The Reason So Many Of Us Get Sick In Spring

21/10/2015 6:49 PM AEDT | Updated 15/07/2016 12:50 PM AEST
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The sun is shining, temperatures are rising and you're balled up in bed with a fist full of tissues. While getting the flu in spring seems like a sick joke (pun intended), there's sound reason why it occurs.

The culprit? Air conditioning.

“The flu virus responds to humidity -- the virus does not like humidity. If you're in a building that is air conditioned and relative humidity is low (under 30 percent), or on an airplane where relative humidity is as low as 12 percent, you're in an environment flu can easily spread,” Dr Mary-Louise McLaws, Professor of Epidemiology in Healthcare Infection and Infectious Diseases Control told The Huffington Post Australia.

"That's why the flu seems to be able to spread so effectively at work or on an airplane."

This makes perfect sense if your workplace has cranked up the chill factor to counteract the newfound warmth outside, or if you're fond of a chilly household.

“While humidity levels can not be increased on airplanes, it can be done in office buildings. Often the maintenance team can adjust the humidity in the air conditioning so that it's at least higher than 20 percent. At times it might be mildly uncomfortable for men who wear suits on very hot days, but it will certainly reduce the increased likelihood of getting the flu,” said McLaws.

Frustratingly, there's not much you can do to protect from spreading the flu because we don't know were about to get sick at the time we are contagious.

“Strangely enough, the flu is not as communicable as we might think. You are highly infectious during the incubation period which is about 24 hours -- meaning you are only contagious 24 hours before you get initial symptoms of chills, and coughing and watery eyes. So it's very hard to put infection control procedures in place that will reduce the likelihood of passing it on simply because you don't realise you're getting sick at the time,” said McLaws.

“We know that flu spreads mostly on tidal breath -- that is speaking -- and will travel for over a metre in the right relative humidity. Outdoors, when you factor in UV rays, wind and humidity it doesn't have long enough to hang in the air to spread, but in an office where doors aren't open and closing frequently and if the relative humidity is very low then it can stay in the air for up to five or 10 minutes.”

So, what can we do (aside from relocating to the Bahamas)?

“The best option is a vaccination. We know that vaccinations aren't perfect as it doesn't work with a very small proportion of the community, and we also know we need to get a new vaccine mostly every year," said McLaws.

"But given that we don't know when we are contagious, prevention is still the best approach. Vaccine now covers both the A and B strains. Once it only covered A but now covers both, so it's worth getting.

"A flu shot covers you for that type of flu for the season, or a little longer. People who have been vaccinated think they don't get the flu but they may do and not realise. You may feel exhausted, tired, run down; that's the flu going undiagnosed as you're experiencing a very mild bout due to the protection for the vaccine."

Beyond getting a shot each year, you might think that regular hand washing will help -- and that's true -- but only to a degree.

“Hand hygiene is important, but on average we touch our face 20 times an hour and about a quarter of that is touching the mucus membranes -- so every time you put your hand to your mouth or your nose, you need to use an alcohol based hand rub. So while good hand hygiene is a fine idea in theory, it's hard to execute," said McLaws.

"Certainly you should be washing your hands before preparing food and after you've touched your mouth or nose while you're sick, but even then it’s only going to have a small impact because sadly you don't realise you're viremic in the lead up to becoming obviously sick."

Lastly, ever wondered if you need to turf every item you've come in contact with? Don't worry too much.

"There is no need to throw away your toothbrush and water bottle once you're better. The germs won't live very long, plus you've already had the flu so you're not going to get it again because your antibody levels are high and protective against getting another bout of that strain. Wash your water bottle every few days -- you should be doing that anyway so that it doesn't build up mould which can make you unwell,” said McLaws.

“If a close loved one was going to catch your flu they would have had symptoms a day or two after you.”

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