Vehicles are emerging as unexpected hotspots for bacterial and viral growth this winter, with frequently touched surfaces inside cars harbouring far more germs than many people assume. A study from Queen Mary University in London found nine times more germs on the average steering wheel than a toilet seat, raising health concerns as respiratory illnesses rise.

Cars as overlooked germ reservoirs

Researchers from Queen Mary University, including microbiologist Dr Ron Cutler, discovered that steering wheels can contain around 700 bacteria per 1.5 square inches, compared to just 80 on a public toilet seat. Dr Cutler said: “While most of the bacteria were unlikely to cause health problems, some cars were found to play host to a number of potentially harmful bacterial species.”

The car boot was identified as even dirtier, with over 1,000 bacteria in the same area. Food residues and litter contribute to the presence of bacillus cereus, which can cause food poisoning from items like rice or pies, and arthrobacter, commonly found in soil or on skin.

Crumbs, condensation and poor ventilation create additional conditions that allow bacteria to thrive, effectively turning vehicles into incubators for winter germs.

Germ transmission heightens in enclosed cabins

Evidence from computational fluid dynamics demonstrates that poor airflow inside cars allows aerosols from coughs or sneezes to linger. This increases the likelihood of viruses such as influenza or SARS-CoV-2 spreading among occupants.

During winter, drivers tend to keep windows closed and use the heating system, which recirculates the same air. Research shows that fully closed windows produce the lowest ventilation rates, with up to 98% of simulated aerosols remaining in the cabin. Opening windows, even partially, significantly increases air exchange, although this is not always practical in harsh weather.

Professionals in the sanitisation industry report that these conditions lead to germs accumulating in seat fabrics and air vents. One provider stated that there has been a significant rise in ozone sanitisation bookings this winter, especially among families and care home drivers.

Growing demand for vehicle sanitisation

This increase reflects heightened awareness following the pandemic. Although 2025 data is still emerging, previous winters saw car-cleaning services report up to 50% rises in deep-clean requests during flu season. Families, in particular, are prioritising vehicle hygiene during school runs and holiday travel, where shared spaces heighten exposure.

Sanitisation specialists emphasise that ozone treatments offer benefits beyond surface cleaning. “Our ozone treatment doesn’t just clean, it also sterilises,” one provider explained. Ozone penetrates deep into upholstery and ventilation systems, neutralising bacteria, viruses and mould spores at a molecular level. It is chemical-free, eco-friendly and suitable for allergy sufferers or those with respiratory sensitivities.

Ozone, a reactive form of oxygen, is recognised for its biocidal properties. Studies confirm it can eliminate over 99% of bacteria, viruses, fungi and moulds by oxidising cell walls and disrupting viral RNA. Treatments lasting 15–60 minutes saturate the cabin and reach areas like air conditioning ducts where moisture promotes microbial growth. Unlike chemical sprays, ozone breaks down into harmless oxygen, leaving no residue and improving air quality for those sensitive to allergens.

Recommended cleaning intervals

Experts suggest different sanitisation frequencies depending on vehicle use. Recommendations include:

• Every three months for everyday drivers.
• Every 6–8 weeks for families with children or pets, or for drivers who regularly carry passengers from other households.
• Monthly treatments for shared-use, taxi or care-home vehicles, especially during flu season.

These intervals draw from health guidelines and detailing-industry practice. Regular sanitisation curbs germ buildup and addresses odours from spills or pets, improving overall cabin freshness. Monthly cycles for high-use vehicles align with observed contamination rates in ventilation systems, where bacteria such as Bacillus licheniformis can thrive.

Customers frequently report that their cars smell fresher and the air feels lighter after treatment, although the greater benefit lies in reduced exposure to harmful microbes.

Reducing risk during winter travel

As families spend more time in their cars during colder months for commuting, school runs and festive travel, routine sanitisation may help limit exposure to seasonal illnesses. Changing cabin air filters every quarter further strengthens protection, with filters capable of removing up to 99% of airborne particles.

Experts stress that while cars can pose manageable risks, maintaining ventilation and cleaning routines helps prevent them from becoming vectors for winter ailments. With flu cases rising across the UK, investment in vehicle hygiene is becoming an important precaution for daily travel.