Novel H1N1 (Swine-Origin) Influenza A Virus
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Q. How can I avoid coming down with influenza (the flu) this year?
A. The best method of prevention is through vaccination. The seasonal influenza vaccine is currently available, and the Novel H1N1 vaccine will be available to select groups in mid to late October. Check with your health care provider to see if you and your family should receive the vaccine.
The other important preventative measure is frequent hand washing with either with soap and water, or an alcohol-based cleanser. Avoid touching your hands to your eyes, nose, and mouth unless you have first washed your hands, since infection is spread in this manner.
Q. How will I know that I have Novel H1N1 and not Seasonal Influenza?
A. As of September 2009, more than 99% of circulating influenza viruses in the United States are Novel H1N1. Therefore, at this time, if your health care provider determines that you have the flu, you most likely have Novel H1N1.
There are laboratory tests available that can tell the difference between Novel H1N1 influenza and other strains. The CDC has recommended that this testing be focused on people who are hospitalized with suspected flu and people such as pregnant women or people with weakened immune systems, for whom a diagnosis of flu will help their doctor make decisions about their care.
Q. If I do come down with the flu, how can I avoid spreading it to others?
A. Infectious virus is released by coughing and sneezing, and can be spread on contaminated hands and objects. Therefore, wash your hands frequently, cover your mouth and nose with a tissue when you cough and sneeze, throw used tissues away immediately, and limit contact with others. The CDC recommends staying at home while you are infectious to others. Infected persons are thought to be infectious from the day before onset of illness until the resolution of fever (up to 7 days after onset). People that are immunocompromised and young infants may be infectious even longer.
Q. Should laboratory workers get the Novel H1N1 vaccine?
A. Yes, unless there are contraindications to receiving the vaccine. Health care workers are one of the groups that are targeted for initial vaccination since illness and absenteeism negatively impacts the capacity of the health care system. If laboratory workers have patient contact, they can also potentially spread infection to vulnerable patient groups.
Q. What are the recommended tests for Novel H1N1 influenza A virus?
A. There are several options for detection of Novel H1N1 and other influenza viruses, and not all are suited for every laboratory setting.
Rapid antigen diagnostic tests (RIDTs), also known as card tests, are widely available and can be performed in the clinical setting or laboratory by trained personnel. Some commercially available tests can distinguish between influenza A and B viruses, and most can detect the Novel H1N1 virus, but none are able to provide the specific subtype of the virus detected. Also, the sensitivity and specificity of these tests vary widely, and negative results should be confirmed by an alternative method such as PCR if there is a clinical suspicion of infection. The CDC states:
“If clinical suspicion of influenza is high in a patient who tests negative by RIDT, empiric antiviral therapy should be administered, if appropriate, and infection control measures implemented.”
Real-time reverse transcription PCR (rRT-PCR) is currently the recommended test for confirmation of influenza A cases. There are a limited number of PCR tests available for subtyping the influenza A viruses (eg CDC swine panel), but the release of several commercial tests is anticipated in the coming months.
Other test options include immunofluorescence-based tests (DFA or IFA) and viral culture. Immunofluorescence can provide relatively rapid, accurate identification of influenza A and B viruses, but requires a high quality clinical specimen and a trained, experienced operator. Viral culture can also detect influenza A and B viruses, but may not yield timely results for clinical management. Neither can currently provide subtype identification of the Novel H1N1 virus.
Q. What is a good source for finding up-to-date information on influenza A and the Novel H1N1 subtype?
A. The CDC website (http://www.cdc.gov/h1n1flu/) is continuously updated and provides a wealth of information on Influenza A infection and the Novel H1N1 virus.