Things are pretty grim at the moment. Ireland's 7d rolling average of confirmed #covid cases, per 100k of population, leads the world after we were at the other end of a similar ranking only a few short weeks ago. 1/

But confirmed cases always underestimate true infections. The degree of the underestimation increases as testing is stretched. This means there are probably lots of undiagnosed infections in the community at the moment, thereby increasing our exposure risk more than ever. 2/

We can build models to predict true infections from cases, test positivity rates, and deaths. Several models exist, using different approaches and making different predictions. By combining them we should be able to produce a more accurate estimate of true infections. 3/

Below shows the actual num of cases & estimated true infections (using an avg of 4 models). The shaded area represents the num of undiagnosed infections. Currently, ~60% of true infections may be undiagnosed. That's down from 80% a few weeks ago & it's been ~90% in the past! 4/

In fact, since March >80% of infections in Ireland have probably been missed. While that might sound alarming, we must remember there are lots of asymptomatic & mild cases (still contagious though) & 80% is in line with other countries; see for eg. 5/ https://www.theguardian.com/world/ng-interactive/2021/jan/10/one-in-five-have-had-coronavirus-in-england-new-modelling-says.

Ireland's Oct confirmed cases peak was associated with fewer peak infections (~3k) than the infections (~7.5k) for April's peak cases. Today's peak in cases is associated with more infections (~17k) than either but we've yet to peak! In other words: it's worse now than ever. 6/

Prevalence, as 14d sum of cases/infections per 100k, is a rough estimate of active cases/infections. Diff between infection & case prev = active undiagnosed infections/100k. Can use this to estimate the probability a contact will be infected (but undiagnosed) = exposure risk. 7/

Exposure risk may be useful as a rough guide to just how risky external contacts are, all other things being equal. There's a higher risk now than at any other time; approx 1 in 50 (0.02) people may be infected (undiagnosed) & odds will continue to reduce until after we peak. 8/

Of course, all other things are not equal. Not only is exposure risk higher than ever, but the risk of transmission is too because the new UK variant has begun to take hold in Ireland. Coming into contact with this variant increases the risk of transmission significantly. \\9

So, more than at any other time in this pandemic, the best thing to do, the right thing to do, –– for ourselves, our families, friends, colleagues & community –– is to stay home & away from as many others, as much as we can. If we do, things will start to improve so much sooner.