Flu and COVID-19 May Wake Dormant Cancer Cells, New Research Finds
New findings suggest that respiratory infections—like the flu or COVID‑19—combined with poor sleep can have unexpected consequences: they may reawaken dormant cancer cells, increasing the risk of metastatic relapse. This is an emerging area of concern for cancer survivors, especially those who’ve been in remission for breast cancer.
A study published in Nature found that viral infections in the lungs can trigger dormant cancer cells to become active. In mouse models, infections such as influenza or SARS‑CoV‑2 revealed tumor cells hidden in the lungs and accelerated the development of metastatic tumors. Epidemiological data from breast cancer survivors further confirmed a nearly two‑fold increase in lung metastasis among those who tested positive for COVID‑19.
In short, lung infections create an inflammatory environment that prompts immune cells like neutrophils, a type of white blood cell, to release molecules that disturb dormant tumors. This microbial stimulus can cause cancer cells that had remained dormant for years to re‑start growth and begin to spread.
Why Sleep Matters for Immunity—and Cancer Risk
Sleep isn’t just rest—it’s a critical pillar of immune health. Chronic lack of sleep weakens the body’s defenses, raising both infection risk and severity. According to research summarized in The Lancet, poor sleep is linked to more severe respiratory infections, including COVID‑19 and flu.
Another NIH‑supported study found that consistent, quality sleep supports the proper development of monocytes—white blood cells essential for immune surveillance and inflammation control. Without adequate rest, these immune cells may become improperly regulated, compromising defenses against infections and possibly cancer progression.
A deeper review in MDPI found evidence showing that poor or disrupted sleep is linked to higher cancer risk and worse outcomes. Insufficient sleep affects multiple bodily systems—including hormone balance, inflammatory signaling, and immune regulation—potentially enabling cancer cells to slip past surveillance and grow unchecked.
Connecting the Dots: Infection, Sleep and Relapse
Here’s how the information found in these studies relate to each other:
Respiratory infections like flu or COVID‑19 create lung inflammation.
This inflammation can rouse dormant cancer cells, especially in the lungs.
Chronic poor sleep undermines the immune system’s ability to regulate inflammation and control cell behavior.
Combined, these conditions may increase the risk of dormant tumors reactivating.
Sleep deficiencies also impair the immune system’s ability to fight infection, meaning infections may linger or become more severe, which amplifies inflammation and leads to a cascade of events that could prompt cancer cells to wake up.
What Cancer Survivors Should Know
Vaccination remains essential. Flu and COVID‑19 vaccines reduce infection risk and complications, especially crucial for individuals with past cancer.
Prioritize good sleep. Aim for seven to nine hours nightly, and maintain consistent bedtime routines. This helps maintain immune resilience and reduce infection severity.
Monitor symptoms closely. Respiratory infections in survivors should be reported and treated promptly to limit inflammation.
Regular follow-up care is vital. Imaging and screening can help catch early signs of metastasis before symptoms appear.
What Researchers Plan Next
The recent Nature findings focus mainly on breast cancer survivors and lung tissue in mice—but similar processes may apply to other cancers. Research is underway to explore how infections affect dormant cancer cells in patients with other types of cancer and develop therapies that block inflammatory triggers associated with infections or poor sleep environments.
While overall relapse rates remain relatively low, these findings underscore a new risk factor for cancer survivors: the convergence of respiratory infections and chronic poor sleep. The science isn't yet conclusive—but taking preventive steps now could help reduce the chance of dormant cancer cells reawakening.
Survivors should speak with their doctors about flu and COVID‑19 prevention, and prioritize sleep wellness as part of post‑remission care.