We face difficult decisions if we are to suppress again the spread of SARS-CoV-2, and different voices should be heard. However, such contributions should be grounded in the facts, and public health expertise and experience. This article is neither. 1/12 irishtimes.com/opinion/jack-l…
A public health specialist would give you a much better critique than I could of the errors and misconceptions in the argument; I’ll confine myself to highlighting some factual inaccuracies. 2/12
The article states that “it is reasonable to make an educated assumption that tens of thousands of cases were circulating undiagnosed throughout the country” in March and April, implying that 500-1000 cases now is less of a problem than it seems. 3/12
This “educated assumption” does not stand up to any scrutiny. We know that people with SARS-CoV-2 infection remain infectious for 7-14 days, so a good estimate of active infections is the 14-day cumulative incidence. 4/12
Our 14-day cumulative incidence of detected cases in April peaked at 170 per 100,000 population, so for a population of close to 5 million, this is about 8,500 diagnosed active infections. 5/12
The SCOPI seroprevalence study shows that for each detected case, we missed two mild or asymptomatic cases, so at peak in April, there were about 17,000 undiagnosed active infections. This is not the kind of number suggested by the phrase “tens of thousands”. 6/12
How does this compare with today? Our 14-day cumulative incidence is now 207 per 100,000, so if we are detecting, say, 70-80% of infections, we have 12,000-14,000 active infections now compared with about 25,000 at peak. 7/12
This is about half the peak, not the order of magnitude difference suggested by the article. The article also states “we only had the capacity to test 500 per day at the National Virus Reference Laboratory” compared with 80,000 per week now. 8/12
Leaving aside the rhetorical device of comparing the number per day then with the number per week now, we were in fact doing on average 5000 tests per day in April, 3000 through NVRL and 2000 in hospitals. We’re doing 14,000 per day now. 9/12
So we are doing three times as many tests now as in April, not 20 times more as the article states, and the level of active infections now is probably half what is was at peak, not, as the article implies, less than one tenth. 10/12
We have 228 people in hospital (868 at peak) and 30 people in ICU (157 at peak). We are halfway to April in cases, one quarter of the way there in hospitalisations, and one fifth in critical care. This is not the time to downplay the significance of these indicators. 11/12
If the basic facts are so badly incorrect, how valid and useful is the opinion? 12/12

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More from @President_MU

8 Oct
The exponential growth in SARS-CoV-2 infection in Ireland should make each and every one of us stop, think, and resolve again to do our part to suppress the virus, now and quickly. 1/7 Image
The call to action is the same as it has been for weeks, but much more urgent now: radically limit our discretionary social contacts, maintain physical distance and safe practices when we do meet, self-isolate and call for help with any symptoms of COVID-19. 2/7 Image
We have seen rising cases, now we are seeing rapid increases in the number of people admitted to hospital and ICU. 3/7 Image
Read 7 tweets
2 Oct
We should not ignore or dismiss the rising numbers of SARS-CoV-2 infections. We monitor hospitalisations, intensive care admissions, and with great sadness, deaths, and we know where these numbers will go if we do not suppress transmission of the virus. 1/9 Image
Case numbers have been growing exponentially, at approximately 4% per day, since late June. The daily average case count on 23 June was 9 cases. If you add 3.9% every day, you get 12 cases on 1 July, 40 cases on 1 August, 131 on 1 Sept, and 430 today. 2/9 Image
Hospitalisations are delayed, but now also growing at about 4% per day. The daily average number of people in hospital with confirmed SARS-CoV-2 infection on 3 August was 12; increase that number by 4% per day and you get 37 on 1 Sept, and 121 on 1 Oct. 3/9 Image
Read 9 tweets
2 Oct
We don’t have SARS-CoV-2 under control in Ireland. We need, as much as we ever did, to work together, with one voice and one intention, to suppress the virus. Let’s remember the fundamental protection: keep your distance. 1/6
We need and crave social contact, but the virus exploits the moments we come close as an opportunity to transmit. It’s spreading rapidly right now, between households, especially in young adults. 2/6
The message: mix with one other household, keep your distance when socializing (even in your own home), get outdoors, limit your social contacts to those that are really important to you, stay home and seek a test if you feel unwell. 3/6
Read 7 tweets
26 Sep
A useful article. The conclusions are broadly correct, but the calculations are right only if we were randomly screening large asymptomatic populations. We mostly test people with symptoms and close contacts of known cases, so the proportion of false positives is much lower 1/10
If you have symptoms, or are a close contact, the prior probability of having SARS-CoV-2 infection is much higher than the population prevalence. A close contact has about a 1 in 10 chance of being infected. 2/10
Specificity and sensitivity of a test are harder to measure than you might think. The specificity (probability of test being negative where there is no virus) used in the article is probably generous. If the specificity is 99.7%, 3 in every 1000 tests is a false positive. 3/10
Read 10 tweets
26 Sep
How are we doing? The number of new cases per day remains high. It’s possible that incidence is rising more slowly in recent days, but it’s too early to tell. If we are starting to suppress the virus again, take this as encouragement to maintain and redouble our efforts. 1/7
It’s important to look at Dublin separately. This is daily incidence per 100,000 population for Dublin, Kildare-Laois-Offaly, and the remaining 22 counties. If every county had an incidence of 5 per 100,000, it would translate into about 250 cases a day across the country 2/7
Incidence remains high in Dublin, and is rising in the rest of the country. If we look at 14-day cumulative incidence for individual counties of interest, we can see high incidence in Dublin, and the recent rapid increase in Donegal 3/7
Read 8 tweets
20 Sep
We must protect the vulnerable in our communities from SARS-CoV-2. It is our responsibility more than theirs, because the primary means to protect them is for the rest of us to suppress transmission of the virus and keep circulating virus at very low levels. 1/8
If we look back to March through to June, the number of cases in any given county in people aged 65 and older correlates with the number of sporadic cases in the community. High levels of virus in the community increase the risk for older and other vulnerable people. 2/8
This is a lethal virus, and mortality rises quickly with age. The case-fatality rate for those cases reported March to June was 0.2% in those aged 20-39, but 33% in those 85 and above. 3/8
Read 8 tweets

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