Ventilation is important, but other factors are equally or more important. SARS-CoV-2 transmits in droplets, fomites (particles, objects and surfaces) and aerosols. We do not know for certain the relative importance of each, so let’s be careful about all of them. 1/8
The best available evidence, and the experience of public health doctors managing outbreaks, strongly suggest that the majority of transmissions occur with close contact, close enough for droplets, and aerosols in high concentration, to transmit the infection. 2/8
We think that transmission via contaminated surfaces is rare, but touching and soiled hands are likely to be important routes of transmission. 3/8
We are, for example, seeing a significant number of transmissions outdoors, when people get too close, most likely transmissions via droplets, spray or soiled hands; a little more distance, not touching or shouting, or better hygiene might have prevented these infections. 4/8
Our own @hpscireland and the are very clear on this, acknowledging that this is a novel virus and we cannot be certain about these things. 5/8……
@hpscireland It is bad and potentially dangerous advice to suggest that physical distance, minimising direct contact and hand hygiene are not effective infection prevention and control measures, and that ventilation is somehow more effective or more important. 6/8
@hpscireland This is important. We are depending on people to do everything they can to reduce the risk of transmission, and we need to be clear in our advice, and explain it as best we can. I’m concerned that with the emphasis on ventilation, we forget the basics. 7/8
Vaccination protects, staying home if symptomatic protects, distance protects, masks protect, good respiratory hygiene protects, hand-washing protects, ventilation protects. We need to pay attention to all, and avoid crowding and getting too close, indoors or outdoors. 8/8

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More from @President_MU

19 Jul
The data are saying one thing: be very cautious faced with the delta variant. We are seeing a very steep rise in cases, comparable to or steeper than the early part of previous waves. 1/9
This will not translate into severe disease and mortality in the same way as before, but numbers in hospital are rising: 101 this morning. The ratio of admissions to cases is 16 admissions per 1000 cases, overall we are tracking 15-25 admissions per 1000 cases. 2/9
Weekend effects typically give low case counts on Sunday and early in the week; case counts over the next few days will be an important indicator. 3/9
Read 9 tweets
1 Jul
It’s worrying to see incidence appear to increase after a long period of stability or slow decline, and especially concerning that it is increasing across almost all age groups. Daily average case count 387, up from 311 one week ago. 1/4
Incidence is increasing across all age groups from 5 to 70 years of age, notably in those age cohorts where there are significant numbers of partially vaccinated people, a reminder of the importance of that second dose, and that delta exploits the vulnerability between doses. 2/4
Growth rate is estimated at about 2% per day, reproduction number 1.0-1.2. The level of infection seems to be growing again, almost certainly driven by the increased transmissibility of the delta variant, spreading in the unvaccinated and partially vaccinated. 3/4
Read 4 tweets
30 Jun
It has been a difficult and disappointing week for many, as the rise to dominance of the delta variant has delayed plans for wider reopening; but the likely impact of delta is stark, and caution is well advised. 1/36
We use scenario models to help NPHET and Government think quantitatively about risks and likely disease trajectories and impacts. The short form: we use a number of standard models, they are already published, and the effect of vaccination is included. 2/36
The first is a standard homogeneous population SEIR model. This considers the population, as a whole, moving between different compartments: susceptible (S), exposed (E), where you have the virus but cannot yet spread), infectious (I) and recovered (R). 3/36
Read 36 tweets
14 May
Dr. Mina, you have inferred a great deal about my knowledge and motivation from one tweet; fair enough, it may not have been my finest moment in pandemic communications. Nonetheless, a few points of clarification and response. 1/15
First, there is a context. This is not about antigen testing in general, which does have and will continue to have a role in our management of the pandemic. 2/15
This is about the uncontrolled and unsupported sale of antigen tests by a supermarket chain, and their (one hopes tongue-in-cheek) response to advice from @CMOIreland not to use them, as a negative test might give false reassurance that you are free of infection. 3/15
Read 15 tweets
12 May
A lot of reasons to be optimistic. While incidence is relatively high, it is stable, due to our collective efforts to minimize transmission. If we remain careful, and keep each other safe, we can see this through the few weeks until vaccination offers us greater protection. 1/4 ImageImage
Incidence has remained stable through April, and test positivity below 3% despite intense testing. The numbers in hospital and ICU are decreasing; importantly, daily admissions remain low. 2/4 ImageImageImageImage
The recent increases in incidence in children and adolescents seem to be transient, and incidence in these age groups is now trending back towards the population average. 3/4 Image
Read 4 tweets
9 Apr
We have looked carefully at incidence of SARS-CoV-2 infection in children in recent weeks for any impact of the phased return to the classroom. The data, and thorough public health investigation, confirm that schools remain a low-risk environment. 1/16
Schools are low risk because of the mitigation and protection measures put in place by teachers, principals, families, general practitioners and public health doctors. 2/16
The data show a moderate and transient increase in cases of SARS-CoV-2 infection reported in children, not directly because of the return to in-person education, but due to increased detection, or case ascertainment, related to an increase in testing. 3/16
Read 16 tweets

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