February 6, 2015 2:36 pm
Updated: February 11, 2015 2:48 pm

Why is measles so contagious? 5 things you need to know

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WATCH ABOVE: What makes the measles so contagious?

TORONTO – There’s the runny nose, sore throat, red eyes and the trademark rash of red dots. A measles outbreak is slowly growing in Toronto where health officials confirmed a sixth case on Friday.

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The United States is grappling with its own outbreak originating out of Disneyland. Keep in mind, at this same time last year, outbreaks of measles, whooping cough and mumps were widely reported across Canada and in the U.S.

“It’s considered one of the most contagious of the infectious diseases,” according to Dr. Joel Kettner.

READ MORE: Anti-vaccination movement means preventable diseases making a comeback

Kettner is medical director of Winnipeg’s International Centre for Infectious Diseases and a University of Manitoba professor. He was Manitoba’s chief medical officer of health from 1999 to 2012.

Here’s what you need to know about measles and why it’s so contagious.

It has a stealthy “strategy” using your trachea

Viruses are cunning. They’re crafty, they strategize and make tweaks to their attack plan in getting you sick – measles is no exception.

Dr. Roberto Cattaneo, a Mayo Clinic scientist and biology professor, has been studying measles since the 1980s. In that time, he’s learned what sets the measles apart from its peers.

Unlike influenza, which digs its roots deep in your lungs, measles chooses to set up shop higher up in the lining of your respiratory system. And for good reason: it doesn’t want to travel as far up to infect others around you.

READ MORE: 6 vaccination myths debunked

“It chooses to come out really close to the trachea instead of coming out down in the lungs where it’s difficult to be exposed. It gets much more efficiently out of the host,” he explained, calling the windpipe a “trampoline” of sorts for the virus.

Once you cough or sneeze, based on where its positioned itself, it’s ready to launch into your surroundings.

“That’s unique to measles and this is what we discovered,” Cattaneo told Global News.

It’s airborne and it lingers

“You can explain measles’ contagiousness with one word: airborne,” according to Dr. Michael Gardam, chief of infectious disease control and prevention at the University Health Network.

“It is truly an airborne virus which means that somebody with measles is expelling virus when they speak, cough, sneeze,” he explained.

The virus is now in tiny particles that float on air currents and make their way into the next victims’ nose, mouth and throat.

READ MORE: How should health officials reverse an anti-vaxxer movement?

They also linger in the air, on doorknobs, and other surfaces for about two hours, the Centers for Disease and Prevention says.

“If I had measles and was in a room with no ventilation and I left the room, you could bring someone in and the attack rate on that person would be 95 per cent,” Gardam explained.

Scientists say influenza typically spreads from one person to about two or three people. For measles, it’s closer to 20 (if people aren’t vaccinated), Gardam notes.

The experts use the word “spray” often – if someone in the room is sneezing or coughing, the germs spray – and at a pretty far distance, too.

It hinges onto your trachea and lungs, and gets started on replicating.

It hijacks your respiratory system and you’ll feel awful

Once the virus finds an entry point into your body – via your mouth, nose, eyes, for example – it’ll replicate and multiply in the cells of your upper respiratory tract before seeping into your blood stream.

The incubation period could be a week or even 10 days. Then your symptoms turn up: you’ve got a fever, runny nose, sore throat, red eyes, and the signature raised red spots that start on your face and coat your body.

READ MORE: What caused a whooping cough epidemic? Scientists blame parents

“It can be a miserable disease, especially for children,” Kettner explained.

Before your symptoms even begin, you’re still a vector for the disease, too. You could be unknowingly passing it on to the unvaccinated people around you.

If you are vaccinated or you’ve already had the measles, you’re immune. Your body is guarded with the antibodies it needs to tame the virus.

In some cases, it takes a dark turn

The majority of cases don’t end up with complications, according to Kettner. But for a handful, measles can lead to other troubles.

For starters, there’s risk of an ear infection – inflammation in the ear can interfere with drainage in the canal so bacteria can get plugged in there. That could happen in one out of 10 cases, he suggests.

READ MORE: Read Roald Dahl’s call for vaccination after his daughter died of measles

Then there’s pneumonia, which could happen in one to five per cent of cases. Encephalitis, the most serious of the complications, is when the virus gets circulated to the brain causing inflammation of the brain cells.

There could be seizures, loss of hearing or even central nervous system issues. But encephalitis is rare – it happens in about one of 1,000 cases.

But the vaccine is safe – and it works

Your best bet to protect against the measles is to get vaccinated.

“The measles vaccine is one of the best we have,” Gardam says. One shot alone comes with an efficacy rate higher than 90 per cent. A second shot boosts immunity to about 98 or 99 per cent, the experts say.

READ MORE: Toronto Public Health investigating measles outbreak

Right now, the handful of cases in Toronto could be a litmus test for the city to see how well protected its residents are, Kettner says.

“It’s too early to say what the significance is of what these cases will be and if we’ll see more. We can’t conclude if this is going to get much bigger or it’s going to stop,” he said.

carmen.chai@globalnews.ca

© 2015 Shaw Media

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