BREAKING! Asymptomatic COVID-19 Infections Found to Quietly Damage Male Fertility Without Any Warning Signs

Medical News: While most people have now moved on from worrying about COVID-19, new research has revealed that men who were infected with SARS-CoV-2 but showed no symptoms at all may not be in the clear. A groundbreaking study conducted by Chinese researchers has shown that even asymptomatic COVID-19 infections can cause significant disruptions to male reproductive health, particularly by altering the protein composition in seminal plasma and reducing overall semen quality.


Asymptomatic COVID-19 Infections Found to Quietly Damage Male Fertility Without Any Warning Signs

The study was led by scientists from several prestigious institutions in China including the Center for Reproductive Medicine and the Jiangxi Key Laboratory of Reproductive Health at Jiangxi Maternal and Child Health Hospital in Nanchang Medical College, the Reproductive and Genetic Hospital at the University of Science and Technology of China in Hefei, the Center for Reproductive Medicine at Tangdu Hospital of Air Force Medical University in Xi’an, and the Bright Prosperity Institute in Hangzhou. What makes these findings especially alarming is that the infected men in the study experienced no fever, cough, fatigue, or other typical COVID-19 symptoms - yet their reproductive systems were silently suffering. This Medical News report highlights how the virus, though seemingly harmless in its asymptomatic form, may have long-term consequences on fertility and reproductive potential in males.
 
Total Sperm Count Drops After Infection
Researchers recruited healthy, non-smoking males aged 20 to 40 who were planning to undergo assisted reproductive treatment due to female infertility issues. The study participants were divided into two groups: 11 men who tested positive for SARS-CoV-2 but exhibited no symptoms, and a control group of 7 uninfected men. Semen samples were collected before and after infection to track any physiological changes.
 
The most striking finding was the significant drop in total sperm count after asymptomatic infection. For example, in one cohort, the average sperm count fell from 276.7 million to just 111.5 million after infection. Another group showed a similar decline - from 254.4 million to 81.1 million. Semen volume and sperm concentration also saw notable reductions. Surprisingly, viral RNA was not detected in any semen samples, suggesting the testicles themselves weren’t directly infected but were still negatively affected.
 
Proteins in Seminal Plasma Disrupted
Using a technique known as label-free quantitative proteomic profiling, researchers analyzed the protein composition of the seminal plasma from both groups. They identified 733 distinct proteins, of which 37 were significantly altered in the COVID-19 group. Specifically, 23 proteins were upregulated, and 14 were downregulated.
 
These proteins play crucial roles in sperm development, immune responses, inflammation, and oxidative stress. For instance, one protein, intelectin-1 (ITLN1), which is linked to inflammation and known to be elevated in infertile men, was found in higher amounts after COVID-19 infection. Another important protein, glutathione S-transferase mu 2 (GSTM2), which helps defend sperm against oxidative damage, was significantly reduced. The altered proteins were further validated by Western blot analysis, confirming that the infection led to substantial biochemical changes even without causing symptoms.
 
Reproductive Function Pathways Affected
The researchers conducted further analysis using internationally recognized tools like Gene Ontology (GO), the Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome. These analyses revealed that the differentially expressed proteins were highly enriched in pathways linked to inflammation, immune responses, and sperm production.
 
Key reproductive processes such as spermatogenesis (sperm formation), spermatid development, and sperm differentiation were among the most affected. There was also an increase in proteins involved in stress responses, particularly heat shock proteins like HSP90, which are typically elevated during infection or physical stress. These findings suggest that asymptomatic infection doesn’t just cause a temporary imbalance but may interfere with the body’s long-term reproductive processes at a molecular level.
 
How COVID-19 Alters the Male Reproductive Microenvironment
Although the blood-testis barrier likely prevented the virus from entering the testes directly, the systemic immune response caused by COVID-19 seems to have changed the environment in which sperm are produced and maintained. This disruption led to altered protein levels and may ultimately impair sperm quality.
 
The study’s correlation analysis also found that some proteins - especially CLSTN1 - were negatively associated with key sperm parameters like motility and concentration. The presence of such proteins in higher levels could signal sperm damage or stress, even in the absence of direct viral invasion.
 
Key Signaling Pathways Impacted
One of the most notable molecular pathways found to be affected was the PI3K-AKT pathway. This pathway is essential for the development of sperm cells, sperm motility, and hormone regulation. Disruption here could have cascading effects on male fertility. The research also pointed out changes in protein phosphorylation levels, which are critical for regulating cellular functions including sperm energy production and mobility.
 
Other important proteins affected include ECM1 and IPO5, which are involved in maintaining tissue structure and assisting the transport of critical molecules within cells - both vital for healthy sperm development.
 
Heat Shock Proteins and Other Key Biomarkers
Several heat shock proteins (HSPs) were found to be elevated, including HSPA1B, HSPA2, and HSP90AB1. These proteins typically respond to cellular stress and can disrupt sperm development if overexpressed. In previous clinical studies, increased HSP levels were linked to lower sperm count and fertility problems.

Other markers like CCT8 and RUVBL1, which are associated with immature sperm cells and DNA repair, were also found at higher levels after infection, suggesting further stress and possible damage to the reproductive system.
 
Conclusion
This important study offers compelling evidence that even asymptomatic COVID-19 infections can negatively impact male reproductive health by altering the seminal plasma proteome and reducing sperm quality. A total of 37 key proteins were identified as differentially expressed, many of which are involved in inflammation, immunity, oxidative stress, and sperm development. While the virus did not directly enter the testicles, its effects on the systemic immune system and protein pathways caused significant disruptions.
 
These findings should be a wake-up call for both physicians and public health authorities. Men who have had COVID-19, even without symptoms, should consider getting their fertility assessed - especially if they are planning to start a family. Further research is urgently needed to understand the long-term impacts and whether these changes are reversible. In the meantime, it is critical to recognize that the absence of symptoms does not mean the virus is harmless, particularly when it comes to reproductive health.
 
The study findings were published in the peer reviewed journal: BMC Genomics.
https://bmcgenomics.biomedcentral.com/articles/10.1186/s12864-025-11473-5
 
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Read Also:
https://www.thailandmedical.news/news/emergence-of-antisperm-antibodies-causing-infertility-issues-in-men-who-had-covid-19-infections-or-vaccines
 
https://www.thailandmedical.news/news/covid-19-causes-testicular-inflammation-leading-to-testicular-tissue-damage-and-decreased-fertility
 
https://www.thailandmedical.news/news/study-warns-that-covid-19-is-affecting-semen-quality
 
https://www.thailandmedical.news/news/breaking-covid-19-news-argentinian-scientists-warn-that-asymptomatic-sars-cov-2-infections-can-lead-to-persistent-oligonecrozoospermia-in-men
 
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