Tuesday, Dec 24, 2013
Influenza Health Alert
In the last week, we have seen a definite increase in the presence of influenza in our community. A number of rapid influenza lab tests have been positive, and several visitors have been seen in the clinics, bringing with them a history of laboratory confirmed influenza, and now with spread of clinically compatible illness to family members, effectively exposing all of us!
In California, influenza is also on the rise, with levels above baseline, and expected for this time of year. Remember, the peak is classically in mid-February, so this is just beginning. We have no idea at this point how severe the flu season will be.
However, an interesting pattern is beginning to develop, as illustrated in the following report from the Texas Department of Public Health. It is expected that this will be replicated around the country. Texas is one of 4 states with widespread disease. As expected, 90% of the disease is Type A. What was not expected is that 90% of the Type A cases are of the 2009 H1N1 strain, which is in the current vaccine. A hospital is the Houston area had 8 admissions, and 4 died. None were elderly. You may recall that the 2009 H1N1 strain is particularly significant in attacking a younger population, particularly age 25-65. In 2009, the death rate among children tripled!
Statewide influenza-like illness (ILI) activity continues to increase and is above baseline levels. ILI intensity is high in Texas, and influenza is now widespread. All Texas regions have reported laboratory confirmed influenza. Over 90 per cent of positive influenza tests reported from Texas laboratories have been typed as influenza A. Of those influenza A viruses that have been subtyped, 90 per cent have been the 2009 pandemic H1N1 subtype. This subtype of influenza is included in this season's [2013-14] influenza vaccine. No novel influenza cases have been reported in Texas. No antiviral resistant influenza strains have been reported in Texas.
Influenza viruses can be spread by large respiratory droplets generated when an infected person coughs or sneezes in close proximity to an uninfected person. Symptoms can include fever, dry cough, sore throat, headache, body aches, fatigue, and nasal congestion. Among children, otitis media, nausea, vomiting, and diarrhea are common. Most people generally recover from illness in 1-2 weeks, but some people develop complications and may die from influenza. The highest rates of influenza infection occur among children; however, the risks for serious health problems, hospitalizations, and deaths from influenza are higher among people 65 years of age or older, very young children, and people of any age who have medical conditions that place them at increased risk for complications from influenza.
Everyone who is at least 6 months of age should get a flu vaccine this season [2013-14]. It is not too late for vaccination. There are several flu vaccine options available for the 2013-2014 flu season. All these vaccines contain the currently circulating H1N1 strain. We do not recommend one flu vaccine over another.
Rapid Lab Test
Rapid influenza diagnostic tests (RIDTs) can be useful to identify influenza virus infection, but false negative test results are common during influenza season. Clinicians should be aware that a negative RIDT result does NOT exclude a diagnosis of influenza in a patient with suspected influenza. When there is clinical suspicion of influenza and antiviral treatment is indicated, antiviral treatment should be started as soon as possible, even if the result of the RIDT is negative, without waiting for results of additional influenza testing.
Treatment: oseltamivir and zanamivir are chemically related antiviral medications known as neuraminidase inhibitors that have activity against both influenza A and B viruses. Early antiviral treatment can shorten the duration of fever and illness symptoms, may reduce the risk of complications and death, and may shorten the duration of hospitalization. Clinical benefit is greatest when antiviral treatment is administered early, especially within 48 hours of influenza illness onset. Decisions about starting antiviral treatment should not wait for laboratory confirmation of influenza.
Antiviral treatment is recommended as early as possible for any patient with confirmed or suspected influenza who
- is hospitalized,
- has severe, complicated, or progressive illness,
- is at higher risk for influenza complications.
Persons at higher risk for influenza complications recommended for antiviral treatment include:
- children aged younger than 2 years,
- adults aged 65 years and older,
- persons with chronic pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, or hematological disease (including sickle cell disease); metabolic disorders (including diabetes mellitus); or neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy [seizure disorders], stroke, intellectual disability [mental retardation], moderate to severe developmental delay, muscular dystrophy, or spinal cord injury),
- persons with immunosuppression, including that caused by medications or by HIV infection,
- women who are pregnant or postpartum (within 2 weeks after delivery),
- persons aged younger than 19 years who are receiving long-term aspirin therapy.
- American Indians/Alaska Natives.
- persons who are morbidly obese (that is, body-mass index is equal to or greater than 40).
- residents of nursing homes and other chronic-care facilities.
Clinical judgment, on the basis of the patient's disease severity and progression, age, underlying medical conditions, likelihood of influenza, and time since onset of symptoms, is important when making antiviral treatment decisions for high-risk outpatients.
Additional details regarding antiviral treatment can be found at
There is speculation that the H1N1 virus circulating in Texas may be a new [more virulent?] drifted or reassorted strain. It seems likely that the fatalities observed in Texas are due to a possibly more virulent strain of the seasonal H1N1 influenza virus, rather than a novel pathogenic agent. Further information is awaited to substantiate this conclusion.
In the meantime:
- We encourage everyone who is not vaccinated to get their annual flu vaccine. There is plenty of vaccine, available at healthcare providers, pharmacies, and the health department.
- Stay home when sick
- If you are well and healthy, don’t assume that flu is a mild illness. It can kill you!
- Cover your cough, wash your hands – you know the drill!
And, stay well. Happy holidays!
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