States are beginning to reopen, prompting fears about a spike in new cases. We asked the experts: how likely is that to happen?
Danielle Renwick – The Guardian
Miami Beach in Florida on Wednesday. Is a second wave inevitable? Photograph: Chandan Khanna/AFP/Getty Images
States and cities across the US are continuing to reopen, despite states such as Texas and Arizona reporting an increase of cases since Memorial Day. These reopenings, along with ongoing protests, have raised concerns about a “second wave” of infections.
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How do you define a ‘second wave’ of infections?
Elaine Nsoesie In an epidemic curve, the number of cases go up, peak, and start going down. After that, if you have a consistent increase over a short period of time – some people have been using 14 days – that could be described as a second wave.
David Rubin I think of a second wave as a true recurrence of widespread community transmission. When [places] reopen, you’re going to get some increased transmission, but I don’t think increased transmission alone is a second wave.
It’s becoming fairly clear that there are about four epicenters in the country right now that are starting to coalesce: the south-west, the state of Texas, the state of Florida, and then the lower mid-Atlantic – South Carolina and North Carolina.
Whether it’s a first wave or a second wave following a ripple, these are kind of semantics.
Are second waves inevitable as states reopen?
Rubin No. Certainly increased transmission is, but you can avoid a second wave. Places like Colorado are doing extremely well right now [Editor’s note: Colorado’s stay-at-home order expired on 26 April]. Colorado public health folks had good messaging on how people [can adapt] their individual routines and be vigilant around moments of [potential] transmission.
At the end of the day, it comes down to community norms and routines. If everyone is just trying to go back to normal and not face the inconveniences – like mask-wearing and avoiding large gatherings – then the risk for a second wave goes up.
Nsoesie There’s a lot happening in the US. Because it’s summer, people are going out, and then you have the protests and all types of gatherings are happening. It looks like there’s a very good chance that most states are going to see a second wave.
But it’s not inevitable. New Zealand might be a good example of a place that can reopen safely without experiencing a second wave.
Is it safe to travel to a place – like Texas or Florida – that’s having an increase in cases?
Jessica Justman I would certainly think very carefully before traveling to these places. If you go, you would want to be particularly careful with staying 6ft apart from people, hand-washing and not touching your face. All of these things remain really important. You don’t want to be in a place where lots of people are not wearing masks.
Is it safer to be somewhere like New York, where the number of cases is still high but transmission is falling, or somewhere like Florida, where there are fewer cases but transmission is on the rise?
Rubin The safest thing now is wearing your mask on the subway, [avoiding] overpacked indoor locations, being discerning about which restaurants you go to, washing your hands.
That’s the safest thing, no matter where you live.
I’ll give a personal example: at the beginning of this epidemic, as we started to understand that temperature and humidity were important to mitigating transmission, we left my 86-year-old mother down in south Florida, because we knew that the first wave came through, it would be safer for her down there.
But as Florida started to reopen, and New York started degrading its case counts, we flew her back up here. I made that decision based on my knowledge that New York is much safer than other areas of the country right now.
How do we know that a rise in reported cases isn’t simply due to an increase in available tests?
Rubin Take a look at the testing positivity rate. If it’s just about increased testing capacity, your test positivity rate goes down because you’re flooding the market with tests. Because you’ve had so many tests, the number [of total cases] go up. So when you see increasing case numbers and decreasing test positivity rates, that suggests the test, and it’s just an artifact of testing capacity.
What is the likelihood that second waves in states like Texas and Florida will carry over to other states?
Justman There’s much less air travel now, so the chance of a second wave in some states carrying over to other states is lower. Is there total isolation? No, but there’s a lot less travel.
Are you concerned about second waves in cities that have seen protests over recent weeks?
Justman Yes, but the risk of a second wave with the lifting of restrictions and even with the protests may be offset by the fact that more people wear masks.
Rubin The demonstrations occurred outside, and in an area like New York City, where you had already degraded your cases pretty significantly, you might see a bump, but I don’t think it will be a second wave. I suspect that areas that have been doing well [at lowering transmission] will continue to do well.
Nsoesie States and cities can be more proactive. Instead of waiting for people to start showing up at hospitals, we could provide resources so that people who’ve been at the protests can get tested early, and if they’re infected, start contact tracing as soon as possible.
Are there still concerns that a second wave will happen in the fall?
Nsoesie We know that we have higher cases of influenza starting in the fall, and that’s one of the reasons why we would expect an increase in [coronavirus transmission] the fall. More people tend to spend time indoors compared to now, when people are out in parks and open spaces.
Justman We’re still trying to figure out how sensitive the virus is to temperature and humidity. It’s hot in Texas now but we are seeing an increase in new cases. This virus is not wilting away in very hot, humid settings.
During the Spanish flu, it started in the spring and came back with a vengeance in the fall and winter. So everybody is bracing for that.
I think a modest second wave is coming, and then contact tracing and other measures will be put in place to get on top of it. The real question is what’s going to happen in the fall. That’s why there’s a huge push to get vaccine trials running.
Elaine Nsoesie, assistant professor of global health, Boston University School of Public Health
Jessica Justman, professor and attending physician in the division of infectious diseases at the Columbia University Irving Medical Center
David Rubin, director of PolicyLab at Children’s hospital of Philadelphia and a professor of pediatrics at the Perelman School of Medicine at the University of Pennsylvania