Q&A: Why are COVID-19 cases declining in the US?
On Wednesday, CDC Director Rochelle Walensky, MD, MPH, reported that COVID-19 cases in the United States have declined for 5 consecutive weeks, and new hospitalizations have been consistently down since early January.
Deaths also have declined slightly over the past week, Walensky said, although she cautioned that the emergence and spread of more transmissible variants of SARS-CoV-2 “could jeopardize the progress we have made in the last month if we let our guard down.”
“While cases and hospitalizations continue to move in the right direction, we remain in the midst of a very serious pandemic, and we continue to have more cases than we did, even during last summer’s peak,” Walensky said.
Healio asked several infectious disease experts about these and other issues. They agreed that there is no one reason for the decline in cases.
Healio: What do you think is driving the current downward trend in cases in the U.S.?
Amesh A. Adalja, MD, senior scholar, Johns Hopkins Center for Health Security: I think the downward trend is multifactorial and has to do with the fact that travel is back to a baseline after increases over the holiday weeks, people are being more mindful of wearing face coverings, there has been a significant proportion of people infected who have some immunity and there also may be some small contribution from vaccines.
Cornelius (Neil) J. Clancy, MD, associate professor of medicine and director of the extensively drug-resistant pathogen lab and mycology program, University of Pittsburgh: I think it is multifactorial, involving some combination of behavior (masking, distancing, restricting travel and masking, getting through the holidays, etc.), seasonality, cumulative past infections and vaccination reducing vulnerable targets and perhaps some tapering off in number of tests performed.
Carlos del Rio, MD, FIDSA, Infectious Disease News Editorial Board Member and executive associate dean, Emory University School of Medicine: The rapid decline in cases in the U.S. likely has many origins. The first one is that holidays are over. We had a huge surge as a result of having Thanksgiving, Christmas and New Year’s in rapid sequence while variants were spreading unknowingly. Now that holidays are over, people are not gathering as much, then transmission has slowed down. We are also being more careful; people are wearing masks (even double masking) because of the variants. There is also testing. Testing has gone down quite a bit, and as a result, there is less case detection. Finally, there may be starting to have an impact of vaccines, but my gut feeling is that it is too early for that.
Jeanne Marrazzo, MD, MPH, FACP, FIDSA, Infectious Disease News Editorial Board Member and director of the division of infectious diseases, University of Alabama at Birmingham School of Medicine: I think it’s complex. We have gotten far enough out from the super spreader opportunities presented by the end-of-the-year holidays, and I believe the community as a whole reacted to the peaks in December and January by escalating mask use and social distancing to a considerable extent. I would like to think that vaccination efforts in the last month are playing a role, especially in the most vulnerable people and in essential (including health care) workers, but it will take some time to figure out if that is the case. Finally, I do think that in general the level of diagnostic testing is declining as efforts shift over to ramping up vaccination. That might be contributing to a decline in case counts that isn’t necessarily an accurate reflection of true underlying disease. That said, the declines in hospitalizations are indisputable, and that is very encouraging.
Healio: Are you concerned that people will start to let up rather than continue to be diligent, and that states will continue to relax measures?
Adalja: It is important to remember that we are still in a pandemic and that people have to behave accordingly. I do think it is reasonable to relax restrictions because these measures need to be tied to hospital capacity, and as hospitalizations fall, relaxing restrictions while providing guidance for venues to operate safely in this environment should be the norm.
Clancy: Yes, this will be among the greatest challenges in the weeks and months ahead.
Del Rio: Very much so. Some states are quickly lifting restrictions, and others are going about as if “business as usual.”
Marrazzo: Yes, but I think this is inevitable. We are heading into warmer weather (soon), and as more people are vaccinated, they will have more of a sense of personal security, whether that is warranted in terms of the duration of immunity provided by the current vaccines or whether they protect against incoming, emerging new variants.
Healio: Will cases in the U.S. spike again anyway because of the variants?
Adalja: It’s unclear if we will see a major spike with the new B.1.1.7 variant in the United States. It is something that needs to be prepared for. However, if we can continue to vaccinate at accelerating speeds, we may be able to forestall its becoming a major problem.
Clancy: Of course, no one knows. My guess is that SARS-CoV-2 variants will emerge and circulate, but the disease will not spike as it did over the winter or in the early stages of the pandemic. There's a chance COVID-19 fades into the background, and SARS-CoV-2 and variants are out there in the sea of respiratory viruses that circulate, in particular over cold weather months. The disease itself may very well be attenuated, in part due to some degree immunity among a large part of society.
Del Rio: Predicting the future is dangerous, especially with this virus. Let’s hope not.
Marrazzo: I don’t think they would spike if the measures you mention above continue to be used. That is why it’s so important not to let up just yet. We just don’t know how they are going to impact things.
Healio: Former CDC Director Tom Frieden, MD, MPH, tweeted this recently: “We're all SO TIRED of COVID. But there's actually a lot of good news. Cases plummeting. Vaccines steadily rolling out, with more vaccines on the way. We just need to hang in there a few more months, and the worst will be behind us.” Do you agree with that last part?
Clancy: Yes, I think the worst will be behind us. I also don't think SARS-CoV-2 or COVID-19 will just disappear completely. As I said, I suspect more of a fading into the background
Del Rio: One hundred percent. We are in a good point at the moment. Let’s keep it up. The race between vaccines and variants will be critical.
Marrazzo: I’d like to. I’m still concerned about how new variants might emerge and spread to undermine the terrific efficacy of the initial vaccines. I’d like to be proven wrong in worrying about that.
Healio: What should be the focus of public health messaging for the next few months?
Adalja: The focus of public health messaging should be on extolling the benefits of the vaccine and shifting from an abstinence-only message toward one of harm reduction, including helping people make risk calculations.
Clancy: We're almost there. Get vaccinated, continue to take measures to limit spread, as we have been doing. Then, as spring unfolds and we get to summer, we could very well be in a place that we can loosen restrictions and resume those activities that we have put on hold.
Del Rio: One of hope, one of encouragement. People are tired; we can’t continue talking “gloom and doom.” We need to hunker down but also encourage people to get vaccinated when their turn comes up and look at a brighter “COVID-free” future.
Marrazzo: Stay the course — we got this far, we’re vaccinating everyone as quickly as possible and we will not be wearing masks forever.