A stunning graph this, courtesy of US company Kinsa:

The blue line in that graph represents people with a temperature in New York City. The red line is deaths in New York City. If you take the temperatures, and shift them 18 days to the right, they line up perfectly with the deaths. In other words, the temperatures predicted the deaths (and cases).

Kinsa, which doesn’t operate in Ireland, makes thermometers. Smart thermometers, to be precise. Basically, the thermometer records your temperature and sends it back to Kinsa, and they send you back some helpful advice about whether your temperature is normal, abnormal, or downright dangerous.

But obviously, being a private company, they also record the data, which is helpful, even when there’s no pandemic. For example, parents can use it to find out if there’s a spike in temperatures at their children’s schools, and hospitals use it during flu season to predict admissions, and so on.

But in terms of Coronavirus, it’s worth noting that the data here tracks perfectly: Deaths (and, it’s not in the graph, but hospital admissions too) track with temperatures 18 days earlier.

In our story about Jacinda Arden the other day, and her comments about Ireland, we noted that countries that have been particularly successful at containing the virus also tend to be the countries who are conducting routine temperature screening and monitoring of people as a backup to coronavirus testing.

There are several reasons this makes sense: Obviously, while not everybody who has the virus is symptomatic, those who are will always have a temperature, especially in the early stages of the illness when they may not even know themselves that they are sick. Second, checking a temperature takes less than 30 seconds, whereas, as we know in Ireland, testing for the virus can take up to a fortnight.

Third, and this is important, it allows you to set restrictions on people according to a very fair, and transparent standard: If you have a fever, you’re not going anywhere, like it or not, regardless of whether you think that fever is a result of Coronavirus or something else. It’s perfectly fair, and obvious to people.

Finally, it lets you keep your country relatively open as normal while still imposing social distancing on high-risk individuals. Temperature checks are also non-invasive, and cheap.

It’s not impossible to imagine a situation where workplaces can open back up by checking the temperature of every employee every morning, or where families can be told to regularly check the temperatures of family members before leaving the house.

Sure, like everything else, it has some risks (is the mother of the bride really going to not go to her daughter’s wedding because she has a temperature that morning, for example) and humans will always find a way to cock up any system, or justify their own non-compliance with it, but then that’s true of lockdown as well, except that the daily costs of lockdown are much higher.

Ultimately, the single biggest problem with lifting the lockdown is the fear of a second wave of Coronavirus, and the risk for the state is that when we open up, and things go back to normal, we have a wave of infections in the population that takes about two or three weeks to show up. In other words, that the damage is done before we can see that it has been done.

Checking temperatures solves that, because, as the graph above shows, if you see a spike in temperatures, you can be fairly sure that you’re going to see a spike in the virus. And if you can screen people out purely on the basis of their temperature to begin with, you might well avoid that spike in the virus without having to go back into second lockdown.

Would it be invasive? Yes, almost certainly. For example, busy schools checking the temperature of every student and staff member every day is going to take time, and effort, and be disruptive. But is it better than having schools closed, basically indefinitely? Of course it is.

This is something other countries have been doing for some time. If we’re looking for a sustainable path out of lockdown, this must be part of the conversation.