Saturday, August 15

Part 2, Dealing with H1N1 swine flu outbreaks in U.S. schools: CDC advice about non-medical strategies and what's wrong with it

This entry picks up from the Wednesday one, which addressed the CDC's updated guidelines to U.S. schools for the deployment of non-medical or 'non-pharmacological' interventions (NPIs) to mitigate the effects of swine flu outbreak in a school while keeping the school open.

My analysis is based on information in the CDC's online handbook, Technical Report for State and Local Public Health Officials and School Administrators on CDC Guidance for School (K-12) Responses to Influenza during the 2009-2010 School Year, a version of which will be published on August 23 for colleges and offices.

Unfortunately the handbook's headers and subheaders are not hyperlinked, which means a hunt if you want to check out the specific topics I reference, but in general the guidelines are divided into two broad categories:

"Recommended responses under conditions with similar severity as in spring 2009"

"Recommended additional responses during times of increased influenza severity"

The handbook doesn't elaborate on what is meant by "severity" in either case, which leaves open whether the CDC is referring to the size of flu outbreaks in schools or the lethality of a virus.

But from various discussions in the handbook I'd guess "severity" in this context refers to the size of outbreaks; this, on the supposition that if a more lethal strain of flu appears in the USA during the upcoming school year, the CDC would advise that schools close, whether or not students had been vaccinated.

The CDC's advice to schools about the use of NPIs is clearly based on their opinion that most swine flu infections are mild. In the earlier post I addressed two of the handbook's NPI recommendations:

1) "infection symptom screening of students and staff when they arrive at school," which pertains to a more severe outbreak.

2) schools should set up a 'quarantine' or isolation room for sick staff and students until they can be transported off the premises.

The second recommendation applies to both types of severity.

To review: I found the advice about a screening process to be inadequate -- so inadequate that it was clearly intended only to identify, in the most haphazard fashion, an ill student or staff person in the school. In other words, the advice steered clear of the use of screening measures for the purpose of limiting the spread of a swine flu outbreak in the school.

That makes sense because if the CDC ever recommended the kind of screening measures that are actually intended to slow the rate of an airborne viral infection in a school or anywhere else, their entire argument against the use of such screening measures at a country's ports of entry would collapse.

That must not happen. At all costs the sun must continue to circle the earth; to admit to the opposite would destroy the ancien regime defended by the CDC, WHO, and every other guardian of public health that considers China's approach to fighting swine flu to be apostasy.

With those sarcasms off my chest, the recommendation about an isolation room was so poorly thought out that if not backed by additional strategies, it could pose mortal danger to students who were seriously ill at school with swine flu. An isolation room should only apply in combination with rapid medical intervention, which is not possible in schools without a physician on duty.

Of course ill students should be immediately separated from others in the school. But when school administrators plan for a swine flu outbreak the emphasis should be on transporting the student to a medical facility, in the event a parent or guardian is unable to get the child to a doctor within an hour of notification by the school.

Now we move to the CDC's advice on how long a recuperating student should remain out of school. During the Spring swine flu outbreak the CDC recommended at least seven days after fever had subsided. This recommendation has been chopped down to "at least" 24 hours:
Stay home when sick

CDC recommends that individuals with influenza-like illness remain at home until at least 24 hours after they are free of fever (100° F [37.8° C] or greater), or signs of a fever, without the use of fever-reducing medications.

This recommendation is based on epidemiologic data about the overall risk of severe illness and death and attempts to balance the risks of severe illness from influenza and the potential benefits of decreasing transmission through the exclusion of ill persons with the goal of minimizing social disruption.


Many people with influenza illness will continue shedding influenza virus 24 hours after their fevers go away, but at lower levels than during their fever. Shedding of influenza virus, as detected in laboratory tests, can be detected for 10 days or more in some cases. Therefore, when people who have had influenza-like illness return to school they should continue to practice good respiratory etiquette and hand hygiene when they return to school and avoid close contact with people they know to be at increased risk of influenza-related complications.

The CDC returns to seven days for outbreaks of greater severity than the Spring one:
Extended exclusion period

If influenza severity increases, individuals with influenza-like illness should remain at home for at least 7 days, even if symptoms resolve sooner. Individuals who are still sick 7 days after they become ill should continue to stay home until at least 24 hours after symptoms have resolved.

This recommendation is based on viral shedding information. Influenza virus shedding general [sic] occurs for 5 to 7 days for seasonal influenza infection. This period may be longer for persons with 2009 H1N1 flu and among young children and people who are immunocompromised.

If you observe that the second discussion of virus shedding doesn't quite comport with the first one -- it does seem they've switched horses mid-stream, doesn't it?

The first discussion of virus shedding pertains only to "influenza-like" illness. The second discussion specifically mentions the "2009 H1N1" [swine flu] virus. But now re-read the title of the manual. The guidelines pertain to "influenza" not specifically to the 2009 swine flu outbreak.

Those readers who closely followed news reports on the CDC's "new" guidelines for schools, which emphasized the "new" 24-guideline, might be slapping their forehead by this time. Yeah, the CDC palmed an ace from the bottom of the deck.

Remember, the objective is to keep the schools open this autumn and minimize "social disruption" even during a major swine flu outbreak.

For all I know the CDC has been cranking out the same influenza manual for decades, and only made a few changes to accommodate the 2009 swine flu outbreak. In any event, for schools trying to prepare for swine flu outbreaks, the second discussion about viral shedding overturns the first one, even though it's qualified ("may be longer") because only the second one specifically mentions swine flu.

That means parents and school administrators would be wise to stick with the seven-day guideline and forget the 24-hour one, unless the sick child is tested and found to have a garden-variety flu.

What's more the CDC's argument about viral shedding is irrational, if we're to assume that by "severity" of an influenza outbreak the CDC means its size rather than increased lethality, or any other significant mutation of the virus that might possibly affect viral shedding.

Of course the larger the outbreak, the more chance for larger numbers of seriously ill people and more deaths. But whether 10 people or 1,000 contract a particular virus has no bearing on how long they shed the virus.

All right. That's all my delicate nerves can stand of the CDC's logic for one day. Next I'll tackle the guidelines on hand washing and cleaning of school surfaces.

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