began to tick back up late in the season. The death count stayed low for some time, but surged in recent weeks, and is now on par with the U.S for the first time since April. The U.S. could follow the same path; deaths are a lagging indicator. But so far, U.S. deaths have stayed relatively flat at about 750 deaths a day, even though cases have been rising. Of course, that situation could change as winter approaches, especially if Americans become more complacent and “pandemic fatigue” sets in.

It’s also vital to also keep in mind that a coronavirus infection doesn’t have a binary outcome—that is, people don’t either fully recover or die. Many of those who survive their initial bout with the disease go on to experience mysterious and sometimes disabling symptoms for months.


2. More testing

Widespread testing is not the entire reason for U.S. cases going up (testing has been steadily increasing over the course of the pandemic, while cases have gone up and down, as shown above). But if more people are getting infected, a robust testing system can help uncover that trend—and that’s a good thing. Having better data helps researchers estimate the prevalence of the virus in a community, while rapid testing also allows people to protect others by isolating after they’ve been in contact with someone who tested positive. Widespread testing will identify the most severe cases as well as the most benign ones, including asymptomatic cases, which may account for up to 40% of all infections.

Early in the pandemic, many countries, including the U.S., were short on testing supplies. As a result, many mild cases went undetected. One U.S. study estimated that there were likely 10 times more infections between late March and early May than reported. Because only the sickest patients were being tallied as confirmed cases, the case-fatality rate was high, and the virus appeared more deadly. This is why the case-to-fatality rate isn’t a perfect indicator of how likely a person is to die from the illness: the ratio will vary depending on the number of people in a given population getting tested.

Because the U.S. is now doing more testing, this metric is more useful today than it was earlier in the pandemic, at least to assess general trends. And what we’re seeing now is a declining case-fatality rate, stemming from rising case counts and flat death death counts.

3. Public-health measures

In early March, the U.S. Centers for Disease Control and Prevention began encouraging communities with reported COVID-19 cases to enforce social distancing to limit face-to-face contact. A month later, the agency began recommending that people wear masks when near others outside of their household. These preventative measures had immediate effect in places where the virus had already taken off. For example, at Boston’s Brigham and Women’s Hospital, new COVID-19 infections dropped by half among staff after a mandatory mask policy went into effect at the hospital in late March.

Such measures have paid off for the broader population, too. While masks and social distancing can’t always prevent 100% of exposure to COVID-19, they can reduce the amount of viral particles a person is exposed to. They will then carry a smaller “viral load” in their systems, making them less likely to become severely ill. Researchers at Wayne State University School of Medicine who tracked the viral loads in nasal swab samples collected from hospitalized patients in Detroit discovered that patients who were initially swabbed in early April had a higher viral loads than those who were initially swabbed in late April and May. Lower viral load was associated with a decreased death rate. “Social distancing measures and widespread use of face masks may have contributed to a decrease in the exposure to the virus,” the authors wrote.

3. More young people are testing positive

The coronavirus poses a greater mortality risk to the elderly compared to younger people. Among all Americans who have tested positive for COVID-19, the CDC’s current best estimate is that 5.4% died and were 70 or older, 0.5% died and were between 50 and 69, and only 0.02% died and were 20-49 years old.

In the first weeks of the pandemic, the virus tore through assisted-living facilities and nursing homes, where lots of vulnerable elderly people lived. As a result, the death count skyrocketed. But over time, as the virus spread in places like bars and college campuses, the share of U.S. COVID-19 cases have skewed younger, meaning many of those becoming infected are less vulnerable to severe illness. The CDC reported last month that children and adults under 30 made up around 16% of COVID-19 cases in February through April, but by August, that group accounted for more than one in three cases.

The number of younger people contracting the virus continues to grow, contributing to the rise in overall cases. Yet because they are less vulnerable to the virus, they are not driving up the number of deaths in tandem. (While young people are less vulnerable to COVID-19 in general, they can and do die from the disease, and can spread it to other people.)

5. Better treatments

Pharmaceutical companies have been racing to discover and produce drugs to treat COVID-19 patients since the onset of the pandemic. On Oct. 22, for example, the U.S. Food and Drug Administration officially approved the first drug for treating COVID-19, remdesivir, which was previously being used on an emergency-only basis. The agency has allowed other treatments via emergency-use authorizations, including dexamethasone, convalescent plasma, anti-inflammatory drugs and steroid treatments. In addition, doctors now better understand how the virus behaves in the body, and have learned how to more effectively treat patients—they’re using ventilators more sparingly and positioning patients on their stomachs to facilitate breathing, for instance.

Thanks to these treatments, hospitalized patients often have shorter and less-intensive stays. A new study from New York University researchers found that COVID-19 patients admitted to NYU Langone hospital in early March had a 23% percent chance of dying; that dropped to 8% chance by mid-June. A research paper from the Houston Methodist hospital system found that in the spring, patients stayed a median of 7.1 days, but only 4.8 days during the summer surge. The below chart shows how the hospital system altered the frequency of certain treatments from the spring to the summer. The use of remdesivir increased, for instance, while the use of hydroxychloroquine decreased.

In the U.S., about 750 people succumb to the virus’s assault every day. Worldwide, it’s more than 5,000 every day. There’s hope that another human intervention—a vaccine—will dramatically drive down both cases and deaths when and if one becomes available, likely next spring. Still, considering that a vaccine will not eradicate the virus completely, and a large percentage of Americans say they’re reluctant to get the vaccine at all, public-health practices like social distancing and wearing masks will be crucial to keep the virus from spreading both before a vaccine becomes available and perhaps for months beyond.

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