A new study has found that the virus responsible for the common cold can quietly persist in the human body, even in individuals who show no symptoms.

Researchers from the University of São Paulo in Brazil discovered that the rhinovirus can reside deep within the tonsils and adenoids—tissues located at the back of the throat—effectively using them as reservoirs. The study, based on samples from 293 children undergoing surgical removal of these tissues, revealed that the virus can infect key immune cells and remain there undetected for extended periods.

Unlike its typical behaviour—where it infects the surface lining of the nose and throat, multiplies rapidly, and is cleared by the immune system within a week—the virus was found to penetrate deeper layers of tissue. There, it infects long-lived immune cells such as B lymphocytes and CD4 T cells, allowing it to persist without destroying them.

This hidden presence may help explain why cold outbreaks often occur shortly after schools reopen. Children carrying the virus without symptoms can unknowingly transmit it to others in close, indoor environments, triggering wider infections.

The study further found that nearly half of the children tested carried the virus in at least one site—tonsils, adenoids, or nasal secretions—even though they were symptom-free at the time of surgery. Evidence also suggested that the virus remained active and capable of spreading.

Researchers say these lymphoid tissues may act as a “virus reservoir,” potentially supporting long-term immune memory. However, this persistence could also have downsides. In children with asthma, for instance, lingering viruses may trigger inflammation and worsen symptoms.

The findings also raise concerns about diagnostic accuracy. Detecting rhinovirus in throat swabs may not always indicate an active infection, as the virus could be lingering from a previous illness. This could complicate treatment decisions, particularly in respiratory cases.

Scientists are now exploring whether such dormant viruses could reactivate in patients with weakened immune systems, potentially leading to complications without any new external exposure.

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