Air collected near hospitalized patients with respiratory syncytial virus (RSV) tested positive for the virus far more often than air near patients with influenza A, according to a study in the Journal of Medical Virology summarized by CIDRAP. Researchers in the Netherlands found viral genetic material in at least one air sample for 57% of RSV patients, compared with 15% of flu patients.
The authors caution that a positive air sample does not show that the air could infect anyone. Their test looked for viral genetic material, not live virus, and that limitation shapes how much the finding should change what families do.
The study arrives as the fall respiratory season approaches, and it adds to an unsettled debate about how RSV spreads. For families with infants or older relatives, the more immediate context is that national RSV activity is currently low.
Fifty-Seven Percent Versus 15 Percent in a Small Dutch Sample
The study included hospitalized patients who tested positive for RSV or influenza A on nasal swabs between Dec. 18, 2024, and April 23, 2025. Thirty-nine had influenza, and 21 had RSV.
Researchers collected air samples about 20 inches from the patients' heads. Overall, 18 of the 60 patients, or 30%, had at least one positive sample.
Their summary of the main result was direct. "Air samples were significantly more frequently positive in patients infected with RSV compared to those infected with IAV: 57% versus 15%, respectively," the authors wrote, using IAV as shorthand for influenza A virus.
In raw numbers, that works out to about 12 RSV patients and six flu patients with at least one positive sample. With so few patients, a handful of results could shift the percentages, and all of the data came from one country during a single season.
Viral Genetic Material Is Not the Same as Infectious Virus
The central limitation is one the authors highlight themselves. "The higher air sample detection rate among patients infected with RSV as compared to those infected with IAV suggests that these viruses may have different airborne shedding patterns, although differences in infectious potential remain to be determined," they wrote.
Fragments of viral RNA can be detected even when the virus is damaged or present in amounts too small to cause illness. Showing that air is infectious requires growing live virus in a lab, and the authors acknowledge that their study design does not allow conclusions about differences in infectiousness.
Earlier research has pointed in different directions. A study of six infants hospitalized with RSV in the Netherlands found low levels of RSV genetic material in the air around three of them, only in large droplets, and recovered no infectious virus from the air. The new study's authors note that other research has shown airborne droplets containing RSV can infect human cells in the lab, while some studies have failed to grow virus from positive air samples.
Those mixed results are why the question remains open. The new study does not change CDC guidance, and it does not show that RSV spreads through the air more easily than flu in homes, schools, or offices.
National RSV Activity Is Low for Now
As of Sept. 11, the CDC's respiratory illness data showed RSV and seasonal flu activity at low levels nationally. The overall amount of acute respiratory illness causing people to seek health care was very low. COVID-19 activity was elevated and increasing, although hospitalizations remained low, and rhinovirus/enterovirus and group A strep were increasing.
RSV usually builds in the fall and winter. The CDC considers infants and older adults among the groups most likely to develop severe RSV illness, and hospital wards caring for those patients are the settings where findings like these matter most for infection control.
Local conditions can differ from national trends. Families can use the CDC's community snapshot or check state and local health department updates as the season develops.
Practical Protection as Respiratory Season Approaches
Basic steps still apply regardless of how RSV moves between people. The CDC's prevention guidance includes staying home when sick, practicing good hygiene, and considering a mask when you have symptoms; cleaner indoor air is also part of the agency's advice. Handwashing matters because respiratory viruses, including RSV, can also spread when people touch contaminated hands or surfaces and then touch their eyes, nose, or mouth.
Parents of young infants and adults caring for older relatives can ask a clinician which RSV immunization options apply to their family this season. People with cold symptoms should avoid close contact with babies and frail older adults when possible, including visits to newborns and nursing home residents, until their symptoms improve.
RSV often causes cold-like symptoms such as a runny nose, cough, fever, and decreased appetite. In infants, watch for fast or labored breathing, pauses in breathing, poor feeding, or fewer wet diapers. Those signs, or bluish lips or skin in anyone, need urgent medical care.
This single study does not call for new precautions beyond the CDC's existing advice. Researchers still need to test whether airborne RSV collected near patients is infectious and whether the pattern holds in larger studies across multiple countries. MedicalDaily will follow new data as the respiratory season develops.
Key Questions Answered
What did the study find?
Air near 57% of hospitalized RSV patients contained RSV genetic material in at least one sample, compared with 15% of influenza A patients. The study included 60 patients in the Netherlands.
Does this mean RSV is airborne?
Not necessarily, because the test detected viral genetic material rather than live, infectious virus. The authors said differences in infectious potential remain to be determined.
How large was the study?
It included 21 RSV patients and 39 influenza patients during one season. Larger studies are needed to confirm the pattern.
Is RSV spreading widely right now?
As of Sept. 11, the CDC reported low RSV and flu activity nationally. COVID-19 activity was elevated and increasing, although hospitalizations remained low.
Who is most at risk from RSV?
Infants and older adults are among the groups most likely to become seriously ill. Families with those members can ask a clinician about immunization options.
How can families protect themselves?
Stay home when sick, wash hands often, and consider a mask when you have symptoms. Seek urgent care for breathing trouble, especially in infants.
