Crash Course – Epidemiology

this is how I feel when someone coughs without covering their mouth

this is how I feel when someone coughs without covering their mouth

Alright party people, let’s get right down to it. The Ebola outbreak is on everyone’s mind right now and I felt obligated as your friend and favorite science blogger (let me have my dream) to clear up a few key concepts that get tossed out by the media like candy wrappers. Epidemiologists (scientists who study disease) have their own technical lingo when it comes to disease and GOSH DARNIT I want you to know it too. Hey, look at me…I care.

The terms of the trade…

Agent – the thing that causes the disease, or put another way, the element that is always present with the onset of the disease and whose presence is essential for the disease to occur.

Reservoir – the habitat where the infectious agent lives and thrives. This can be a stagnant, jungle pond or the intestinal tract of a human being

Carrier – person or critter (bat, monkey, bird) that can harbor the infectious agent and is capable of giving it to others. The carrier often lacks any signs or symptoms of having the disease.

Host – Any living thing that can be infected by a disease causing agent under normal conditions. If it’s a brisk November morning and you’re reading “Horton Hears a Who” to a small room of kindergartners on the carpet and half of them have the sniffles, then you are the perfect host for the Rhinovirus (cold). All the conditions are perfect.

Vector – living intermediary between a reservoir and a host. Mosquitoes are classic vectors, especially since they’ll suck blood from a variety of victims. They are equal opportunity pains in the butt.

Transmission – the mode or mechanism by which the disease causing agent is spread (air, water, food, person to person contact, contact with object)

Virulence – refers to the infectious agent’s ability to cause disease. I think of it as a measure of potency. On the other hand, infectivity describes that pathogen’s ability to spread disease to other hosts. When Chicken Pox shows up at a party it doesn’t just stand in the corner by itself. It turns the music up, heads to the center of the floor, and tries to dance with everybody.

Zoonoses – infectious diseases that are transmissible from animals to humans.
It’s funny just how foreign this term is for many of us, since there are so many devastating diseases to the human population (Avian flu, Swine Flu, Black Plague, Rabies, Lyme’s) that we acquire from other species.

Morbidity – is essentially an assessment of just how sick the disease in question makes you. It also has a statistical value representing the relative occurrence of disease in a population.
The definition of morbidity has a wonderfully legal sound to it, but the further a disease moves you away from your normal, healthy physical or mental state the higher the morbidity of that disease is. It is the degree of transformation your body goes through in the course of a disease.

Let’s put it all together…

Gina flew in yesterday from Boston on a late flight back to Georgia. The 5 year old behind her showed her all of his limited edition Shrek action figures on the ride back. One of them was sticky from the gummy worms he’d eaten earlier. She’d gotten back at 10pm but her college peeps were in town and the beers at Karma Mike’s Grill were still half priced until midnight. Work came way too early that next day. She only slept 3 hours and the AC in her office was at full blast.
By noon the sneezes started and her nose would not stop running. Around 2:30 all the name brand, instant coffee in the world could not keep her eyes open to read through all her emails. Later that night her throat felt scratchy and her muscles ached as if she’d lost a cage match. That’s when she remembered the kid on the plane and the suspiciously sticky Shrek. Suddenly Gina understood everything that was happening to her.

Our Cast…

Gina – Host

5 year old – Asymptomatic carrier

Shrek action figure – mode of indirect transmission

Respiratory tract – reservoir of virus

Rhinovirus – infectious agent

I hope this helps. Stay curious, stay classy, and never stop learning my friends 🙂

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