Why does the delta variant seem to rise and decline in two-month waves? – Poynter

Why does the delta variant seem to rise and decline in two-month waves? – Poynter

October 6, 2021 Off By administrator

Covering COVID-19 is a daily Poynter briefing of story ideas about the coronavirus and other timely topics for journalists, written by senior faculty Al Tompkins. Sign up here to have it delivered to your inbox every weekday morning.

Let’s not bury the lead: Many of the important indicators about the pandemic are positive. The number of new cases, hospitalizations and even deaths are declining in most places.

But this post is about what we are learning about this virus. As everyone suspected, the delta variant acted in the United States similar to how it acted in other countries — with two and a half months of increase then a steep decline.

(Our World in Data)

That is not to say it had to happen this way. The decline may have occurred because people started rethinking personal protection and more people got vaccinated. But, let’s face it, our decline has not been as fast or steep as some other places that have more strictly enforced mandates. And the two-month decline is not true everywhere yet.

(Financial Times)

Why do we have virus waves? Epidemiologist Dr. Katelyn Jetelina explains some factors:

Human behavior: Once numbers start increasing, people start changing behavior (whether they know it or not). Even modest restrictions can bring numbers back down, like masking or cancelling plans. People did take the Delta wave seriously. The Kaiser Family Foundation reported an uptick in vaccinations due to Delta, hospitals filling up, and knowing someone who got seriously ill or died due to Delta. Human behavior plays a big role in wave patterns.

Seasonality. During non-pandemic times, most coronaviruses are seasonal. Other viruses, like the flu, are seasonal because of climate patterns (and human behavior). It’s not a coincidence that our largest COVID19 wave was during the Winter months. But, again, this doesn’t fully explain all waves, as we had some during the summer months too.

Social networks:  As people see their regular contacts and these networks reassert themselves, Delta runs out of places to go. This is highly dependent on how and where people mix. As we all know, schools just started, which would open social networks (not limit them). So, this may only play a limited role with Delta.

A note about the last point: By social networks, Jetelina is referring to the people we interact with most. When we are social distancing, we tend to interact with people who are most like ourselves, so vaccinated people tend to hang out with others who are vaccinated. The virus has fewer opportunities in that scenario. When we are less careful about social mixing, viruses have new opportunities.

We do not know if the coronavirus is a two-wave or a multi-wave virus. If you look at what happened 100 years ago, the flu arrived in three waves over two years. Wave two was the big one. The dates were March 1918, September 1918 and February 1919.

(National Institutes of Health)

Some experts theorize that the first wave spread the…

(Excerpt) To read the full article , click here
Image credit: source