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H1N1 (Swine Flu): When is it safe to go back to work and Failure of Rapid Flu Tests

August 7, 2009

AMOUNT OF TIME PERSONS WITH INFLUENZA-LIKE ILLNESS SHOULD BE AWAY FROM OTHERS

CDC has issued new guidance to help businesses, schools and families manage isolation time of ill persons.  On August 5, 2009, CDC changed its recommendation related to the amount of time people with influenza-like illness should stay away from others (the is called the “exclusion period”).

  • New guidance indicates that people with influenza-like illness should stay home for at least 24 hours after their fever is gone (without the use of fever-reducing medicine).
  • A fever is defined as having a temperature of 100° Fahrenheit or 37.8° Celsius or greater.

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 will be helpful this fall flu season as the CDC has also recommended that employers and schools not ask for a authorization from a MD to return to work or school as this will clog up the health care system which will already be severely challenged with ill persons.

Isolate ill persons with a temperature above 37.8 C or 100 F

Isolate ill persons with a temperature above 37.8 C or 100 F

A few key points:

  • The new recommendation applies to camps, schools, businesses, mass gatherings, and other community settings where the majority of people are not at increased risk for influenza complications.
  • CDC recommends this exclusion period regardless of whether or not antiviral medications are used.
  • This guidance does not apply to health care settings where the exclusion period continues to be for 7 days from symptom onset or until 24 hours after the resolution of symptoms, whichever is longer. (See http://www.cdc.gov/h1n1flu/guidelines_infection_control.htm for guidance on infection control in health care settings.)
  • Decisions about extending the exclusion period should be made at the community level, in conjunction with local and state health officials. More stringent guidelines and longer periods of exclusion may be considered for people returning to a setting where high-risk people may be exposed.

Guidance for Sick Individuals and their Care Givers

  • Sick individuals should stay at home until the end of the exclusion period, to the extent possible, except when necessary to seek required medical care.
  • Sick individuals should avoid contact with others.
  • Keeping people with a fever at home may reduce the number of people who get infected, since elevated temperature is associated with increased shedding of influenza virus.
  • When people who have had influenza-like illness return to daily life they should continue to practice good respiratory etiquette and hand hygiene and avoid close contact with people they know to be at increased risk of influenza-related complications.
  • Because some people may shed influenza virus before they feel ill, and because some people with influenza will not have a fever, everyone needs to cover their cough and wash hands often.
  • Medications to reduce fever containing acetaminophen or ibuprofen, are appropriate for use in individuals with influenza-like illness.
  • Aspirin (acetylsalicylic acid) should not be given to children or teenagers who have influenza; this can cause a rare but serious illness called Reye’s syndrome.

This guidance will continue to be updated as more information becomes available and the pandemic evolves.



CDC http://www.cdc.gov/h1n1flu/guidance/exclusion.htm

QUICK TESTS FOR THE FLU FOUND OFTEN INACCURATE

As H1n1 spreads, many medical providers are turning to rapid tests that can determine within minutes whether a patient has the flu and  sales of these tests are soaring.  As reported in the NY Times and the CDC, the tests may fail more than half the time to detect H1N1 infections.  The low sensitivity of the tests is becoming a concern to health authorities because a false negative reading might prompt a doctor not to prescribe antiviral drugs.

A nasopharyngeal culture

A nasopharyngeal culture

Not to accurate

Whether or not to use this rapid tests in the fall will be one of the big issues laboratory directors face as they prepare for what is expected to be a rush of flu testing this flu season.  A study published recently in The Journal of Clinical Virology found that one rapid test detected only 10 percent of the H1N1 infections that could be picked up by a more sophisticated laboratory culture.  CDC released in its own study, three rapid tests detected 40 to 69 percent of the swine flu cases. The rapid tests performed better on the seasonal flu, picking up as many as 80 percent of the cases. This prompted CDC to issue new updated guidance urging doctors to be cautious in relying on the tests.

What does a rapid test test?

The rapid tests do not tell if a patient has the swine flu. They say only if flu is present, or in some cases whether it is type A or type B influenza. The swine flu is type A, but so are many seasonal flu strains.  These rapid tests are similar to pregnancy tests. They use antibodies to detect a protein from the virus and if that protein is present, a colored stripe appears on the test strip. However there are often sampling errors as even a nasal sample from a patient with the flu might not contain enough of the protein to register a positive result.

NY Times http://www.nytimes.com/2009/08/06/health/06flu.html?emc=tnt&tntemail0=y

CDC MMWR http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5830a2.htm?s_cid=mm5830a2_e

CDC New Guidance for H1N1 Rapid Testing http://www.cdc.gov/h1n1flu/guidance/rapid_testing.htm

2 Comments leave one →
  1. CrescentCityRay permalink
    August 10, 2009 07:16

    I’ve always taken vaccines, but I worry this year’s flu vaccine may do more harm than good.

    • August 11, 2009 04:59

      I can certainly appreciate your concern – there is a lot of conflicting news. Do keep in mind that vaccines are the main tool of Public Health to fight many illnesses like Influenza. The more people that are vaccinated, the less circulating virus there will be and we will all likely be healthier because of that personal effort. I plan to get a seasonal flu shot and will take an H1N1 vaccine when it becomes available but since I am not in one of the priority groups, I expect it will be quite awhile.

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