2009 Flu Season is Upon Us

Updated: August 27, 2009

Background:

The emergence of novel Influenza A (H1N1) virus (a.k.a “swine flu”) has caused that even now during the summer, we continue to see flu. In fact, outbreaks have occurred in summer camps and with initiation of school year. As of August 21, 2009, in the US 7,893 persons with novel H1N1 have been hospitalized, and 522 deaths have been reported.

The “swine flu” appears to be more transmissible than seasonal flu, likely because there is little prior immunity in the population, but so far it does not seem to be more severe. Nobody can predict the future but there is a good possibility that this coming flu season (fall and winter) we will see co-circulation of novel Influenza A (H1N1) and seasonal A (H1N1). This means, the season may be busier than usual and the treatment decisions may be more complicated.

Testing:

Testing for “swine flu” is a 2-step process at this moment. You can do a rapid test in your office or your reference lab can do a “confirmatory” test (such as DFA) but that will identify the virus as “flu A” only. Keep in mind that the test is less than perfect and will identify only ~50% of cases (in other words will miss ~50% of cases). And if the result is flu A-positive, the specimen then has to go to the lab at the Louisiana Office of Public Health (OPH) to be especially processed to differentiate “seasonal” flu A (of which there are 2 types: H1N1 and H3N2) or novel H1N1 (which is the “swine flu”). Only at that moment you can say it is “swine flu”. In practicality, though, because there is no seasonal flu circulating yet, every case of flu A we are seeing now has been confirmed to be novel H1N1. Because of the large number of cases, the OPH is only processing specimens from patients who are severe enough to be hospitalized and the test will take a few days to be processed.

Because there is no difference in what your recommendations to the patient may be (whether seasonal or “swine flu”), at least for mild cases, you need not bother to test everyone. If flu symptoms (fever, body aches, runny or stuffy nose, sore throat, nausea, vomiting, diarrhea) are present, assume it is the “swine flu” and treat as such (see below).

And, keep in mind there is no point in “screening for swine flu” (ie, testing children who have no symptoms but may have been exposed): the test will not be positive; if the test is positive, likely it is a false-positive; and it will never go for confirmation, anyway. 

Treatment:

Similarly, not everyone needs to be treated with antivirals. Children who have mild symptoms need to remain at home, avoid contact with others, keep good hydration and use antipyretics (Tylenol or Motrin but no aspirin). The vast majority of cases will recover well. Use of antivirals should be reserved for those who have severe symptoms or have underlying conditions that put them at risk for severe influenza. In those cases antivirals should be started promptly. Similarly, prophylaxis to contacts is not routinely recommended but in those households where one of the members qualify as a risk group.

And choosing what antiviral to use is not that easy either. The novel H1N1 is sensitive to Oseltamivir (Tamiflu) but the seasonal flu is not. Both are sensitive to Zanamivir (Relenza), but, all this may change as the season progresses. As of today, since what is circulating is the novel H1N1 (“swine flu”) and since it is still sensitive to Tamiflu or Relenza, either one is currently recommended for treatment or prophylaxis. But again, this may change soon, so we will keep you informed.

Vaccination:

Meanwhile, similar to previous years, the best intervention will be vaccination. Be aware that the seasonal flu vaccine does not protect against “swine flu”, so two separate vaccines will be required. While there will be a novel H1N1 vaccine it will be separate from the seasonal flu vaccine. In other words, people will have to receive two different vaccines.

The seasonal flu vaccine is now available. It is advised that as many people as possible get this vaccine to decrease as much of seasonal flu as possible. That includes pediatric population, pregnant women, health care workers and anyone with significant underlying medical problems.

And then, likely in mid-October, will come the novel flu A (H1N1) “swine flu” vaccine. Chances are this vaccine will require two doses. For this vaccine, since the supply may be limited, CDC has established priority groups that should receive it first.

The groups recommended to receive the novel H1N1 influenza vaccine include:

• Pregnant women
• Household contacts and caregivers for children younger than 6 months of age
• Healthcare and emergency medical services personnel
• Anyone older than 6 months of age with chronic medical conditions
• All people, prioritized by age group: 1) 6 months through 4 years of age, 2) children 5 through 18 years of age, 3)  young adults 19 through 24 years of age, and 4) persons aged 25 through 64 years of age

Prevention:

Sources of Information:

We will keep this site updated as new information becomes available, so visit us frequently. You can also e-mail Dr Rodolfo E Bégué (rbegue@lsuhsc.edu) with any question (we will post your question and the answer) or call Dr Bégué at (504) 896-9820. You can also find all sorts of information at CDC’s website (www.flu.gov). Dr. Begue is Professor of Pediatrics, Division Head, Infectious Diseases at LSUHSC & Director, Infection Control, Children’s Hospital, New Orleans.