As misery spread coast to coast and cubicle to cubicle this flu season, folklore that frigid weather can cause the widespread woe carried as efficiently as the virus itself.
While Palm Beach County’s jump from mild to moderate flu activity coincided with cold snaps brought to South Florida this month by three arctic blasts, frosty temperatures alone do not infect all those without a hat and scarf with fever and chills.
Still, weather’s tie to the flu — and the less terrorizing common cold — is not wholly fairy tale.
Humidity levels, humans huddled in heated homes or air-conditioned offices, and birds flying south for the winter all contribute to the reach of the flu virus, which is widespread in every state except Hawaii and has reached epidemic proportions, according to the Centers for Disease Control and Prevention.
According to the Florida Department of Health, an estimated 2,900 people have died from pneumonia or influenza statewide this flu season. There were also two flu-related pediatric deaths statewide.
The total deaths this year are similar to the same time period the past two flu seasons: 2,988 in 2017, 2,824 in 2016. But is below the more devastating 2015 season when 3,373 people had died statewide of pneumonia or influenza by mid-January.
Palm Beach County is among five counties statewide that have reported five or more flu outbreaks. About 94 percent of outbreaks statewide have been in facilities serving people at a higher risk for the flu, such as nursing homes or daycare facilities. The most at-risk populations are people 65 years of age or older and children.
“The idea about cold weather being connected to catching the flu is an old and imprecise concept,” said Dr. John Lednicky, a research professor at the University of Florida’s College of Public Health and Health Professions. “I try to explain this all the time. There is some truth, and a lot of non-truth.”
Part of what’s true works in favor of sub-tropical South Florida.
To avoid the flu, humidity helps
High humidity can deter the spread of the flu because water in the air encapsulates airborne viruses, making them heavy, and causing them to fall to the ground more quickly. When temperatures are colder, with low humidity, airborne virus particles set adrift by a cough, sneeze, conversation or even breathing can stay mobile much longer, Lednicky said.
Warm temperatures can also cause a virus-carrying mucus droplet to evaporate before making it to its next victim.
“Once the droplet evaporates, it is no longer infectious,” said Mike Farzan, chair professor in the Department of Immunology and Microbiology at Scripps Research Institute in Jupiter.
But when it’s hot and humid, humans go indoors seeking air-conditioning, which removes humidity from the air, creating artificial conditions that are good for spreading the flu.
Florida health officials noted that in the second week of this month, people seeking medical attention for influenza-related illnesses — fever at or above 100 degrees, sore throat and cough — rose sharply and was above levels observed during the previous three seasons at this time.
“Sixty percent of our patient volume has been flu-related,” said Dr. Kyle Petersen, of American Family Care in Loxahatchee Groves. “This is one of the worst flu seasons in recent years.”
Petersen said whether seeking shelter from heat, or cold, people in close quarters also act as effective flu-propagators.
“If you’re up north, and there’s a blizzard, it’s harder to avoid someone who is sick because you’re all brought together,” Petersen said. “A flu virus can live up to a week on a doorknob in colder weather.”
Lednicky said cold temperatures can be more directly tied to catching the flu if someone is outside breathing in cool air, which can irritate or damage the lungs, making them more susceptible to respiratory viruses.
Blame the birds
Birds infected with a strain of the flu migrating south for the winter will bring the virus with them. Lednicky said this is particularly a problem in countries where farming is not operated with bio-security in mind and birds and pigs routinely mix, sharing viruses.
“We try to keep the pigs away from birds and sick humans,” Lednicky said. “That doesn’t happen in the less-funded large swine operations in other countries.”
The idea that cold temperatures alone can cause someone to be sick goes back hundreds of years.
A 2002 paper from Cardiff University in the United Kingdom notes: “The common cold is often said to occur after ‘going outside with damp hair,’ ‘getting one’s feet wet,’ and ‘getting caught in the rain.’”
But the theories have “received no support from laboratory studies.”
Tim O’Connor, spokesman for the Florida Department of Health in Palm Beach County, said South Florida flu activity often peaks between mid-February and mid-March – later than most of the country and coinciding with tourist season.
“The key to all of this, if there is someone who is sick, it’s best not to be around that person, especially in a confined room,” Lednicky said. “If cold weather caused the flu, you would have people in northern climates lying in bed all year because it’s cold and that doesn’t happen.”