Fall is here, school is back in session, and once again it’s time to gear up for flu season. This year will have special challenges, as we are preparing for both seasonal flu and H1N1 (swine) flu.
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The pandemic H1N1 flu (aka “swine flu”) began in April, and circulated in daycares, schools and camps over the summer but dropped off until very recently increasing to widespread levels again in many states. Virtually all the flu around now is the pandemic H1N1 virus. The H1N1 virus also predominated in the recent winter months of the Southern Hemisphere, which typically spreads north as we have our winter. There is concern that we are now experiencing a second wave of H1N1 this fall with the return of children to school.
You may have H1N1 if you have fever (temperature > 100 degrees) AND either cough or sore throat. Fever is present in 94% of cases, cough in 92%. Other possible symptoms include chills, runny nose, headache, muscle ache, and in less folks, nausea, vomiting and diarrhea. Seventy percent of hospitalized cases have high risk conditions (including pregnancy), but 30% are apparently healthy young persons, so everyone needs to be careful to practice respiratory infection control.
Pandemic H1N1 flu affects the young with 5% occurring in persons older than age 50. It's mostly affecting children 5-14 years, but children 0-4 years are most frequently hospitalized (MMWR, 8/28/09). Those at higher risk include children with neuro-developmental disorders (e.g. cerebral palsy, developmental delay, MMWR, 9/4/09) and pregnant women who are four times more likely to be hospitalized for H1N1 infection (Lancet, 8/8/09). Those with asthma/COPD (emphesema/chronic bronchitis), diabetes, immuno-suppression (e.g. chronic steroids, chemotherapy or transplant patients), cardiac disease, pulmonary disease, renal failure, and chronic liver disease have increased risk. Obesity may be a separate risk factor. Persons > 60 may have some immunity to the H1N1 virus if they were exposed to H1N1 in 1976 or earlier outbreaks.
Since essentially all flu currently circulating is still pandemic H1N1, lab testing is not helpful at this time. If you get pneumonia after an ILI (Influenza-like-illness) or those with risk factors you may ask your doctor to test you and treat you with Tamiflu. Testing options for include the rapid influenza test (only 40-70% able to rule it out) or the H1N1 PCR test (more accurate in ruling it in). It is not useful to test if you've gotten over influenza or for screening for influenza for camp, vacation, school, or work to see if it's safe to go back. You could ask your doctor for a chest x-ray (CXR) if you have a ILI (Influenza-like-illness) with shortness of breath, abnormal vital signs other than fever, or a pulse oximetry of 95 or lower on room air. This is especially so for those with risk factors.
Patients with ILI (Influenza-like-illness) AND risk factors AND no reason to have a fever from illness outside the respiratory tract may benefit from Tamiflu. This is only useful when started within 72 hours of starting symptoms Since the vast majority of patients without risk factors recover fully, they don't typically benefit from Tamiflu. If you get pneumonia (seen on a CXR) soon after an ILI, consider asking your doctor for both antibiotics AND Tamiflu even if it's more than 72 hours after your symptoms started. This is more helpful for those who are more sick. Some very sick pregnant women with H1N1 and pneumonia have benefited from Tamiflu even starting a week after symptoms started.
Tamiflu is not recommended for prophylaxis-- to prevent getting H1N1. It is most appropriate for persons who have high risk conditions (e.g. pregnancy) and who are household contacts of suspected or confirmed H1N1 patients. There are a few reports of Tamiflu-resistant pandemic H1N1 viruses. With one exception, it has occurred in persons receiving Tamiflu for treatment or prophylaxis, a compelling case to limit unnecessary use. Studies of anti-vira drugs (Tamiflu and Relenza with limited data sets) show no evidence of toxicity to either pregnant or breast-feeding moms (CMAJ 7/7/09). Because of the potential danger of H1N1 in pregnancy, CDC strongly recommends treatment of pregnant women with an ILI.
Folks with with ILI should stay home and isolate themselves as much as possible. In addition, they should consider these measures: surgical masks for patient and caregivers, gloves for caregivers, separate room for patient, keeping high risk persons out of the house, frequent hand-washing with hand sanitizer or soap and water.
Folks with fever plus cough, sore throat, or nasal congestion suggestive of influenza-like illness (ILI) should consider using surgical mask to prevent large respiratory particles from spreading to others and surfaces other folks touch. Although N-95 masks plus gloves are recommended for health care workers, they have not been recommended for the general public. They require careful fit testing to be effective (they spray a bitter tasting mist inside a plastic cone around your head-- if you taste it there isn't an effective seal with the mask).
Frequent hand washing is helpful, and when not available, alcohol hand rubs are very effective. After many applications of the hand rub, a residue builds up that must be washed off to continue effectiveness of further applications. Contaminated surfaces and door knobs can be wiped down with a virucidal product such as CavicideTM or Caviwipes XLTM or other cleansers.
The new CDC recommendation for most persons states a person can end self-isolation at home when they are free of fever > 24 hours (when not taking anti-pyretics such as acetaminophen or ibuprofen). For health care providers and day care workers the old rule still applies: seven days after onset of illness or 24 hours after symptoms are gone, whichever is longer (resolution of symptoms means fever is gone and coughing much less). This gives a good idea of when to return to work, school, and lab testing is not necessary.
The seasonal flu vaccine is now available. This is the usual vaccine that protects against the three flu strains that have circulated in various forms over the last 30 years. The H1N1 vaccine may be available in late October. Priority groups for the first round of H1N1 vaccination will probably include persons 6 months - 24 years, household contacts of infants < 6 months, pregnant women, persons 25-64 years with chronic medical conditions, and health care workers and first responders.
More details at: http://www.cdc.gov/h1n1flu/
Feel free to ask more questions in my upcoming Web Chat at 9am PST on 10/20/09. You can register at http://www.medhelp.org/health_chats/register/34