How Measles Attacks
J Thoendell stashed this in Science
But what is measles exactly? The virus's consequences are about the most uncomfortable-looking thing imaginable—a full-body mat of lesions and blisters—but how does it go about achieving such gruesome effects?
The virus hails from the same family, paramyxoviridae, as deadly viral pneumonia and the since-eradicated rinderpest, an epizootic (animal) disease blamed for the deaths of many millions of cattle and wild animals. Not bad for a molecular structure so simple that it barely qualifies (if it does at all) as being alive in the first place. More so, it's like a tiny machine, a biological landmine packing genetic material instead of explosives.
The measles is transmitted via aerosolized droplets and it doesn't take much. Droplets can hang around in closed environments for up to two hours, but more likely you'd catch it in the usual way of being coughed on or near by someone carrying the virus.
The "secondary attack rate" for people exposed to the virus is upwards of 90 percent. To put that into perspective, the secondary attack rate for the flu is between 10 and 20 percent and around 3 percent for full-blown tuberculosis, while the risk of HIV transmission is roughly around 1 percent per exposure (a rough average of exposure types). Using the r_0 value for measles—how many secondary infections are likely to result from a primary infection—it's about the most infectious thing going with a value of 18. HIV is down at 4 infections per primary and the mumps comes in closest at 10.
(Note however that r_0 values are dynamic, and those are just some recent estimates.)
Basically, the virus finds its way to some healthy cell and chemically binds to it using one of three surface glycoproteins, which are the proteins projecting from cells in order to mediate cell-to-cell interactions. The virus then fuses with its target cell and starts making new genetic material. This becomes the viral mRNA that will go on to "hack" the target cell, which will in turn go on to make more viruses and the process repeats again and again while you start to feel like shit as the infection builds.
With measles (and most viruses you're likely to catch), the dominoes start to fall within lung tissues, where they prey on immune system early-warning defenders:macrophages and dendritic cells. Next, its viral armies move deeper into the immune system, invading lymph nodes and and latching onto white blood cells, who then go on to spread the virus around the body. "The spleen, lymph nodes, liver, thymus, skin, and lungs are eventual destinations for the virus," David Shultz writes for Science.