# 4468
Self isolation – at least to the extent practical – when one has the flu is the best way to contain and reduce the spread of the virus.
Simply put . . . if you are sick . . . stay home.
As @Caroldn on Twitter advised last October (see Take The Pledge):
If you get sick, pledge to yourself: "This germ stops with me" Don't pass it forward.
But of course, it isn’t quite that simple. Knowing when you are no longer contagious isn’t easy.
The CDC first recommended that people infected with pandemic flu stay home for a week, but later relaxed that recommendation to 24 hours without a fever (without the use of fever reducers).
CDC Recommendations for the Amount of Time Persons with Influenza-Like Illness Should be Away from Others
October 23, 2009
CDC recommends that people with influenza-like illness remain at home until at least 24 hours after they are free of fever (100° F [37.8°C]), or signs of a fever without the use of fever-reducing medications.
This is a change from the previous recommendation that ill persons stay home for 7 days after illness onset or until 24 hours after the resolution of symptoms, whichever was longer.
This, the CDC admits, won’t stop all contagious individuals from going to work or attending school, but they believe interdicts the majority of those who are shedding significant levels of the virus.
Last August I wrote of this dilemma in They Walk Among Us, when these new recommendations were first announced.
This has immediately raised concerns that flu victims who may still be shedding virus, are being told it is okay to return to work or school.
Critics also point out that we’ve seen reports that some percentage of H1N1 patients never develop a fever to begin with.
Fever, critics maintain, is an imperfect gauge of infection.
And they are right, of course.
Using fever as a criteria will, no doubt, allow some infected people to walk among us; at work, at school, at the mall . . . and these people will probably be shedding some quantity of virus, and may go on to infect others.
Of course, we also know that those infected with the flu virus can begin shedding virus 24 hours before they show symptoms, and that some percentage of infected remain asymptomatic for the full course of the infection.
They walk among us, too.
Coming up with guidelines that balance public health concerns, and practical considerations, isn’t easy. Particularly when – no matter what recommendations are made – many people will opt not to follow them.
Since last fall, we’ve seen several studies that suggest that even the initial recommendation of staying home for a week would not corral every infectious individual.
These studies detected viral shedding in individuals beyond the currently accepted self-isolation period.
DSA: Kids Shed Virus Longer Than Adults
Swine Flu: The Gift That Keeps On Giving
It should be noted that shedding enough virus to be detectable by today’s modern RT-PCR testing or virus culture, and being contagious and able to spread the virus, may be two entirely different propositions.
Today, we’ve another study that appears in the CDC’s Journal of Emerging Infectious Diseases that calls into question the infectious period of the H1N1 pandemic flu.
Here is the abstract (reparagraphed for readability). Follow the link to read it in its entirety.
Contagious Period for Pandemic (H1N1) 2009
De Serres G, Rouleau I, Hamelin M-E, Quach C, Skowronski
D, Flamand L, et al. Contagious period for pandemic (H1N1) 2009. Emerg Infect Dis. 2010 May; [Epub ahead of print]We estimated the proportion of persons with pandemic (H1N1) 2009 who were shedding infectious virus at diagnosis and on day 8 of illness. In households with confirmed cases, nasopharyngeal swabs were collected on all members and tested by PCR and virus culture.
Of 47 cases confirmed by PCR at <7 days of illness, virus culture was positive in 92% (11/12) of febrile and 63% (22/35) of afebrile persons.
Of 43 persons with PCR-confirmed pandemic (H1N1) 2009 from whom a second specimen was collected on day 8, 74% remained PCR positive and 19% were culture positive.
If the 73 symptomatic household members without PCR-confirmed illness are assumed to have pandemic (H1N1) 2009, a minimum of 8% (6/73) of case-patients shed replicating virus on day 8.
Self-isolation only until fever abates appears insufficient to limit transmission.
Self-isolation for a week may be more effective, although some case-patients still would shed infectious virus.
Obviously fever is an imperfect criteria for determining if someone should stay home with the flu. If coughs and respiratory symptoms abated along with the virus, that might make a good litmus test, but they don’t.
Often people carry a cough for days or even weeks after the flu has passed.
While the `fever rule’ is easy to criticize, it isn’t easy to come up with a better criteria that people can easily and will willingly follow.
And any criteria you could come up with would fail to intercept those with asymptomatic or sub-clinical infections from spreading the virus.
Which shows just how insidious a foe influenza is to combat.
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