As the temperature continues to plunge this winter, many Canadians will turn to scarves -- and more recently necktubes -- to keep their necks and faces warm. These swatches of fabric ensure those areas left open by jackets and coats are kept safe from the prevailing winds and wayward flakes of snow. Yet, they may serve another purpose as protectors of our health.
It is common knowledge winter is prime time for the spread of respiratory viruses, such as the cold and flu. But other pathogens are also common this time of year, including pneumonia, pertussis, and measles. Despite the different nature of these organisms and the diseases they cause, one common trait exists. They all tend to spread in the air.
Over the last few years, most of the attention to the spread of pathogens has focused on hands. It's because most infections do arise from the inadvertent transfer of microbes from the hands to the nose and mouth. However, the airborne route of infection still remains a significant factor in the spread of infectious disease. But exactly what risk the air poses has been relatively unknown.
Now we may have a better understanding thanks to an international group of researchers who have taken on the task of properly explaining how pathogens behave in the air. Their analysis of aerosols and droplets has provided a good reason for having that scarf or necktube.
The goal of the research was to calculate a reliable model for the spread of infectious agents through the air. They accomplished this by examining a wide spectrum of daily life. They incorporated aspects such as individual health, community activities, national trends, and even global climate. If they were successful, they would be able to predict the potential for infection spread anywhere in the world.
The model was based on the well-known natural mechanism of dilution. Much like when salt is dissolved in water, the researchers knew viruses and bacteria decreased in concentration after being expelled by a sick person. The team wanted to find the factors involved in this dilution so they could calculate a particular risk to another individual.
The first level of analysis involved the sick individual, also called the donor, and the amount of bacteria or virus sent into the air. Depending on the type of infection, and the stage of illness, the concentration varied. An individual could either mildly pollute the surrounding environment -- such as skin shedding -- or could render the entire area toxic thanks to a cough or sneeze.
For anyone within a reasonable distance of two metres or less, the risk for exposure was relatively high. However, this distance could be extended depending on the environment. For example, the presence of wind, whether natural or ventilation, could maintain the risk at greater distances. This addition of complexity meant any analysis of risk required an understanding of the climactic factors due to both weather and interior climate control.
The next stage of analysis involved the individual at risk, known as the recipient. A number of factors were considered including the size of the airborne particle and the tenacity of the pathogen once entered into the body. While these did play a role, perhaps the most important factor tested was the state of the person's immune system. Normal, healthy people would naturally be able to fight the infection in comparison to those with compromised immunity.
The final factor analyzed was the environment although the authors explored a much wider spectrum than simply those few feet between individuals. They examined the effects of air pollution, urbanization, socio-economic impact, and weather. While the authors did admit these factors were remote in comparison to the donor and recipient, they did have an influence on model.
When the results were complete, a complex model was developed in which all factors played a role in the airborne spread of pathogens. For the researchers, this exercise enabled them to identify many gaps in knowledge for future research. However, for those wishing to learn how infections transfer in the air, the only acceptable answer based on this model would be: it's complicated.
As for those wanting to stay safe based on the results of this model, there are two options. People can determine the concentration of the pathogen upon expulsion, the genetic makeup of the bacterium or virus, analyze the humidity, temperature, and wind speed velocity of the area, and assess their own immune function. Or, they can simply block the invader from gaining access to the body by using a mask.
While in healthcare, the mask may be the best option, for the majority of Canadians this type of protection is simply not feasible or fashionable. Thankfully, those scarves and necktubes can provide enough protection to ensure you don't get exposed to any great extent. Granted, they may not be as efficient as a mask but they can definitely reduce the risk so you can enjoy winter with less worry.
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