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Why even a small increase in Covid-19 cases is so scary

What can start small can quickly get very big.

A model of the Covid-19 coronavirus.
A model of the Covid-19 coronavirus.
Saul Loeb/Getty Images

Over the past few days, Covid-19 cases have taken an upward turn — a trend that led Centers for Disease Control and Prevention Director Rochelle Walensky to say she has a sense of “impending doom.”

The increase might seem small; the US is still better off than it was in January. And news about America’s Covid-19 vaccine rollout keeps getting better and better. But there’s a reason Walensky and other public health officials and experts are still so worried about the uptick in cases: exponential spread.

With Covid-19, as well as other infectious pathogens, the start of new waves of disease comes slowly. But as more people get infected with the virus, the surge starts to pick up. Pretty soon, daily new cases can start doubling in a matter of days or weeks — and by then, any reaction from the public or policymakers is doomed to be too little, too late. It’s made even worse by the possibility of coronavirus variants: As the virus spreads and replicates exponentially, it gets more chances to mutate, potentially leading to another new, possibly more infectious variant.

So now is the time to redouble efforts against the coronavirus — before things get out of control. That means continuing the basic precautions that have long worked against Covid-19: social distancing, masking, and testing and tracing. It also means speeding up America’s vaccine rollout.

The good news: This could be the last threat of a Covid-19 surge that the US has to deal with, at least in the near future. With the vaccine rollout picking up nationally, America is now on track to vaccinate every adult by July 4. Once that happens, the threat of the coronavirus could very well be behind us — barring any new variants or needed refreshers in immunity if the vaccines’ effects prove to be temporary.

But with the end so close, experts say now is not the time to ease up. Every single infection, hospitalization, and death that’s avoided now is an infection, hospitalization, and death that truly might never happen. The finish line is near, and the goal should be ensuring more people make it across.

“Summer will be great,” Brown University School of Public Health dean Ashish Jha wrote. “How many get infected now, sick or die next month is up to us.”

Covid-19 cases have picked up across the US

According to the CDC’s tracker, Covid-19 cases have ticked up a bit over the past couple of weeks. On March 14, the country reported a recent low below 53,000 cases a day, on a weekly average. Most recently, as of March 29, the country neared 62,000 cases a day.

A chart showing daily new Covid-19 cases per capita. Our World in Data

That has not yet translated to a significant increase in hospitalizations or deaths nationally. But hospitalizations and deaths tend to be a lagging indicator — people can take days or even weeks to land in the hospital once they’re infected, and then deaths can occur a few weeks after that.

The increase seems to be driven by surges in a few states, including Michigan, New York, New Jersey, and Connecticut. Notably, Covid-19 hospitalizations and deaths in Michigan — which has seen one of the worst recent surges — have already trended up.

The national increase in cases is likely tied to a variety of factors: the public easing up on precautions, policymakers relaxing restrictions, and more infectious coronavirus variants reaching the US.

Now that increase is causing concern among health officials that America could be seeing the sparks of a fourth surge. Covid-19, like other epidemics, tends to start slowly, with the spread of the virus rapidly picking up as more people get infected.

For example: During the US’s third surge, in the fall, the country took about one month to double from around 40,000 to 80,000 cases. But then it took only around two weeks for cases to double once again, from 80,000 to 160,000 cases. That’s exponential spread.

The goal of public health is to avoid letting the situation get this bad to begin with. In fact, with Covid-19 cases still so high — the US’s recent plateau of around 50,000 cases is still higher than its plateau before the fall surge — the preference would be to bring cases lower, as close to zero as possible. That’s why Walensky is sounding the alarm now.

Instead, states are moving in the opposite direction. Over the past few weeks, state leaders have eased their Covid-19 restrictions — with some, like Texas, ending their mask mandates entirely. There’s good evidence that the restrictions, including mask mandates, work, so the states’ moves could help cause the fourth surge the CDC’s director is now worried about.

It’s particularly alarming, though, because these states may only have to hold out a little while longer to avoid any more surges.

The end of the pandemic is near. Let’s make sure more people make it.

America’s Covid-19 vaccine campaign is truly getting better. The country has gone from administering fewer than 1 million shots a day before President Joe Biden’s inauguration to nearly 2.8 million a day as of March 30. At the current rates, every adult in the US could be fully vaccinated by July 4 — a new kind of Independence Day.

We’re probably already feeling some of the effects of these vaccine efforts. According to the CDC, about 73 percent of adults 65 and older, the group that represents roughly 80 percent of Covid-19 deaths, have gotten at least one shot, and nearly 50 percent are fully vaccinated. It’s likely that the high vaccination rate for older Americans is already saving a lot of lives — and may prevent a potential fourth surge from being as deadly as past waves.

But that’s not to say the end is here; it’s merely near. More than half of the very vulnerable 65-plus population still isn’t fully vaccinated, and around 80 percent of the rest of the adult population still isn’t fully vaccinated. There are also big racial disparities, with white people more likely to have received their vaccine so far than their Black or Hispanic peers, even as Covid-19 has hit Black and Hispanic communities harder. That leaves hundreds of millions of people in vulnerable populations still susceptible to the virus.

The known coronavirus variants, and the possibility that more might emerge, are also a reason for concern. Some known variants are more infectious and can partly overcome immunity — not enough to nullify vaccine-induced immunity, based on the evidence so far, but still a concerning sign. There’s a lot of anxiety within public health circles that the coronavirus could find the right set of mutations to completely overcome the current vaccines, putting us all back to square one in fighting the pandemic.

The one way to prevent the development of new variants is by slowing the spread of the coronavirus. Every time the coronavirus infects another host, it quickly replicates so it can continue spreading. With each of these replications, there’s a chance that the virus will mutate. If that mutation proves beneficial to the virus and catches on more broadly, that could develop into yet another variant of concern. The best way to prevent all of this is by ensuring the coronavirus doesn’t find new hosts to replicate in and spread through to begin with.

This has to be done globally — a variant that shows up in another country could easily end up in the US, as we’ve seen with the variants first found in the UK, South Africa, and Brazil already. But Americans can begin this work at home.

For the public, stopping a fourth wave and discouraging the growth of new variants means taking the usual precautions against the virus, like social distancing and masking, and getting a vaccine when it’s available. For lawmakers and the health care system, it means holding steady on restrictions for now and speeding up the vaccination campaign.

The US can finally see the end of the pandemic. But between now and then, possibly tens or hundreds of thousands of people could die to Covid-19, depending on how bad we let things get. Making sure a fourth surge never comes is the one way we can guarantee that more of our family, friends, and neighbors make it to that finish line. The history of Covid-19 shows that to really do that, though, the country will have to take action sooner rather than later.

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