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Why is the Flu Seasonal?

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ThinkStock

The 2012-2013 flu season is shaping up to be a doozy. The Centers for Disease Control and Prevention have reported that during the first week of 2013, 7.3 percent of all deaths reported through their 122 Cities Mortality Reporting System were due to pneumonia and influenza, crossing their threshold for an "epidemic." Boston has declared a public health emergency, flu cases have tripled over last year in Washington, D.C.El Paso and elsewhere, and a Pennsylvania hospital has had to set up a tent outside their ER to accommodate the crush of flu patients. 

Before the dust and the snot have even settled, the director of the National Institute of Allergy and Infectious Diseases warns that this might be the worst flu season we've seen in a decade. But why is the illness seasonal?

In the temperate regions of the world, the flu tends to strike hardest in the autumn and winter. The conventional wisdom used to be that the influenza viruses either went into a dormant state or persisted at very low levels during the summer months before flaring up again. Scientists have since figured out that, instead of simply lying low during their "off season," the viruses also go globe-trotting, and get transmitted throughout populations all over the world.

In 2007, researchers from Pennsylvania State University and the National Institutes of Health found that the influenza A virus uses its summer travels to meet exotic viruses in tropical areas (which experience year-round flu virus activity), swap genetic information with them, and then roll back into town with enough genetic differences to fool our immune systems. 

Scientists are still working out what exactly triggers the reintroduced viruses to infect people during the fall and winter. The PSU team and scores of other researchers have proposed several explanations, which might work alone, simultaneously but separately, or in combination with each other:

Weather and climate

Influenza viruses do very well in cold winter temperatures and the dry air that goes with them. They can survive longer in dry air than moist air, and hold out longer on exposed surfaces (counters, doorknobs, keyboards, etc.) when they're cold. For humans, dry air means dehydrated mucus and drier nostrils and airways, which could make it easier for the viruses to make themselves at home once they're passed to us. A study on guinea pigs at the Mount Sinai School of Medicine showed that the transmission of influenza is enhanced in cold (41 degrees), dry (20 percent humidity) conditions and declines as temperature and humidity rise (at 86 degrees or 80 percent humidity, it wasn't transmitted at all).

Human behavior

Fall brings a new school year and cooler outside temperatures, and more people spend more time indoors in close contact with each other, giving the viruses an easy route for transmission between hosts. Even in tropical regions that don't have a winter and where flu occurs throughout the year, illness tends to spike during the rainy season when people spend time together indoors.

Human Physiology

Thanks to all that time indoors and the short winter days, our bodies' Vitamin D decreases in the winter. This decrease — or any number of other seasonal tweaks to our immune systems — could leave us more susceptible to the virus for a few months out of the year and act as a "seasonal stimulus" for flu infection. 

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Animals
Watch a Rogue Pet Dog Interrupt a Russian News Anchor on Air
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Last week, a Russian news broadcast briefly went to the dogs after its host was startled by a surprise co-anchor: a friendly black canine that wandered on set, announced its presence with a loud bark, and climbed onto her desk.

 

As TODAY reports, Mir24 TV anchor Ilona Linarte went off script for a few minutes, telling viewers "I've got a dog here. What is this dog doing in the studio?" After the initial shock wore off, she gave her furry guest a tepid welcome, patting its head as she gently pushed it off the desk. ("I actually prefer cats,'' Linarte remarked. "I'm a cat lady.")

Linarte’s query was answered when the TV station announced that the dog had accompanied another show’s guest on set, and somehow got loose. That said, rogue animals have a proud tradition of crashing live news broadcasts around the world, so we’re assuming this won’t be the last time a news anchor is upstaged by an adorable guest star (some of which have better hair than them).

[h/t TODAY]

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Falcon Heavy and Dragon. Image credit: SpaceX via Wikimedia Commons // CC0 1.0
SpaceX Is Sending Two Private Citizens Around the Moon
Falcon Heavy and Dragon. Image credit: SpaceX via Wikimedia Commons // CC0 1.0
Falcon Heavy and Dragon. Image credit: SpaceX via Wikimedia Commons // CC0 1.0

Two members of the public are set to take an historic trip around the Moon, according to an announcement from SpaceX CEO Elon Musk. As The Verge reports, the anonymous private citizens have already placed substantial deposits on the commercial space flight.

The private spacecraft company SpaceX revealed on Monday that the Falcon Heavy rocket will be launching with its Crew Dragon spacecraft in late 2018. The mission will consist of a circumnavigation of the Moon, passing over the body’s surface before traveling farther into space and returning to Earth. In total, the trip will cover 300,000 to 400,000 miles and take a week to complete.

A noteworthy part of the plan is the human cargo that will be on board. Instead of professional astronauts, the craft will carry two paying customers into space. The passengers, who’ve yet to be named, will both need to pass several fitness tests before they're permitted to make the journey. According to The Verge, Musk said the customers are “very serious” and that the cost of the trip is “comparable” to that of a crewed mission to the International Space Station. The goal for SpaceX is to eventually send one or two commercial flights into space each year, which could account for 10 to 20 percent of the company’s earnings.

[h/t The Verge]

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