Via The Conversation, Dr. Melissa Hawkins of American University writes: The US isn't in a second wave of coronavirus – the first wave never ended. Excerpt:
After sustained declines in the number of COVID-19 cases over recent months, restrictions are starting to ease across the United States. Numbers of new cases are falling or stable at low numbers in some states, but they are surging in many others. Overall, the U.S. is experiencing a sharp increase in the number of new cases a day, and by late June, had surpassed the peak rate of spread in early April.
When seeing these increasing case numbers, it is reasonable to wonder if this is the dreaded second wave of the coronavirus – a resurgence of rising infections after a reduction in cases.
The U.S. as a whole is not in a second wave because the first wave never really stopped. The virus is simply spreading into new populations or resurging in places that let down their guard too soon.
To have a second wave, the first wave needs to end
A wave of an infection describes a large rise and fall in the number of cases. There isn’t a precise epidemiological definition of when a wave begins or ends.
But with talk of a second wave in the news, as an epidemiologist and public health researcher, I think there are two necessary factors that must be met before we can colloquially declare a second wave.
First, the virus would have to be controlled and transmission brought down to a very low level. That would be the end of the first wave. Then, the virus would need to reappear and result in a large increase in cases and hospitalizations.
Many countries in Europe and Asia have successfully ended the first wave. New Zealand and Iceland have also made it through their first waves and are now essentially coronavirus-free, with very low levels of community transmission and only a handful of active cases currently.
In the U.S., cases spiked in March and April and then trended downward due to social distancing guidance and implementation. However, the U.S. never reduced spread to low numbers that were sustained over time. Through May and early June, numbers plateaued at approximately 25,000 new cases daily.
We have left that plateau. Since mid-June, cases have been surging upwards. Additionally, the percentage of COVID-19 tests that are returning positive is climbing steeply, indicating that the increase in new cases is not simply a result of more testing, but the result of an increase in spread.
As of writing this, new deaths per day have not begun to climb, but some hospitals’ intensive care units have recently reached full capacity. In the beginning of the outbreak, deaths often lagged behind confirmed infections. It is likely, as Anthony Fauci, the nation’s top infectious-disease specialist said on June 22, that deaths will soon follow the surge in new cases.
