Two respiratory viruses that most people have never tracked are currently elevated across the country, while influenza and RSV remain at low levels. The Centers for Disease Control and Prevention lists parainfluenza virus and respiratory adenoviruses as elevated nationally in its most recent surveillance update.
The agency pairs that with a qualifier that belongs in the same breath. CDC states that its data show these trends are expected for this time of year.
That combination is the actual story, and it runs counter to the instinct a headline about elevated viruses usually triggers. Something being elevated and something being alarming are different claims. For a household, the useful takeaway is not that a new threat has appeared but that a summer cough in August has more plausible explanations than most people assume, and that a negative flu or COVID test does mean nothing is there.
The Viruses Filling a Quiet Summer
Parainfluenza and adenovirus are common, longstanding respiratory viruses. CDC notes on its respiratory illness surveillance page that they cause symptoms familiar from other respiratory infections, including cough, fever, nasal congestion, and shortness of breath, and that severe infection may progress to bronchitis or pneumonia.
There are four types of human parainfluenza virus. The clinical overview of parainfluenza viruses explains that types 1 and 2 are most often associated with croup, the barking cough and noisy breathing that send parents to urgent care at night, while type 3 is more often linked to bronchiolitis, bronchitis, and pneumonia and usually peaks in spring and early summer. Adenoviruses are broader still, causing cold- or flu-like illness, conjunctivitis, and gastrointestinal symptoms depending on the type, and the adenovirus information page notes that they circulate year-round rather than in a defined season.
CDC states there are no vaccines available for either illness, a meaningful difference from influenza, COVID, and RSV. Prevention is the unglamorous set: handwashing, cleaning surfaces, and staying home while symptomatic.
The seasonal context matters for interpreting any of this. According to CDC's data channel summary, the overall amount of acute respiratory illness driving people to seek care is very low, influenza activity is low, and RSV activity is very low in most areas. COVID activity is low in many regions but increasing in the West and South. When the dominant winter viruses recede, the viruses that were always circulating become the visible ones.
Separating an Elevated Trend from an Emerging Threat
This is the part that protects readers from a misread.
Elevated in CDC surveillance language means activity above the baseline for the measure being tracked, based on emergency department visits and laboratory test positivity. It does not, on its own, describe severity, nor does it indicate a new or changed virus. CDC's explicit statement that the trend is expected seasonally rules out the interpretation that would otherwise be natural.
There is a second reason to be cautious about reading too much into surveillance numbers, in either direction. Testing patterns shape them. Many people with a summer cough are never tested for parainfluenza or adenovirus at all, because a specific result rarely changes treatment for an otherwise healthy adult. Surveillance captures the people who sought care and were tested, not everyone who was infected.
CDC's same update addresses a bacterial infection in the same frame. Whooping cough continues to circulate, the agency says, at lower levels compared with post-pandemic peaks. Federal pertussis surveillance shows fewer cases reported in 2026 than at the same point in 2025, with the last peak in reported cases occurring in November 2024. Those counts are preliminary and are revised as states report.
Pertussis is worth separating from the viral trends for one reason. Unlike parainfluenza and adenovirus, it is vaccine-preventable, and the vaccine that protects newborns is given to the pregnant parent. Infants under one year face the highest risk of severe disease, and the recommended dose during pregnancy passes antibodies to the baby before the infant's own series begins. MedicalDaily reported earlier this summer that pertussis was still circulating while other respiratory illnesses stayed low, and the trend since has been downward rather than upward.
Mycoplasma pneumoniae, another bacterial cause of chest colds and pneumonia that has drawn attention in recent years, is currently low across most of the country.
The People for Whom a Common Virus Is Not Minor
Risk here is not evenly distributed, and saying so is more useful than a general warning.
Parainfluenza viruses commonly infect infants and young children, and the CDC notes that in children they can cause croup, bronchitis, bronchiolitis, and pneumonia. Croup that causes stridor at rest, meaning the harsh, noisy breathing continues while the child is calm, warrants urgent evaluation rather than a wait-and-see approach. So does any labored breathing, chest retractions, bluish color around the lips, or a child who cannot drink.
In older adults and people with weakened immune systems, parainfluenza can lead to bronchitis and pneumonia. For adenovirus, the CDC identifies people with weakened immune systems and those with existing respiratory or cardiac disease as facing the highest risk of severe illness, a group that includes transplant recipients.
For an otherwise healthy adult or older child, the guidance is ordinary. Rest, fluids, and time. Contact a clinician for fever lasting more than a few days, symptoms that improve and then worsen, chest pain, or shortness of breath. Seek urgent care for difficulty breathing, confusion, or bluish lips.
There is also a practical point about testing. A person with respiratory symptoms who tests negative for COVID and influenza has not been told they are not contagious. Parainfluenza and adenovirus spread the same way, and the same courtesy applies, particularly around newborns, older relatives, and anyone receiving cancer treatment.
CDC reviews this list weekly and updates it when trends change. The agency's respiratory surveillance will shift attention toward influenza, COVID, and RSV as fall approaches, and the practical decision most households will face in the next two months is a vaccination one for those three. MedicalDaily will report changes in the surveillance picture as the fall season begins.
Key Questions Answered
What is elevated right now? CDC lists parainfluenza virus and respiratory adenoviruses as elevated nationally, while influenza is low and RSV is very low in most areas.
Is that a cause for alarm? The CDC states that these trends are expected for this time of year. Elevated describes activity above a baseline, not severity or a new threat.
What symptoms do these viruses cause? Cough, fever, nasal congestion, and shortness of breath. Severe infection can progress to bronchitis or pneumonia. Parainfluenza types 1 and 2 are the usual cause of croup in young children.
Is there a vaccine? CDC says no vaccines are available for these illnesses. Prevention relies on handwashing, surface cleaning, and staying home when sick.
Who is most at risk? Infants and young children, older adults, and people with weakened immune systems or existing respiratory or cardiac disease, including transplant recipients.
When should a parent seek urgent care? For noisy, harsh breathing that persists while the child is at rest, labored breathing, chest retractions, bluish lips, or inability to drink.
What about whooping cough? CDC says it continues to circulate but at lower levels than post-pandemic peaks, with fewer cases reported in 2026 than at the same point in 2025.
