A nationwide surge in COVID-19 cases and hospitalizations is raising once again questions about the trajectory of the coronavirus pandemic. In the last week, America has seen, on average, more than 56,000 cases a day, the highest since July, and there have been more than 8.1 million US cases — the most of any nation — since the start of the pandemic. As an epidemiologist, I’m frequently asked: “Are we in the second wave?” This is the wrong question. America’s preoccupation with characterizing this pandemic in waves signifies we have yet to understand what it will take to end it.
“Wave” is not a term epidemiologists typically use to describe an unfolding event. It’s less of a scientific term and more of a metaphor used to describe visible peaks in the number of cases or number of deaths. When epidemiologists do use the word “wave,” they typically don’t do so as data are rolling in. We won’t know until this pandemic is over whether or how many waves occurred.
The public’s fascination with pandemic waves probably stems from the famous observation that three peaks in deaths occurred during the 1918 influenza pandemic — an event to which COVID-19 is sometimes compared. It appears that there was a sharp increase in flu-related deaths in the spring of 1918 that abated over the summer but was followed by a much larger and more deadly surge in the fall of 1918. In the late winter of 1918, a third peak in the number of deaths occurred — larger than the first but smaller than the second.
Why there were three distinct waves during the 1918 influenza pandemic is a matter of scientific debate, but it appears clear the coronavirus is not following a similar pattern. The surge in COVID-19 cases in early spring somewhat decreased in April and May, but was closely followed by sharp increases in June. Increasing restrictions in hard-hit states probably helped reduce infections again in August. But September brought another surge, with nearly all states now seeing increases.
The numbers have never really returned to baseline. Aside from a few dips, we have continued to see a high level of transmission since COVID arrived in the winter. Though the shutdowns in spring slowed the growth in cases, for most weeks thereafter the number of cases each day has exceeded 30,000. The highest number of cases recorded in the United States on a single day (77,362) occurred in mid-July, long after states began to reopen.
People may think that a second wave might somehow signify that we are well on our way toward reaching the end of this pandemic. Unfortunately, science tells us otherwise.
Serologic studies conducted in the United States make clear that only a minority of people have probably been exposed to the coronavirus. Late last month, Centers for Disease Control and Prevention director Robert Redfield testified that more than 90 percent of the US population remain susceptible to the virus. This finding, along with ongoing questions about whether prior infection with COVID-19 protects someone from being reinfected, is a good indication that we probably have a long way to go, epidemiologically, before the threat of COVID-19 is behind us.
Even if the data could be easily described in waves, it’s a problematic comparison to use to communicate about an ongoing pandemic. Waves are natural phenomena and can’t be stopped from occurring. As others have noted, a better analogy would be wildfires. At times they can burn out of control, consuming everything in their paths, while at other times a well-coordinated response in particular areas can contain them. But wildfires continue to pop up where protections aren’t as stringent. And those fires can then spread. As the ongoing California wildfires that have consumed more than 4.1 million acres demonstrate, coordinated prevention using known methods is a better option than trying to contain a rolling disaster.
We now know what it takes to stop the transmission of the coronavirus too. Other countries have used testing, case isolation, contact tracing, and infection-prevention practices, like physical distance and masks, to bring and keep case numbers under control. Taiwan has used these measures so adeptly that they’ve managed to avoid broad shutdowns. But the United States has so far been unwilling to implement targeted public health measures. Incidence is driven by inaction.
After lifting stay-at-home orders, Arizona saw a 151 percent increase in cases over a two-week period. Governor Doug Ducey responded by implementing a mask mandate, closing bars, and expanding restrictions on other businesses. These measures are credited with achieving a 75 percent reduction in cases by August. By the start of October, every county in the state met the state’s criteria for reopening. Over the last two weeks, cases have begun to increase once again. When asked about the increases, Ducey said, “[T]he expectation should be that case[s] are going to rise” and offered assurances that such increases would not necessarily lead to expanded restrictions. When restrictions have been proved successful, especially when the stakes are life or death, it doesn’t make sense to ignore them.
The US response to COVID-19 continues along on the wrong path. In the nine months since the first case was reported in the United States, more than 220,000 have died. If we stay on this course, the worst could still be to come
To end this pandemic, we need to stop asking about waves. We need to accept that there is nothing inevitable about it. The rise and fall in COVID-19 cases is largely under our direct control.
Dr. Jennifer Nuzzo is an epidemiologist and the senior scholar at the Johns Hopkins Center for Health Security, and a senior fellow for global health at the Council on Foreign Relations. Her column appears regularly in the Globe.