Here's a study showing that it might work (scenario 1 is doing nothing and scenarios 2 and 3 are intervening at 1% illness and 0.1% illness):
The attack rate drops the sooner you intervene with NPI's. Adding treatment and targeted anti-viral prophylaxis (TAP) adds further benefit. However, there are practical aspects of intervening too early, so there are always balances and trade-offs:
The timing of initiation of various NPIs will influence their effectiveness. Implementing these measures prior to the pandemic may result in economic and social hardship without public health benefit and may result in compliance fatigue. Conversely, implementing these interventions after extensive spread of a pandemic influenza strain may limit the public health benefits of an early, targeted, and layered mitigation strategy. Identifying the optimal time for initiation of these interventions will be challenging, as implementation likely needs to be early enough to preclude the initial steep upslope in case numbers and long enough to cover the peak of the anticipated epidemic curve while avoiding intervention fatigue.
You can see from that (and the detailed description) that this is not an exact science. And let me repeat this: implementation likely needs to be early enough to preclude the initial steep upslope in case numbers. That's the answer to "but there's only one case! Why are we doing this?" If you wait for "the steep upslope", it's too late to matter.
But is it all theoretical? Not hardly. In 1918, during the terrible pandemic of that year, Philadelphia
refused significantly delayed NPI (closing schools, canceling public gatherings), and look what happened compared to St. Louis, which did.
Isn't that a startling mirror of the "goals of community mitigation" curve? It's meant to be. Everything that we are describing is an attempt to be St. Louis and not Philadelphia, even though this year's version is so much milder.
Now, remember, the milder the virus, the less intervention and community mitigation is needed, and the less the plan calls for:
Note that in the above table, it's likely that even a mild pandemic will kill more people than an average seasonal flu. That's what makes it different than seasonal flu even when it's described as "mild". In this context, "mild" means only 3-10x the amount of deaths as usual. And it could turn out to be more.
But when you don't know, in the beginning, how things are sorting themselves out then you err on the side of caution. You can always pull back. And the degree of disease and death will dictate how long the schools close for. The more severe the pandemic, the longer the schools will stay closed.
Now, there are current and active interim recommendations from CDC as to when to close schools:
CDC recommends that affected communities with laboratory-confirmed cases of influenza A (H1N1) virus infection consider activating school dismissal and childcare closure interventions according to the guidelines below. "Affected communities" may include a U.S. State or proximate epidemiological region (e.g., a metropolitan area that spans more than one State’s boundary). These guidelines address a flexible and scalable approach that States and local jurisdictions can use based on the situation in their communities (e.g. number of cases, severity of illness, affected groups)...
Dismissal of students in a school and closure of childcare facilities should be considered in schools with one or more laboratory-confirmed or non-subtypable influenza A case among students, faculty or staff in order to decrease the spread of illness in the community.
Beyond that, the detailed guidance suggests close collaboration between school officials and public health officials.
State-wide closure would only happen in a Category 2-3 (where it can be "considered") or greater (it's "recommended for category 4-5"). and that can't happen until we determine that A) we have a pandemic and B) we know the severity and therefore assign a category. But as we discussed above, in the US we already have virus spread (if/when it spreads elsewhere, WHO will declare a pandemic), so health officials are acting now based on what we are seeing today. We don't have a declared pandemic and we don't know what category we are in (maybe a 2, maybe a good deal less). Until we know, the precautionary principle applies and the interim CDC guidelines will be followed.
There are no predictions that can be made about the fall. Whether this virus disappears, smolders, or returns, will have to be carefully monitored.
So, back to the job of public health officials. If they do their job, there'll sometimes be the appearance of over-reacting. If they don't there'll be the appearance of being asleep at the switch. Richard Besser (Acting Director, CDC) in particular, and the entire team is doing very well, but there's a lot more to explain, including that the virus could be back in the fall, that vaccine will take six months to produce (and even then, will need to be prioritized to essential workers first), and that CDC doesn't decide if your local school closes... and when it re-opens. Behind the scenes, communication has also been excellent. In a way, this is a country-wide tabletop for a worse event that still may come (maybe not for years, but eventually it will.) But don't judge things just yet. This story is still in the early chapters.
In the meantime, there's more to discuss, especially about surveillance, vaccines, health reform, and public health infrastructure. But for today, pay attention to school closings and understand why they are happening.
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