What proportion of people with Covid19 symptoms are being tested? Reflections #34

Insight

While new Covid19 cases in Australia are staying at the low levels from the end of April, and the proportion of positive tests is reducing, we are still likely only testing under half of the symptomatic people in the community.

I’ve posted before about flutracking. It’s a weekly email survey of a self selected sample of Australians and New Zealanders normally used to track the winter flu. It asks around 70,000 people a few basic questions once a week about their health in the last week. They’ve added a few extra questions, and started it early, to enable early warning (even without testing) of whether Covid19 symptoms are starting to emerge in the community.

There are two really interesting things coming out of their weekly reports (and I’ve looked at Australia here).

First, lockdowns have massively reduced the levels of sickness in the community, from 1.5% reporting fever and cough on 23 February, to 0.2% reporting fever and cough last week. During a normal winter flu season the average of that statistic is around 2.5% over the whole season.

And second, even now that we have testing available for anyone who wants to be tested, we still only have under 50% of those people who report fever and cough being tested for Covid19. That’s better than the 1% who were being tested in the week of 23 February, but it isn’t enough to catch even all the symptomatic people. The flutracking population is self selected, and includes a disproportionate number of healthcare workers. So it is likely that the proportion of symptomatic people being tested in the flutracking population is higher than the population as a whole, as they are probably more conscientious about healthcare, and supporting community health by making sure they are tested.

As Victoria has overtaken NSW on both numbers of daily tests and numbers of reported daily cases, I’ve been wondering whether the greater number of cases in Victoria is because they are testing more. Last week, Victoria tested an average of 12,500 people a day, with a positive rate of 0.07% (around 8.5 positive cases per day). NSW last week tested an average of 7,500 people a day, with a positive rate of 0.04% (around 3 positive cases per day).  Are Victorians more conscientiously going and getting themselves tested with the slightest symptom? Or is there genuinely more Covid19 in the community in Victoria?

Given estimates of asymptomatic carriers are around 50% (here’s the Diamond Princess study, for example), it would be reduce the risk of more outbreaks if we were at least testing all the symptomatic people. Maybe we need popup testing centres at shopping centres, now that people are out shopping again?

Link

Fitbit has released some analysis of how people using fitbits are in better health (as measured by their heart rate), on average, during lockdown than they were at comparable times in January.

What we discovered is encouraging: across the US, when comparing the baseline data from January to that of February, March, and April, we saw that resting heart rate improved—which means that it declined—for the general population, skewing more so for younger users. We also looked at international data, which saw similar trends.

There were three main reasons for the improvement they found from the data:

• more intense exercise (despite lower step counts)
• longer sleep duration
• more regular bedtimes

Sleep duration increased. As shared in our data story about global sleep patterns, we know that sleep duration has increased during shelter-in-place. In fact, 45 percent of people have increased their sleep time, while 30 percent have maintained their average sleep duration. This is great news, especially because not getting enough sleep can have a negative impact on resting heart rate. Not getting enough sleep is a risk factor for cardiovascular disease.

I found it fascinating that two of the three reasons were about sleep health – after reading a book about sleep (Why we sleep), I’m a convert to the importance of sleep. I know that now I’m not commuting, I haven’t been setting an alarm, but waking up naturally. While I don’t track my sleep, I suspect I am getting more and feeling better for it.

Life Glimpses

My running group has started meeting again for weekly runs (maximum 10 people, with full social distancing). I’ve been a bit of a dilettante for the first week and stayed in bed (since they like getting up early!), but it has been lovely to see how much fun everyone has had seeing each other again despite the restrictions on what they can do. I’ve been so impressed with how much fun the group has had during lockdown with facebook exercising and virtual communal running around a theme, that I feel I know the group so much better than I ever could have by just meeting up for a 10K run on a Saturday morning.

I’m still not sure if I can bring myself to get up for it at 6.30 on a Saturday morning, though. I might stick to my solo running and evening online sessions for a little while.

Bit of beauty

As we start to move towards winter (which in Sydney means more rain) we are still getting lovely breaks of sunshine. Which, for geekinsydney‘s flower pictures, means some beautiful effects of the rain on the flowers.