The season for colds is so predictable that virologists can practically circle its start date on a calendar. The first big spike starts "about two weeks after students go back to school in September,” says Dr. Ellen Foxman, an assistant professor of laboratory medicine at Yale School of Medicine. It rears its ugly head again as winter moves into spring; runny noses and sore throats ensue.
For much of the summer, though, rates of cold and flu bottom out—in part because the temperature of the air in and around your nose is so warm. “To get sick from rhinovirus, you have to get the virus in your nose, and then it has to grow enough to actually make you sick," Foxman explains. “We found that your body fights that infection more effectively and blocks it from growing if the cells that are infected in the nose are warm.” A drop in temperature of just four degrees Celsius can cause a 1,000-fold increase in the growth of a virus, she says.
So why, when people are unlucky enough to catch them, do summer colds feel so miserable?
It's not that they're actually more severe. Some viruses, called enteroviruses, are more likely to cause colds during the summer than at other times of the year, but while this type of virus can cause some nasty symptoms, that’s not true across the board, Foxman says. Also, rhinoviruses are still the most common kind of cold during the summer months, and their symptoms don’t vary from season to season.
Instead, the reason why summer colds are so insufferable may be more psychological. “My view is that severity [of a summer cold] is perceived as worse than a winter cold because summer colds are not so common,” says Dr. Ronald Eccles, professor emeritus and former director of the Common Cold Centre at Cardiff University in the UK. The seeming injustice of catching a cold when it's not even cold season—and the fact that every person you know feels fine and dandy—makes your symptoms feel extra crummy, he says.
Some research supports this theory. A recent study published in the journal Health Psychology found that feeling lonely can make a person’s cold symptoms feel worse. “There’s a lot of work showing that when people are lonely and experiencing any physical stressor—whether it’s pain or illness—they perceive that stress as being of higher intensity,” says Chris Fagundes, the study’s coauthor and an assistant professor of health psychology at Rice University. “Our finding was that lonelier people feel worse when they are sick than less lonely people.”
Feeling left out or isolated—like you would when you're stuck in bed while all of your friends are having fun in the sun, for example—can promote feelings of loneliness. “It makes sense that if you think everyone you know is at the beach or outside doing enjoyable things and you’re stuck in your room for a week, that could heighten perceptions of loneliness and perception of cold symptom severity,” Fagundes says. More of his research links feelings of social isolation to a heightened inflammatory response. This could also explain why, when you’re feeling singled out by summer illness, your symptoms may feel more extreme.
If a summer cold pays you a visit, phone a friend. Doing something social—even if it's not as fun as drinking margaritas on a roof deck—may help relieve some of your suffering.