Not everyone who becomes infected with INFLUENZA gets sick. We don’t need any special molecular approach to detect influenza when people got really sick. But many people may feel good even if they are infected. I would assume they are competent hosts. Can anyone suggest molecular methods to detect the presence of influenza virus in human body?
Influenza is either diagnosed by RT-PCR assay from nasopharyngeal swabs from patients with clinical influenza symptoms, by serological testing or by clinical grounds alone. The WHO recommended molecular diagnostics (RT-PCR) to be the “gold standard” for diagnosing A(H1N1)pdm09. The RT-PCR test can distinguish between different subtypes of influenza. Point-of-care tests (rapid influenza antigen immunoassay) have also been developed, but the usefulness of those test kits is questionable as the sensitivity is low. Serological testing is not useful in a clinical setting as it is necessary to obtain serum in the acute phase of the disease and a control later (usually in 10-14 days) to be able to detect raise in titre. However, for population studies and to evaluate vaccine efficacy it is of great value. Increase in titre from baseline or in unexposed individual are either due to past infection or due to immunization. So, it is possible to detect evidence of previous infection.
Asymptomatic shedding of influenza has been detected by PCR on Nasopharyngeal swabs. the problem is convincing someone to give a swab test every week for the duration of a study...
some other studies have looked at fecal samples also...
As Kristian mentioned rapid antigen test have low usefulness as sensitivity is low even in sick cases. so I would recommend them.
Dear Kristian,
Thanks a lot for your kind and most detailed reply. Could you please suggest me some most important papers on the methods you mentioned? It will take me some time to figure out what is best approach for my future research. Thank you very much once again! I am very happy about your reply.
Best regards,
Indrikis
Dear Bruno,
Thank you very much for your message. It is interesting to hear that some people tried to look at fecal samples to detect influenza. Could you tell me please what are those studies? Thank you very much once more for your excellent message.
Best regards,
Indrikis
Hi Indrikis, will look for those paper and send you the information. regarding PCR diagnosis... check the cdc web page. they update their primers according to what is circulating ( i remember some changes after the last pandemic H1N1)
Just one example
Seasonal Influenza A Virus in Feces of Hospitalized Adults
http://wwwnc.cdc.gov/eid/article/17/11/11-0205_article
Hi Bruno,
Excellent! Thank you very much! I might be back after reading that article.
Best regards,
Indrikis
Concerning serology, this is the classic paper to describe that methods:
Hobson D, Curry RL, Beare AS, Ward-Gardner A. The role of serum haemagglutination-inhibiting antibody in protection against challenge infection with influenza A2 and B viruses. J Hyg (Lond) 1972;70:767-77.
Yes, it is an old paper, but still used as the primary article referring that method.
Good luck with your study!
Kristian.
Just to point out that we are talking about influenza "A". I asume that you want to detect, regardless of subtype (H1, H3 ...). In that case it is best to prioritize the sensitivity offered by the M gene-based PCR (highly conserved in all type A subtypes) in a real-time platform, then you can determine the subtype of the virus by a multiplex PCR.
Other studies will require isolation (not just detection).
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