Mediaplanet: What are colds and flu?
Caroline Quach: Colds and flu are respiratory tract infections that are due to a virus and usually begin with a runny nose, cough, sore throat and sometimes fever. Many families of viruses cause symptoms that are very similar, making it very hard to know what is due to influenza (flu) or not. Most people think that feeling as if you were just ‘run over by a bus’ means that you must have influenza. Interestingly, a study of arriving airline travelers showed that those who reported having an influenza-like illness (ILI) (cough OR sore throat AND fever) represented only 11% of the actual cases of influenza detected by nasal swab sampling. On the other hand, in travelers who tested positive for influenza, 99.6% of them had reported an ILI. This means that influenza can present with mild symptoms… that could mimic a normal cold.

"The main objective of viruses is to conquer the world, but they can’t do it without us, because they need to take over our cellular machinery to replicate and thrive."

MP: How do we catch a cold?
CQ: Like all infectious diseases, colds and flu need multiple steps to happen to make you sick. You first need someone with a virus, which then escapes from the sick person, survives in the environment until someone else comes in contact with it, to finally infect a new host. This new host needs to have an immune system either weak enough or naïve enough to allow for the infection to develop.

The main objective of viruses is to conquer the world, but they can’t do it without us, because they need to take over our cellular machinery to replicate and thrive. To do so, viruses need to cause symptoms that are mild enough to allow you to continue going about your daily living – so that you meet other people; the more, the better – and be able to survive in the environment for extended periods of time.

Some research shows that using public transport actually increases your risk of having an acute respiratory infection (ARI) by five-fold, due to crowding and multiple human contacts.

Our research group also showed that, in the elderly – but not in children – going to the emergency department (contact with a lot of other sick people) increased one’s risk of developing an ARI. For young children, daycare represents an even greater risk than going to emergency.
What this really means is that when you have a cold and sneeze or cough – in the bus, going to work, for example; this allows the virus to spread: in the air (1 meter) making people around you exposed to the virus (through droplets) and contaminate your hands. If you decided to leave behind the newspaper you were reading… the next person who picks it and comes in contact with your respiratory secretions (without ever seeing you) may contaminate their hands (most viruses survive for hours on surfaces).

No one catches a cold directly through hands. However, we have a tendency to rub our face, nose and eyes… and get infected. Most viruses change often (to escape our immune system) and our immune system tends to become forgetful – even more so as we get older. So the very young and the very old are more at risk of developing an infection.

"Being vaccinated yearly against influenza is another way to protect ourselves."

MP: Can we prevent infections?
CQ: The most effective and basic measure is hand hygiene. This does not mean that we all need to carry around hand sanitizers to wash our hands constantly – but rather that we should wash our hands when appropriate, mainly after contact with highly touched surfaces – and keep our hands away from our face. Crowded spaces are, of course, a risk factor. However, most of us cannot avoid them.
Being vaccinated yearly against influenza is another way to protect ourselves against influenza only, not against any of the other viruses. We know that influenza vaccines are not 100% efficacious. Their effectiveness depends on the match between the strains in the vaccine that year and what is actually circulating.

It also depends on our immune system: the weaker it is, the lower the response to the vaccine and the lower the protection. Yet, for people at increased risk of influenza complications and those in close contact with them, it is better to have a 50% chance of being protected through vaccination than a 0% chance without vaccination.

MP: What about a healthy lifestyle?
CQ: One hundred and fifty-four adults were randomized to meditation, exercise or placebo6 to see if meditation would decrease the risk of acute respiratory infections (ARI). The meditation group, compared to the control group had fewer illness days and a lower global severity score. The exercise group, compared with the control group had fewer illness days but the global severity was similar. Adjusting for covariates, both total days of illness and global severity appeared to be lower for meditation, but not for exercise. This seems to show that less stress leads to fewer ARIs.
Sleep (quantity and quality) was also shown as important. Those sleeping less than 7 hours had almost a 3-fold increase in their risk of developing cold symptoms after being challenged with rhinovirus, compared to those who slept 8 hours or more per night. People who had less than 92% sleep efficiency had a 5-fold increase in their risk of developing a cold compared to those with 98% sleep efficiency or higher.
Finally, 105 young adults 18 to 30 years of age were randomized to 3 times per week sunbed exposure in the middle of the winter for 8 weeks vs. daily vitamin D (1000 UI per day) supplementation or to no intervention. The study results showed no real difference between groups.
All in all, colds and flu are and will be part of our winters, but there are ways to remain healthy: listen to what our mothers told us, get your annual flu shot (if recommended for you) and, most importantly, wash your hands!