Can my patient contract influenza more than once in a season?

It’s not common but reinfection with influenza can definitely occur, either due to the same viral strain, or due to a different one altogether.

One study reported influenza reinfection due to H1N1 in otherwise healthy patients within 12-20 days of the original infection after an apparent period of full recovery. 1 There was no evidence of resistance to oseltamivir among isolates and all patients recovered after the second infection.

Reinfection with the same viral strain within 2-3 weeks of the initial bout of influenza shouldn’t be too surprising since it takes 4-7 weeks for antibody response to the infection to peak. 2 Reexposure to the same circulating strain of influenza virus (the season can last 6 weeks or longer) can then result in reinfection when the body hasn’t had enough time to make significant amount of protective antibodies following the first infection.

Another explanation is that more than 1 strains of influenza virus often circulate during any given season.   This places patients at risk of infection due to strains of influenza virus that do not confer significant cross-immunity between each other,  resulting in getting “the flu twice in 1 season.” 3

References

  1. Perz CM, Ferres M, Labarca JA. Pandemic (H1N1) 2009 reinfection, Chile. Emerg Infect Dis 2010;16:156-57. https://wwwnc.cdc.gov/eid/article/16/1/pdfs/09-1420.pdf
  2. Treanor JJ. Influenza viruses, including avian influenza and swine influenza. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and practice of infectious diseases. 7th ed. New York: Elsevier; 2010. p 2265-2293.
  3. Rettner R. Can you get the flu twice in 1 season? Scientific American, LiveScience, February 4, 2018. https://www.scientificamerican.com/article/can-you-get-the-flu-twice-in-1-season/ . Accessed February 5, 2018.

 

Can my patient contract influenza more than once in a season?

My 65 year old patient has had several bouts of bacterial pneumonia in the past 2 years. Her total serum immunoglobulins are within normal range. Could she still be immunodeficient?

Absolutely! Besides HIV infection which should be excluded in all patients with recurrent bouts of bacterial pneumonia irrespective of age, “selective polysaccharide antibody deficiency”, also known as “specific antibody deficiency” or SAD, should also be excluded (1-3). SAD in adults with recurrent pneumonia is not rare, having been reported in about ~8% of such patients (4).  

Think of SAD when your adult patient presents with recurrent bouts of bacterial pneumonia  despite having normal serum total immunoglobulin (IgG, IgA, and IgM) levels and IgG subtypes (1-3).  These patients have a normal response to tetanus toxoid (a protein) but cannot mount adequate antibody response against polysaccharide antigens of pathogens such as pneumococcus.  

One way to diagnose SAD in a suspected patient is through vaccination with 23-valent pneumococcal polysaccharide vaccine (PPSV23).  In patients with low baseline antibody titers to many of the capsular types of pneumococcus included in the PPSV23,  a suboptimal response (defined by the lab) 4 weeks after vaccination with PPSV23 is suggestive of SAD. Remember that if your patient has already been vaccinated with the 13 valent pneumococcal conjugate vaccine (PCV13), you can only evaluate for the response to serotypes included in the  PPSV23 only.

Although there are no randomized-controlled studies and treatment should be individualized, immunoglobulin replacement may reduce the risk of future bouts of pneumonia in SAD (2-3). 

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References

1. Cohn JA, Skorpinski E, Cohn JR. Prevention of pneumococcal infection in a patient with normal immunoglobulin levels but impaired polysaccharide antibody production. Ann Allergy Asthma Immunol 2006;97:603-5. https://www.ncbi.nlm.nih.gov/pubmed/17165266

2. Cheng YK, Kecker PA, O’Byrne MM, Weiler CR. Clinical and laboratory characteristics of 75 patients with specific polysaccharide antibody deficiency syndrome. Ann Alergy Asthma Immunol 2006;97:306-311. https://www.ncbi.nlm.nih.gov/pubmed/17042135

3. Perez E, Bonilla FA, Orange JS, et al. Specific antibody deficiency: controversies in diagnosis and management. Front Immunol 207;8:586. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5439175/pdf/fimmu-08-00586.pdf

4. Ekdahl K, Braconier JH, Svanborg C. Immunoglobulin deficiencies and impaired immune response to polysaccharide antigens in adult patients with recurrent community acquired pneumonia. Scand J Infect Dis 1997;29:401-7. https://www.ncbi.nlm.nih.gov/pubmed/9360257

 

My 65 year old patient has had several bouts of bacterial pneumonia in the past 2 years. Her total serum immunoglobulins are within normal range. Could she still be immunodeficient?