The coordinator of a UK Long COVID group asked me to research and post on this topic. Endometriosis is one form of infertility that has a prevalence around 7%. When I checked the US National Library of Medicine for Endometriosis and microbiome, I found 88 studies most published in 2021 and later. It is a newly discovered association. I have added it to my PubMed Study page with bacteria listed here and a priori changes of diet to counter these shifts listed here.

I repeated searching the US National Library of Medicine for Endometriosis and microbiome for endometriosis and COVID. I found 66 studies — a volume that surprised me! A few studies that appear interesting:

• Patients with endometriosis may experience worse clinical manifestations and therapeutic outcomes during COVID–19 in western China- a case series comparative analysis. [2023] . We know from other studies that the microbiome determines the severity of COVID; thus having an altered microbiome (from endometriosis) is likely to be a contributor.
• Association of laparoscopically-confirmed endometriosis with long COVID–19: a prospective cohort study. [2023]. We know that long COVID has an altered microbiome and it would not be unexpected that some alterations would predispose some people to endometriosis by the microbiome alterations.
• COVID–19 susceptibility in endometriosis patients: A case control study. [2022] “women with endometriosis had a higher frequency of COVID-19 than the control subjects (23% vs. 13.5%), with a greater prevalence of fever (14.4% vs. 6%) and myalgias or arthralgias (11.4% vs. 4.5%)”
• A review on human reproductive systems encountering with the severe acute respiratory syndrome coronavirus 2 infection. [2023] which reports “female reproductive failures (polycystic ovary syndrome and endometriosis) increases the susceptibility to COVID-19.”
• The effect of SARS–CoV–2 BNT162b2 vaccine on the symptoms of women with endometriosis. [20223] reports “worsening in dysmenorrhea in the endometriosis patient group (39% vs 15%)

Concurrence between Microbiome Shifts

From the database I compared shifts between COVID and endometriosis, with the shift in common shown below.

Tax Name	Tax Rank	Shift
Coriobacteriaceae	family	High
Enterobacteriaceae	family	High
Atopobium	genus	High
Bacteroides	genus	High
Bifidobacterium	genus	High
Blautia	genus	High
Campylobacter	genus	High
Candida	genus	High
Corynebacterium	genus	High
Dialister	genus	Low
Escherichia	genus	High
Faecalibacterium	genus	High
Lachnospira	genus	Low
Lactobacillus	genus	Low
Odoribacter	genus	Low
Parabacteroides	genus	High
Paraprevotella	genus	Low
Prevotella	genus	High
Pseudomonas	genus	High
Ruminococcus	genus	Low
Shigella	genus	High
Streptococcus	genus	High
Eubacteriales	order	Low
Actinobacteria	phylum	High
Firmicutes	phylum	High
Proteobacteria	phylum	High
Verrucomicrobia	phylum	High

Can COVID cause Endometriosis

There is no clear evidence of that, but the table of common shifts implies that it is a reasonable hypothesis. Looking at numbers from Long COVID groups, you may see over representation (above the 7% expected). Endometriosis increased the odds (almost double) of getting COVID then seeing 14% of Long COVID population with Endometriosis could be explain by the increase risk of getting COVID.

On the brighter side, we now see that endometriosis has a significant microbiome dimension and thus treatment by microbiome manipulation becomes an option worth exploring.