mycobacterium-avium-showerhead

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Readers searching for mycobacterium avium showerhead information usually want one answer: can the water from a showerhead carry the bacteria behind a lung infection? Two peer-reviewed studies address that question directly. One sampled showerhead biofilm from 656 households in the United States and Europe. The other compared home samples from people with Mycobacterium avium complex lung disease with matched control homes. Neither shows that a shower caused an infection, and this guide explains what each one measured.

Quick answer

• Showerheads often carry mycobacteria. In the 2018 study, the authors report that “the genus Mycobacterium was consistently the most abundant genus of bacteria detected in residential showerheads”.
• Counts varied by water supply. “Mycobacteria were far more abundant, on average, in showerheads receiving municipal water than in those receiving well water”.
• In the 2020 case-control study, NTM were isolated from shower aerosols in case homes more often than in control homes. The adjusted odds ratio was 4.0, with a wide 95% confidence interval of 1.2 to 13.
• Neither study measured whether a shower caused an infection in a specific person.

What the 2018 showerhead study measured

Gebert and colleagues collected showerhead biofilm samples and water chemistry data with the help of citizen scientists. The study is an observational survey of household plumbing, not a study of people who were ill. The authors describe their analyses as “cultivation-independent”, which is the wording the abstract uses for the method.

The paper states that “Each participant was asked to provide the household address, the household water source, the estimated time since installation of showerhead, its usage frequency, cleaning frequency, and a description of the showerhead sampled (including materials and spray pattern).” The household answers are self-reported, so the water and usage details are only as accurate as each participant’s account.

The abstract states the main result in one sentence: “While most of these bacteria are innocuous, some are potential pathogens, including members of the genus Mycobacterium that can cause nontuberculous mycobacterial (NTM) lung infection”. The phrase “some are potential pathogens” is the important limit. The study identifies mycobacteria that could cause disease, and it does not show that any particular showerhead in the sample caused an infection.

Where the mycobacteria were highest

The abstract names water source and water chemistry as influences on which mycobacteria appear. Homes on municipal water had more mycobacteria in their showerheads than homes on well water. The authors also compared countries. Across the samples, “total chlorine concentrations in shower water in the United States were 11 times higher, on average, than those measured in shower water in the European households”.

The authors connect these differences to disinfection. They write that the differences are “likely driven by differences in the use of chlorine disinfectants”, and they note that mycobacteria are “significantly more resistant than other bacteria to chlorine”. Chlorine is added to municipal water to limit bacteria, so a homeowner on a municipal supply may see a different biofilm from one on a well. The paper does not show that any single water source is safe or unsafe for a given person.

The study also looked at location. The authors found geographic hot spots in the United States where showerheads had high abundances of potentially pathogenic lineages, and they report that these hot spots generally overlapped the regions where NTM lung disease is most prevalent. The paper is careful about what this means. In their words, “So far, our results are correlative”. The showerhead data were compared with state-level disease estimates, not with the illness of people in the sampled homes.

The authors add that the patterns can be anticipated to a degree. They write that “mycobacterial distributions in showerhead biofilms are often predictable from household location and water chemistry”. Predictable is not the same as proven, and the study does not test whether predicted high-count showerheads lead to more disease.

The 2020 case-control study on shower aerosols

Tzou and colleagues recruited Washington and Oregon residents who had been diagnosed with MAC pulmonary disease. Each case was matched for age, sex and geography to population controls. The team sampled five points in the home: bathroom faucets, kitchen faucets, shower aerosols, indoor soil and outdoor soil. The study had 56 case homes and 51 control homes.

The aerosol sample was taken where people shower. In the paper’s words, “Shower aerosols were collected from the bathroom most often used by the subject for showering or bathing.” The authors then compared the presence of NTM in each home with disease status.

The main result is that “NTM were isolated from shower aerosols collected in case homes more often than in control homes”. After adjustment, the authors report that NTM isolation from shower aerosols “had a high odds ratio associated with disease (odds ratio, 4.0; 95% confidence interval, 1.2–13)”. The interval is wide, which means the estimate is uncertain even though it points in one direction.

The other sites did not show the same pattern. The abstract says that “Other home environmental samples (tap water, soils) did not exhibit this association.” The authors conclude that “The results implicate shower aerosols as uniquely significant sources of NTM exposure in homes”. That conclusion is the authors’ interpretation of a 56-versus-51 home comparison, and it should be read with the limits below.

The authors list their own limits. They write that “Additional limitations were that the study was not powered to divide results into high, low, and no colonization”, and they add that “A larger study may have detected weaker associations between NTM and disease in point-of-use sources other than shower aerosols.” They also state a boundary on their claim: “we did not attempt to generate evidence that the species and strains of environmental mycobacteria isolated in our study were involved in initial MAC-PD infections.”

Who the studies describe as at risk

The 2020 paper describes host factors as the main story. It says that NTM pulmonary disease “has known host risk factors that include advanced age, thoracic structural anomalies, preexisting pulmonary disease, and autoimmune disease”. The same authors reported in an earlier analysis of their case-control data that “MAC-PD is strongly associated with host risk factors”. Their conclusion was that there was “more evidence that MAC-PD is a disease that affects” susceptible persons than evidence that it results from an unusual dose of organisms.

The 2018 study describes a similar group. Its introduction notes that NTM can cause “disseminated infections among susceptible individuals, including those with compromised immune systems”. The 2018 study sampled households and water, not patients, so this sentence is background from the literature rather than a finding about the sampled households.

The 2020 authors call for more work on “residential exposures, including but not limited to shower aerosols, in the homes of individuals with compromised immune or pulmonary systems”. That is a research recommendation. It does not establish a risk level for anyone, and it does not say how much exposure is needed for infection.

For a healthy reader, the sources do not describe a serious risk from a showerhead. They describe mycobacteria in showerheads and shower aerosols, and they describe the disease in people who are already susceptible. Readers with weakened immune systems, lung disease, or a history of lung infection should talk with a doctor about their own situation rather than rely on this guide.

What the sources say about cleaning

The sources checked do not give a cleaning method for showerheads, so this guide does not give one. The 2018 study asked households how often they cleaned the showerhead, but the paper does not report a cleaning method, and the sources checked do not report results by cleaning frequency. Any cleaning advice would go beyond what these studies state.

How we chose

This guide uses two sources, and both were opened and checked for the quotes used on 2026-10-28. Both are peer-reviewed journal articles that examine mycobacteria in showerheads or shower aerosols directly. The first is a survey of showerhead biofilm across 656 households. The second is a case-control study of home samples from people with MAC lung disease. Together they cover the two main questions readers ask: whether showerheads carry these bacteria, and whether shower aerosols are linked to disease in a comparison group.

No product is recommended. The sources do not test any showerhead, filter or cleaning product, and this guide does not name a brand.

What we could not verify

• Whether the regional overlap between showerhead mycobacteria and NTM lung disease reflects a link between showers and infection. The authors call their results correlative.
• Whether the 56 case homes and 51 control homes differed in exposures that the study did not sample.
• How often mycobacteria in shower aerosols would be found in homes outside the two states studied.
• How much shower exposure, if any, leads to disease. Neither study provides a dose-response measure.

What the sources do not say

The sources do not say how to treat or prevent NTM infection. They do not give a cleaning or disinfection method for showerheads, and they do not compare showerhead designs or materials. The sources also do not say how long it takes between exposure and disease, and they do not say whether households that changed their showerhead saw any change in their results.

The 2020 study compared homes, not other places a person might breathe mycobacteria, such as hospitals, workplaces or swimming pools. Its findings apply to the populations and regions it sampled, and they should not be stretched to other countries without new evidence.

FAQ

Can a showerhead carry mycobacteria?

Yes, according to the 2018 study. It found the genus Mycobacterium to be the most abundant bacterial genus in residential showerhead biofilm across its samples. Mycobacteria were more abundant in homes on municipal water than on well water, and in United States homes than in European homes.

Does a shower cause MAC lung disease?

The sources do not show that. The 2020 study found more NTM in shower aerosols in case homes than in control homes, but it does not establish that showering caused any person’s disease. The authors describe host risk factors as central to the disease.

Does chlorine make showerhead mycobacteria worse?

The 2018 authors say the higher counts in chlorinated water are “likely driven by differences in the use of chlorine disinfectants”. That is an association between water treatment and counts. The study does not test whether chlorine changes disease risk.

What cleaning method do the sources recommend?

None of the sources checked gives a cleaning method for showerheads. This guide does not offer one.

Should I be worried about my shower?

The studies describe possible exposure and a link in one comparison. They do not give an individual risk estimate. If you have weakened immune system function or lung disease, talk with a doctor before making decisions about your health.

Talk to a doctor

Readers with weakened immune systems, chronic lung disease, or a history of lung infection should talk with a doctor. A doctor can review symptoms, medical history and any test results, which these studies cannot do for an individual.

Bottom line

The studies support one firm point: mycobacteria are common in showerheads, and in one case-control study NTM in shower aerosols were more frequent in homes of people with MAC lung disease. They do not show how often a shower leads to infection, and the sources give no cleaning method. The studies do not describe a serious risk for healthy people, and they are a basis for further research rather than a verdict on any shower.

Sources

• Gebert MJ, Delgado-Baquerizo M, Oliverio AM, et al. “Ecological Analyses of Mycobacteria in Showerhead Biofilms and Their Relevance to Human Health.” mBio. 2018;9(5):e01614-18. https://pmc.ncbi.nlm.nih.gov/articles/PMC6212831/ (opened 2026-10-28)
• Tzou CL, Dirac MA, Becker AL, et al. “Association between Mycobacterium avium Complex Pulmonary Disease and Mycobacteria in Home Water and Soil: A Case-Control Study.” Annals of the American Thoracic Society. 2020;17(1):57-62. https://pmc.ncbi.nlm.nih.gov/articles/PMC6944351/ (opened 2026-10-28)