Respiratory illnesses such as COVID-19 and influenza are usually thought of as short-term infections that cause fever, cough, and fatigue. Most people recover within days or weeks. However, scientists are increasingly discovering that serious viral infections may leave long-lasting effects in the body.
A new study from researchers at the University of Virginia (UVA) suggests that severe respiratory infections may change the lungs in ways that could increase the risk of lung cancer later in life.
The research was carried out by scientists at UVA Health’s Beirne B. Carter Center for Immunology Research and the UVA Comprehensive Cancer Center. The study was led by Jie Sun, PhD, a scientist at the UVA School of Medicine.
The findings highlight a possible link between severe viral infections and the future development of lung cancer. At the same time, the researchers found encouraging evidence that vaccination may help prevent many of these harmful effects.
The lungs are delicate organs responsible for bringing oxygen into the body and removing carbon dioxide. They are constantly exposed to the outside environment through the air we breathe. Because of this, they are especially vulnerable to infections caused by viruses such as influenza and the coronavirus that causes COVID-19.
When someone experiences a severe respiratory infection, the lungs can become inflamed and damaged. Normally, the immune system works to repair this damage once the infection is over.
However, the new research suggests that in some cases the immune system may not return fully to normal. Instead, certain immune cells may remain in a state that promotes long-term inflammation.
According to Dr. Sun, this persistent inflammation may create an environment in the lungs that allows cancer to develop more easily months or even years after the original infection.
To better understand this process, the research team studied both laboratory mice and human health data. In experiments with mice, the scientists triggered severe lung infections and then observed the animals over time.
The results showed that mice that had experienced severe infections were more likely to develop lung tumors later. They were also more likely to die from lung cancer compared with mice that had not experienced such infections.
The researchers then looked at medical data from human patients to see whether a similar pattern existed. They found that people who had previously been hospitalized for COVID-19 showed a higher rate of lung cancer diagnoses compared with those who had not been hospitalized for the infection.
Their analysis showed about a 1.24-fold increase in lung cancer incidence among people who had been hospitalized due to COVID-19. Importantly, this increased risk appeared regardless of whether patients had other health problems or traditional lung cancer risk factors such as smoking.
These findings suggest that severe respiratory infections themselves may be an independent risk factor for lung cancer.
The researchers also wanted to understand what biological changes might explain this increased risk. Their experiments revealed major changes in several types of immune cells inside the lungs, especially neutrophils and macrophages. These cells normally play important roles in defending the body against infections.
However, after a severe infection, some of these immune cells appeared to behave differently. Instead of simply protecting the lungs, they helped maintain a state of ongoing inflammation. Scientists often describe this kind of environment as “pro-tumor,” meaning it can support the growth and survival of cancer cells.
The study also found changes in epithelial cells that line the lungs and the tiny air sacs responsible for oxygen exchange. Damage or abnormal repair of these cells could further contribute to conditions that allow tumors to develop.
One of the most encouraging findings from the research was the role of vaccination. The scientists observed that vaccination against respiratory viruses reduced the likelihood of the harmful lung changes linked to cancer development.
Vaccines help the immune system respond more effectively to infections, which often prevents the illness from becoming severe.
Because the increased cancer risk was mainly observed after severe infections, preventing severe disease appears to protect the lungs from the long-term inflammatory damage that may promote cancer.
The researchers noted that people who had only mild COVID-19 infections did not show the same increased risk. In fact, some data suggested that mild infections were not associated with higher lung cancer rates.
The findings have important implications for medical care. Doctors may need to monitor patients who recover from severe respiratory infections more closely, especially those who already have other risk factors for lung cancer such as smoking history.
Early detection is critical for lung cancer treatment. When the disease is discovered in its early stages, treatments are more likely to succeed and survival rates improve significantly.
The researchers suggest that future medical guidelines may eventually consider severe respiratory infections as a factor when deciding who should receive regular lung cancer screening.
At the same time, the study highlights the broader benefits of vaccination. Vaccines are widely known for preventing severe illness and hospitalization. This research suggests they may also protect against long-term complications such as the immune changes that could increase cancer risk.
While the findings are important, the study also has limitations. The research shows a strong association between severe infection and increased cancer risk, but it does not prove that the infection directly causes cancer in every case. Other factors, such as genetic differences or lifestyle habits, could also influence risk.
Nevertheless, the evidence provides an important warning and a valuable direction for future research. Scientists will need to continue studying how infections reshape the immune system and how those changes may influence diseases years later.
Overall, this study adds to growing evidence that serious infections can have long-term consequences beyond the immediate illness. It suggests that protecting the lungs from severe viral infections through vaccination, early treatment, and prevention strategies may also help reduce the risk of lung cancer in the future.
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