My previously healthy patient developed a viral illness with fever and headache few days after swimming in a community pool. Can swimming pools be a source of viral infection?

Yes! Swimming pools have been implicated in the transmission of a variety of pathogens,  including enteric viruses (eg, echovirus, coxackie virus, hepatitis A virus, norovirus) which account for nearly one-half of all swimming pool-related outbreaks.  Adenoviruses also account for a significant number of swimming pool outbreaks.1,2

The most commonly reported symptoms in swimming pool outbreaks have been gastroenteritis, respiratory symptoms and conjunctivitis. However, aseptic meningitis and hepatitis may also occur. 1

Because viruses cannot replicate in the environment outside of host tissues, their presence in swimming pool is the result of direct contamination by those in the water who may shed viruses through unintentional fecal release or through body fluids, such as saliva, mucus, or vomitus.  The finding of E. coli in 58% of pool water samples in 1 CDC study suggests the presence of stool as a primary source of infection.3

On average, each person has 0.14 grams (range 0.1 gram to 10 grams) of fecal material on their perianal surface that could rinse into the water if pre-swim shower with soap is omitted.4-5 Coupled with the potential for inadequate disinfection or chlorination of pool water, it is not surprising that swimming pools may serve as a source of infection.  

CDC recommends keeping feces and urine out of the water, checking the chlorine level and pH before getting into the water and not swallowing the water you swim in.3 

Bonus pearl: Did you know that pool water has also been associated with Cryptosporidium and Giardia and waterslides with E.coli-0157 outbreaks?

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References

  1. Bonadonna L, La Rosa G. A review and update on waterborne viral diseases associated with swimming pools. Int j Environ Res Public Health 2019;16, 166. Doi:10.3390/ijerph16020166. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6352248/
  2. Keswick BH, Gebra CP, Goyal SM. Occurrence of enteroviruses in community swimming pools. Am J Public Health 1981;71:1026030. https://www.ncbi.nlm.nih.gov/pubmed/6267950
  3. CDC.Microbes in pool filter backwash as evidence of the need for improved swimmer hygiene—Metro-Atlanta, Georgia, 2012. MMWR 2013;62:385-88. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6219a3.htm
  4. Gerba CP. Assessment of enteric pathogen shedding by bathers during recreational activity and its impact on water quality. Quant Microbiol 2000; 2:55-68 https://arizona.pure.elsevier.com/en/publications/assessment-of-enteric-pathogen-shedding-by-bathers-during-recreat
  5. CDC. Model Aquatic Health Code. 8.0 Annexes: fecal/vomit/blood contamination response Annex (6.0 policies and management), 2008. https://www.cdc.gov/healthywater/pdf/swimming/pools/mahc/structure-content/mahc-fecal-vomit-blood-contamination-response-annex.pdf
  6. CDC. Surveillance of waterborne disease outbreaks and other health events associated with recreational water—United States, 2007-2008 and surveillance of waterborne disease outbreaks associated with drinking water—United States, 2007-2008. MMWR 2011;60. 1-76. https://www.ncbi.nlm.nih.gov/pubmed/21937976

 

 

My previously healthy patient developed a viral illness with fever and headache few days after swimming in a community pool. Can swimming pools be a source of viral infection?

My patient with erythema multiforme has tested positive for Mycoplasma pneumoniae IgM antibody. Does this mean she has an acute M. pneumonia infection as the cause of her acute illness?

Not necessarily! Although detection of IgM in the serum of patients has proven valuable in diagnosing many infections during their early phase, particularly before IgG is detected, less well known is that false-positive IgM results are not uncommon. 1

More specific to M. pneumoniae IgM, false-positive results have been reported in 10-80% of patients without a clinical diagnosis of acute M. pneumoniae infection 2-4 and 3-15% of blood donors. 4

False-positive IgM results may also occur when testing for other infectious agents, such as the agent of Lyme disease (Borrelia burgdorferi), arboviruses (eg, Zika virus), and herpes simplex, Epstein-Barr, cytomegalovirus, hepatitis A and measles viruses. 1,5  

Reports of false positive IgM results include a patient with congestive heart failure and mildly elevated liver enzymes who had a false-positive hepatitis IgM which led to unnecessary public health investigation and exclusion from an adult day care center. 1 Another patient with sulfa rash had a false-positive measles IgM antibody resulting in callback of >100 patients and healthcare providers for testing!5

There are many potential mechanisms for false-positive IgM results, including polyclonal B cell activation, “vigorous immune response”, cross-reactive antibodies, autoimmune disease, subclinical reactivation of latent viruses, influenza vaccination, overreading weakly reactive results, and persistence of antibodies long after the resolution of the acute disease. 1,2

In our patient, a significant rise in M. pneumoniae IgG between acute and convalescent samples several weeks apart may be more helpful in diagnosing an acute infection accounting for her erythema multiforme.

 

References

  1. Landry ML. Immunoglobulin M for acute infection: true or false? Clin Vac Immunol 2016;23:540-5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4933779/
  2. Csango PA, Pedersen JE, Hess RD. Comparison of four Mycoplasma pneumoniae IgM-, IgG- and IgA-specific enzyme immunoassays in blood donors and patients. Clin Micro Infect 2004;10:1089-1104. https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(14)63853-2/pdf
  3. Thacker WL, Talkington DF. Analysis of complement fixation and commercial enzyme immunoassays for detection of antibodies to Mycoplasma pneumoniae in human serum. Clin Diag Lab Immunol 2000;7:778-80. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC95955/
  4. Ryuta U, Juri O, Inoue Y, et al. Rapid detection of Mycoplasma pneumoniae IgM antibodies using immunoCard Mycoplasma kit compared with complement fixation (CF) tests and clinical application. European Respiratory Journal 2012; 40: P 2466 (Abstract). https://erj.ersjournals.com/content/40/Suppl_56/P2466 
  5. Woods CR. False-positive results for immunoglobulin M serologic results: explanations and examples. J Ped Infect Dis Soc 2013;2:87-90. https://www.ncbi.nlm.nih.gov/pubmed/26619450

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My patient with erythema multiforme has tested positive for Mycoplasma pneumoniae IgM antibody. Does this mean she has an acute M. pneumonia infection as the cause of her acute illness?