Currently, there is an increase in cases of the H1N1 virus, known as swine flu, in the Delhi-NCR region, and the number of patients seeking hospital care with complaints of cough, fever, and breathing problems has also increased. According to Delhi Health Minister Pankaj Kumar Singh, approximately 3000 cases of influenza have been registered in Delhi this year, of which 2308 are related to H1N1 infection.
It is important to consider this situation in the context of daily car travel. Although the closed cabin of a car may seem protective against the outside world during a commute, dropping children off at school, or being stuck in traffic, it can pose a danger, especially if an infected person is in the vehicle.
According to one study, if the car's air conditioning system continuously circulates air inside the cabin, this closed volume itself can contribute to increasing the level of infection.
Despite the rising number of H1N1 cases in Delhi-NCR, the ICMR clarified that no new strains of H1N1 have been found in India; the existing virus is circulating. Nevertheless, as the number of infected people grows, precautionary measures should not be neglected.
In 2009, during the Influenza A(H1N1) pandemic, a case of infection transmission was recorded in Australia during a car journey. This prompted scientists to study the risk of flu spread in a closed car and ways to minimize this risk.
A study conducted by the National Library of Medicine (NLM) indicates a high probability of increased risk of contracting the flu through air in a car. Within this study, the ventilation systems of two cars from 1989 and 2005 models were tested using the Wells-Riley model to assess the potential risk of infection spread inside a closed cabin.
To understand this study, it is necessary to know what the Wells-Riley model is. This model is a scientific method used to determine the degree of airborne infection spread in a confined space. When applied, it takes into account factors such as the presence of an infected person, the number of infectious particles released during breathing or coughing, the size of the room or car, the air recirculation rate, the duration of the trip, and the number of people.
Simply put, this model shows how much the probability of infection transmission increases when an infected person and other people are in the same enclosed air. In the case of cars, it helps to understand how changing the air conditioning mode and closing windows affects the risk of infection.
The study showed that instead of continuous air recirculation inside the car, the risk of infection is reduced by supplying fresh outdoor air. Specifically, when using the air conditioner in recirculation mode in a new model car, the estimated risk of infection can reach from 59% to 99.9% during a 90-minute trip. This means that a long journey with an infected person in a closed car increases the probability of disease spread.
Infectious particles can enter the air through coughing, sneezing, talking, or normal breathing of the sick person. Since the car cabin is small and closed, these particles can accumulate in the surrounding air. If fresh air does not enter, not only does the number of these particles increase, but the overall risk also rises. The air conditioning recirculation mode exacerbates this problem because it only circulates internal air, reducing the inflow of fresh air.
The risk exists not only in the cabin air but also on surfaces. Virus particles can settle on frequently touched items such as seatbelts, door handles, steering wheels, and infotainment systems after an infected person coughs or sneezes. Subsequent contact with these surfaces and touching the face, nose, or mouth creates a risk of infection. Infotainment systems and interior door handles pose a particular danger.
One of the simplest ways to reduce the risk of infection in a car is to ensure the intake of fresh outdoor air. Slightly opening the windows allows the accumulated infected air to escape and reduces the concentration of particles in the cabin. It is also useful to turn off the recirculation mode of the air conditioner or heater.