Most viral infections come and go, but some quietly stay in the body for life and can resurface years later. A recent genetic analysis of over 900,000 people offers new clues into why this happens, and what it could mean for long-term health.
The study, “The DNA virome varies with human genes and environments”, published in the journal Nature, maps how viral loads change across a lifetime and reveals that our genes, immune system and even habits may shape whether viruses linger or fade away.
What did the study look at?
Researchers analysed viral DNA found in blood and saliva samples across large biobanks – the UK Biobank, the National Institutes of Health’s All of Us Research Program, and Simmons Foundation Powering Autism Research for Knowledge, focusing on common viruses that often stay in the body after infection.
Key viruses studied included:
Epstein-Barr virus, linked to certain cancers and autoimmune diseases
Human herpesviruses (HHV-6 and HHV-7)
Merkel cell polyomavirus
Anelloviruses, which are widespread and often harmless
“We’re getting to the point now where we can use human genetics to try to answer fundamental questions about pathology resulting from viruses,” including whether a virus is likely to play a role in causing cancer or other diseases later in life, said first author Nolan Kamitaki, research fellow in genetics in the Blavatnik Institute at Harvard Medical School (HMS).
Why do some viruses linger?
The findings suggest there is no single answer, but rather a combination of biology and behaviour.
The immune system plays a central role. Some viruses evade immune detection or establish latency, allowing them to persist for life. The study found that genetic differences affecting immune responses strongly influence how well the body controls viral load.
Your genes may decide the outcome. Dozens of genetic factors were linked to the amount of virus remaining in the body. These genes often regulate immune pathways or how infected cells escape destruction.
“It’s amazing how much DNA can teach us about dynamic biological processes and the ways in which our habits, our genes, and our biology shape those processes,” said Steven McCarroll, co-senior author and professor of biomedical science and genetics at HMS.
Viruses behave differently across life stages. Each virus follows its own pattern. Some of them peak in early childhood after the first infection, while others, like the Epstein-Barr virus, increase with age. Meanwhile, some decline as the immune system gains control over time.
Patterns uncovered by the study
Beyond persistence, the research revealed striking variations influenced by lifestyle and environment.
Men had consistently higher viral loads than women across all viruses
Smoking increased Epstein-Barr viral load, nearly doubling it in heavy smokers
Seasonal shifts were observed, with some viruses rising in winter and others in summer
These patterns highlight how everyday factors interact with biology in shaping viral behaviour.
What does this mean for long-term health?
Persistent viruses are not always harmless. While many remain dormant, some are linked to serious conditions later in life.
Epstein-Barr virus is associated with multiple sclerosis and certain cancers
The study found that higher viral load may increase the risk of Hodgkin lymphoma, although more research is needed
The risk of multiple sclerosis may depend more on the immune response than the viral load itself
This distinction could be crucial for future therapies.
Why this research matters
This is one of the largest studies to map the human DNA virome, offering a deeper understanding of how viruses and humans coexist over decades. Key takeaways include:
Viral persistence is shaped by genetics, immunity and environment
Not all long-term viruses behave the same way
Measuring viral load over time could help predict disease risk
Researchers say such insights could eventually guide personalised medicine, where an individual’s genetic profile helps predict how their body handles infections.
And as large-scale genetic data becomes more accessible, scientists are getting closer to understanding not just how infections begin, but also how they quietly shape health across a lifetime.
This report is for informational purposes only and is not a substitute for professional medical advice.
