Amid the surge of seasonal illnesses such as influenza, colds, RSV, norovirus, and COVID-19, UK health experts are highlighting adenovirus, a common but often overlooked pathogen. Frequently mistaken for generic respiratory infections, adenovirus is contributing to the current wave of sickness, sometimes described as a “mystery virus” or fast-spreading throat bug. Unlike flu, which peaks in colder months, adenovirus circulates year-round and can reinfect individuals multiple times throughout life.

The NHS estimates most people will experience at least one adenovirus infection by age ten. Ian Budd, Lead Prescribing Pharmacist at Chemist4U, notes that many infected individuals assume they are simply “under the weather.” Adenovirus symptoms can include fever, pink eye, cold-like signs, bronchitis, pneumonia, ear infections, gastrointestinal upset, or croup in children. While generally milder than influenza, the virus has no vaccine, and its simultaneous circulation with other respiratory viruses has led to increased GP visits.

Children, especially around five years old, are most affected, but anyone can contract the virus. Adenoviruses comprise dozens of strains, with some targeting the respiratory system and others affecting the eyes or gut. The virus spreads easily in communal settings such as schools, nurseries, hospitals, and care homes. It can survive on surfaces for extended periods, meaning direct contact is not always necessary for transmission, and infected individuals may continue shedding the virus even after recovery.

Treatment is supportive, as antibiotics are ineffective. Rest, hydration, and fever management with paracetamol are recommended, along with humidifiers or saline drops for congestion. Severe cases—particularly in infants, older adults, or immunocompromised individuals—may require hospital care. Recovery typically lasts from a few days up to two weeks.

Budd explains that adenovirus spreads more during winter and early spring when people are indoors. Reduced exposure to common viruses during COVID-19 may have lowered immunity, increasing susceptibility. To prevent transmission, the NHS advises prioritizing hygiene, including regular handwashing and cleaning of shared surfaces and objects. Adenovirus is not new but is now appearing more prominently alongside other seasonal illnesses.