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COVID-19

The illness caused by the SARS-CoV-2 coronavirus.

Compared within 3 studies that had both: 259 people with COVID-19 and 190 healthy people. 100 microbes are less common in people with COVID-19, and 12 more common.

A difference is an association: it doesn’t mean these microbes cause, prevent or treat COVID-19.

Phylum

Searching opens both lists and shows only matching rows.

Less common in COVID-19 · 100

Strongest first, then the biggest gap · Each figure is 10 people Strongest first · Each figure is 10 people
  1. Romboutsia timonensis in 3 studies Healthy 62% COVID-19 26%
  2. Roseburia faecis in 3 studies Healthy 70% COVID-19 34%
  3. Faecalibacterium prausnitzii in 3 studies Healthy 94% COVID-19 72%
  4. Allisonella histaminiformans in 3 studies Healthy 41% COVID-19 15%
  5. Ruminococcus sp. AF13-28 in 3 studies Healthy 68% COVID-19 39%

More common in COVID-19 · 12

Strongest first, then the biggest gap · Each figure is 10 people Strongest first · Each figure is 10 people
  1. Staphylococcus epidermidis in 3 studies Healthy 0% COVID-19 5.0%
  2. Oribacterium asaccharolyticum in 3 studies Healthy 0% COVID-19 4.2%
  3. Enterocloster aldenensis in 3 studies Healthy 39% COVID-19 60%
  4. Thomasclavelia ramosa in 3 studies Healthy 45% COVID-19 63%
  5. Enterocloster clostridioformis in 3 studies Healthy 21% COVID-19 37%

As many carry these · 5 the amount differs

Strongest first, then the biggest gap · Each figure is 10 people Strongest first · Each figure is 10 people
  1. Parabacteroides distasonis in 3 studies Healthy 84% COVID-19 86%

    Carriers have about 5 times as much, in 3 of 3 studies (0.11% → 0.52% of their gut microbes).

  2. Bacteroides uniformis in 3 studies Healthy 91% COVID-19 86%

    Carriers have about twice as much, in 3 of 3 studies (0.32% → 0.78% of their gut microbes).

  3. Flavonifractor plautii in 3 studies Healthy 82% COVID-19 83%

    Carriers have about twice as much, in 3 of 3 studies (0.09% → 0.17% of their gut microbes).

Where these numbers come from

Studies
Only GMrepo projects that had people with the condition and healthy people, 10 or more of each. Numbers come from those studies, never from pooling.Sampled in China, Japan.
How common
The share of people whose sample has any of it, in the people with the condition and in the healthy people of those same studies. Tested within studies (Cochran–Mantel–Haenszel, corrected for testing many microbes); a difference counts when it is clear and meaningful (Cohen’s h of 0.2 or more).
Strength word
Counted by code from how many studies point the same way: Seen again and again (3 or more, none clearly the other way), Seen more than once (2, the majority), Seen once (1, listed last). Where studies disagree, a row isn’t listed.
Each study
Tap a row for every study’s own numbers, and for how much carriers have.
Analysis
Our analysis of GMrepo data. GMrepo on Data sources · Read the rules

Also compared · 465 microbes

Compared within studies that had both, but not listed above.

No meaningful difference · 465
PubMed · human studies and reviews first

Recent research

All research on it
  1. Observational BMC microbiology · 2026
    Molecular and phenotypic profiles of carbapenem- and third-generation cephalosporin-resistant Klebsiella pneumoniae isolates from the fecal microbiota of pediatric patients with COVID-19.
    PubMed ↗
  2. Review International journal of molecular sciences · 2025
    Microbiome and Long COVID-19: Current Evidence and Insights.
    PubMed ↗
  3. Randomized trial The journal of contemporary dental practice · 2025
    Oral Probiotic Containing Streptococcus salivarius K12 and Lactobacillus brevis CD2 for Preventing Bacterial Pneumonia in Severe COVID-19: Randomized Clinical Trial.
    PubMed ↗
  4. Observational MicrobiologyOpen · 2025
    Examine the Impact of Self-Medicated Antibiotics on Gut Bacterial Diversity From COVID-19 Patients in Gopalganj, Bangladesh.
    PubMed ↗
  5. Meta-analysis International journal of medical sciences · 2025
    Association Between Gut Microbiota and Pneumonia Risk: A Systematic Review and Mendelian Randomization.
    PubMed ↗

Source: PubMed, U.S. National Library of Medicine · 113 linked papers, last 10 years