Most of us associate colds and flu with colder weather. But that doesn’t mean we can’t get cold during the summer. Some viruses are even more common in summer than in winter. So why do we get cold in the summer?
Influenza virus and respiratory syncytial virus (RSV) are more common in the winter months because cooler temperatures and longer periods of time spent indoors around other people provide favorable conditions for them to spread.
But in the summer, enteroviruses and parainfluenza virus 3 are much more common, and infections with these viruses tend to peak in the summer and early fall when the weather is warmer and more humid.
Both viruses cause typical cold symptoms, including runny nose, low energy, muscle aches, cough, headache and sore throat. Parainfluenza can sometimes cause bronchitis and pneumonia in people who have a poorly functioning immune system.
While these symptoms are similar to allergies, the telling difference is that allergies tend not to cause fever or body aches and rarely cause a cough. Colds last from a few days to two weeks, but depending on what triggered the allergy, allergy symptoms can last all summer for some people, he explains Medical Xpress.
Why do we get cold in summer?
So why do we get cold in the summer? It seems counterintuitive that certain viral infections are more common in the warmer months when we spend more time outdoors. But in the warmer months, we socialize and travel more, which means we get to be around more people, sometimes from different parts of the world. Many of us also gravitate towards air-conditioned indoor environments when the weather is warm.
But the structure of viruses can also explain why some spread more easily in the warmer months and why we get colds in the summer.
For a virus to spread and infect healthy cells, it must survive both outside and inside the human body, and it must also use the cells’ tools (such as DNA) to multiply.
Encapsulated viruses
Viruses are surrounded by a protein “shell”, called a capsid, which not only gives the virus its shape, but also protects the genetic material inside. The capsid also helps the virus attach to human cells to cause infection.
Some viruses (called “enveloped viruses”) are additionally surrounded by a lipid (fatty acid) coat. This viral coat helps the virus avoid destruction by the immune system. It also has a role in interacting with human cells to cause infection.
Many “winter” viruses (including influenza and RSV) are enveloped viruses. Encapsulated viruses tend to be more vulnerable to heat and dryness than those lacking the capsule. This is one of the reasons why these winter cold viruses are thought to survive best in colder environments.
Summer cold viruses
While some summer cold viruses (such as enteroviruses) do not have a capsule, others (parainfluenza virus 3) do. In fact, parainfluenza virus 3 is more common when temperatures are high and humidity is low (although it can survive in a range of different humidities).
This suggests that other parts of a virus’s structure besides the capsule may influence the conditions under which it can best survive and spread, but more research will be needed to better understand this.
The interaction between temperature and the immune response to a virus may also play a role. One study found that mice exposed to temperatures of 36°C had a diminished immune response against the influenza virus. However, more research is needed to confirm this finding in humans.
Why are we getting cold in summer, especially in 2022?
Many people have reported suffering from summer colds this year, leaving many to wonder why and if the pandemic played a role. So, after explaining why we get cold in the summer in general, researchers also focused on this detail.
Immunity to common cold viruses is short-lived. So every season, when we are exposed to new variants, our immune system has to adapt. But during the pandemic, various containment measures, such as social distancing and wearing masks, limited the exposure many people would normally have to such viruses.
When we were able to go out again after isolation, cold viruses started to circulate, but our immunity had not been strengthened by exposure to that virus in the previous year.
While the predictability of seasonal viruses has changed since the emergence of COVID-19, the increase in summer colds seen this year is likely due to people traveling more, returning to crowded spaces, wearing masks less often and not distancing themselves as much for a long time, but also because of the lack of usual exposure to respiratory viruses in the previous year.
Heat
This year, many parts of the world have also seen extremely high temperatures and a series of heatwaves. These fluctuations in temperature and humidity may have played a role in the transmission of common cold viruses this year.
These factors will become even more relevant in the future and could even change the time of year we see certain viruses. Climate change could make the spread of viruses even worse in the future.
Since there is no vaccine for the summer cold, the best thing you can do to avoid it is to stay away from people who are sick (if possible), wash your hands, and avoid touching your face.
Why do we get cold in summer and how can we get over it?
If you are unlucky enough to get the virus, the advice for getting over a cold is the same as for a winter cold: drink plenty of fluids, get plenty of rest and eat nutritious food. To protect others, it is also recommended to cough or sneeze into your elbow or tissues.
It might also be worth thinking about how you can protect yourself from getting sick as temperatures cool over the coming months. The flu shot is recommended every winter for certain people, so it’s wise to check if you’re getting a flu shot this year.
The flu has been particularly bad for Australia this year, and forecasts suggest it will be the same in many parts of the world this winter.