Why is the 2nd wave leveling off?

Just from checking various dashboards (NY Times, state health departments, CDC, etc) it looks like the 2nd wave of COVID case counts is now flattening across many states. As expected, we have a rising trend of fatalities from the 2nd case wave.

My question is, what’s causing case levels to drop off? I see no change that explains it. There’s no vaccine, there’s no new public policy to stop spread, there’s no change evident in the general public’s behavior. I understand Trump is canceling funding for clinics in Texas, Illinois, New Jersey, Pennsylvania and Colorado, but I don’t think that goes into effect until August (today is Jul 30). I know Trump has asked that the CDC be cut out of the data reporting loop, but that’s not the sole avenue for reporting cases (state health departments also report cases).

So what gives with the recent flattening?

I thought we were still in the first wave.

That’s correct. We are still in the “first wave.” Different states have had their first waves at different times. New York and California had the first first waves. Places like Texas and Florida started their first waves later, and are still in the midst of it.

We are in wave 1 surge 2, I think.

Texas put a mask ordinance in about a month ago. The current leveling may be related to that.

Agree. Texas mandated masks and shut down bars and large venues at the beginning of July. The governor allowed the large cities to mandate masks (after a lot of begging) toward the end of June. Many cities and counties in Florida started mandating masks and closing bars. California mandated masks and rolled back other reopening things but I can’t remember what offhand.

Could be several things, or more likely a combination of all of them:

  1. Lots of places DO in fact have new policies in place, like the mask ordinance MandaJo mentioned.

  2. Coronavirus has been in the news 24/7 for the last few weeks, with the result that many people ARE changing their behavior. I know social media (and sometimes mainstream news) tend to obscure this by supplying endless viral photos of people in coronavirus hotspots playing full-contact beer pong, but that’s because recreational outrage drives clicks, not because this is actually representative of how people are currently behaving in general.

  3. Right now, a lot of people rarely have close contact with others outside of their household. Realistically, these people have a very, very low chance of contracting the virus, and an even lower chance of spreading it if they do get it. Meanwhile, people who DO have lots of contact with others are increasingly likely to have had it already if they live in a place where it’s widespread, so sooner or later communities start to run low on new people who are likely to be infected, even if they’re nowhere near the official herd-immunity threshold.

I wouldn’t rule this out as a factor. The Trump announcement was on 7/15, which is pretty much exactly when this flattens out.

Optimistically, 45 million+ people in the US have already been infected and are no longer in the pool of possible infections. Given there have been approximately 4.5 million confirmed cases and the CDC estimates this undercounts true infections by a factor of 10, this would mean ~14% of the US has at least some amount of immunity going forward.


The first wave in Illinois is resurgent, and growing. I can’t understand why people think the sacrifices of the past 4 months should be thrown away. Deaths are down, levelling off and holding steady. Not dropping. But new cases in Illinois are on the up. When this first wave has been controlled, and people have gotten the chance to catch their breath, then talk to me about a second wave.

Yes, the change in reporting rules exactly corresponds to a fairly dramatic change in the slope of daily cases. I know there are other reporting channels and I haven’t done any kind of correlation analysis, but Florida and Texas turned right around after the 15th.

There were some early studies suggesting that a significant proportion of the population may have cell-mediated immunity deriving from prior exposure to other coronaviruses. Even without this, there may be high variance in susceptibility to infection. And that implies a natural slowdown (decrease in R0) when a significant number have been infected (see @Trom above), since the more susceptible people are infected early. It’s even possible that we may be approaching herd immunity in places like New York.

There area a lot of unknowns here, and the U.S. will be the place where these questions are answered. We’re the world’s pioneer experiment on letting the disease get completely out of control and discovering the dynamics of the path to herd immunity. It’s hard to imagine any endpoint other than herd immunity now in the U.S., with or without a vaccine.

My working theory is that virus spread is effectively slowed when enough of the public does the bare minimum practice to limit public contact and avoid strange respiratory droplets.

ISTM that the virus should have buzz-sawed right through Tokyo, being a dense international city with heavy public transit use, but they barely had any outbreak of note. I can’t think of any reason Tokyo should be special, but I know the Japanese public has always been diligent about masking just for routine seasonal illness.

By contrast I can’t see why the virus ever would have stopped in Texas or Florida or other conservative-ideologue states. They’re nowhere near the 60-80% needed for herd immunity. All I can figure is things suddenly started getting bad and a handful of people got scared and started distancing and masking, and the curve has flattened as a result.

It’s not all business as usual in Texas. Remember, the state is conservative, but the cities are liberal, so mask compliance is not a political issue. The state has limited the power of cities to deal with this, but dense municipalities still have some power. Plus, it’s getting to the point that we all know someone who has died or been very sick. In Dallas, traffic is still very light, masks are the norm, and it’s clear that people are heavily modifying their lives in response to COVID.

Are there are any discernible differences between Tarrant and Collin counties and Dallas? Because it’s fairly hard to find such stark political, and to some extent demographic, differences in other directly neighboring places, I would think. Isn’t Collin County one of the reddest counties of its size in the entire nation?

I honestly don’t know, in terms of on the ground compliance. I don’t go north, often, especially now, so I don’t see much. Their county judge has been highly resistant to closures.

@MandaJo’s comments apply equally to Florida. We’ve gotten real serious in the D-leaning major metro areas. We still suffer from lots of yong people who think outdoors in a group is safe, but that’s not nearly as crazy as it was when our Trumpist governor opened everything.

RIght now you’d never know FL was a state full of retirees. You simply don’t see gray haired people out anywhere hardly at all. We’re all hiding indoors using delivery. Meanwhile the young-ish people are loving it; lots more room at the beach & restaurants and no ugly wrinkles spoiling the scenery.

That plus rampant fakery in the White House’s official “statistics” is more than enough to explain what’s you’re seeing.

I can attest to this in San Antonio. People largely wore masks and definitely wore masks when the mayor and county judge started challenging the governor. Unfortunately, with the reopening, people went to bars and restaurants like everything was fine and we ended up with a terrible outbreak. We slowly started to crawl back after the city mandated masks and even before bars were shut down. It’s going to be a long hard slog back to where we were at the beginning of May.

So why didn’t ALL or at least most of the states flatten out at that point. Illinois and Misery have been on a steady trend up the whole month.

Looks to me like once a state hits about 2% (20k/1m) infected the curve flattens and drops. The states that hit it last spring have stayed relatively low. States that had an initial surge but got nowhere near 2% are currently climbing again. Somewhere on this board is a link to a study stating 40-60% of the population tested have T-cells that respond to and may mitigate or minimize Covid infections. This could put natural herd immunity starting at close to 50% already. 2% times the undercounted X10 factor may be all that is needed to get Covid down to the seasonal flu numbers going forward. This could possibly explain why one person gets it and their spouse that has been with them throughout does not. Also this could explain why the elderly are much harder hit.

There’s a an autocorrect error there, I think you meant Ill-inois and Misery.

States that got hit first tended to be more densely populated. More densely populated states tend to vote Democratic. Democrats tended to lock down harder and ease up restrictions slower. Correlation is not causation. For a counter example, look at Louisiana. They got hit hard first along with the northeast, and they’re getting hit hard now, just like the Republican led states.