No, you don’t “build up your immunity” by getting sick

BTW, you do not “build up your immunity” by getting sick. Neither do your kids; getting sick a lot in daycare as a kid will not make you get sick less often as an adult. You can develop immunity to specific diseases, but there are too many diseases out there and they mutate too rapidly to develop immunity to enough diseases to end up generally less prone to disease.

Getting sick actually makes you more likely to get sick, not less. Take measles:

“A new epidemiological study suggests that [people who’ve had the measles] remain susceptible to other infections for more than 2 years, much longer than researchers anticipated. The results bolster a hypothesis that the measles virus undermines the immune system’s memory—and indicate that the measles vaccine protects against other deadly diseases as well.

Researchers have long known that measles inhibits the immune system, but they generally thought this effect wore off after a few months at the most. However, studies of children in developing countries, where most cases occur, found that measles vaccination reduces the overall death rate from infections for up to 5 years, suggesting that preventing the disease somehow provides protection against other illnesses.” —Mitch Leslie, Science/AAAS News

Not so marvelous now, are they?

Honestly, if getting sick made you less likely to get sick afterwards, everyone who got Smallpox would have had the immune system of doom and never died of anything; malaria would have rendered sub-Saharan Africa a disease-free zone.

Long term, populations get less prone to getting specific diseases just because the most susceptible people have died and people with mutations or behaviors that make them more resistant have survived.

 

I have been reading a lot about AIDS.

Why an African Parasite got named “American Killer”

The humble-but disgusting hookworm’s scientific name is “Necator americanus”–American Killer. (Actually, there are  several hookworm species, but if you live in the US, this is the one to worry aboutt.)

This parasite, like many others, originated in sub-Saharan Africa, where it still infects about 200 million people. East Asia has another 150 million infected.

Each worm lays lays 9,000 to 10,000 eggs per day in your bowels. You helpfully “deposit” these eggs–prior to indoor plumbing, somewhere on the ground. The eggs hatch, and a week later, the baby worms are ready to burrow their way into the foot of any poor sod unlucky enough to step on them.

The babies go into your bloodstream, burrow into your lungs and throat, and then get coughed and swallowed down into your guts, where they make themselves comfortable, drinking your blood and laying more eggs.

Each individual worm only sucks a drop of blood per day, but no one has just one worm; your intestines soon fill with thousands of the bastards.

One of the interesting side effects of horrible infections and diseases is that, given enough exposure, a population will eventually evolve some sort of immunity. Sickle Cell Anemia, while imperfect, is one such adaptation, rendering some folks in malaria-prone regions less susceptible to the disease. People who do not have these adaptations are easy prey for the disease; so Smallpox, vicious murderer of Europeans, tore through native communities like an atomic bomb, killing some 90% of everyone it got near.

So when some idiot had the bright idea to import slaves from Sub-Saharan Africa, not only did millions of humans suffer and die, but Necator americanus jumped the Atlantic and found a new, less resistant host to infect. Poor southern whites, barefoot and often malnourished (un-nixtamalized corn is a culprit here), became unwitting hosts for an organism against which they had no defenses.

No one knew what was going on. The germ theory of disease hadn’t been developed, and no one was autopsying “white trash” kids when they died.

Historian Thomas D. Clark claims, “By modern American Standards of physical, mental, and moral fitness… more than half of the Johnny Rebs who shelled the woods at Shiloh, Chancellorsville, and Gettysburg, or stood with Pemberton at Vicksburg, might have been kept at home. No one can say how much Pellagra and hookworm helped to sustain the union.” (Quoted in “Parasites: Tales of Humanity’s Most Unwelcome Guests,” by Rosemary Drisdelle.)

A later de-worming campaign in the South (after the parasite was discovered) estimated that 40% of children (of both races, I assume) were infected.

The hookworm turned against the Union, though. As Driselle describes, it passed from infected Southerners to Northerners in the horrifying conditions of the POW camps.

At Andersonville, 13,000 people died of starvation, malnutrition, and disease. Driselle estimates that a third were felled by hookworms, but it is hard to imagine that anyone forced to drink Andersonville’s feces-laden stagnant water would have escaped infection.

It was only in the 1880s and 90s that people started putting together the hookworm infection pieces; in the early 1900s, hookworm eradication campaigns started in the American south. (Tips: Wear shoes; Poop in a toilet.) The parasite that had taken down so many Americans was thus formally dubbed the American Killer, Necator americanus, a great anti-disease naming move if I ever saw one, though not quite as great as the bee parasite, Varroa destructor. I mean, do you want something called V. destructor infecting your bees? Obviously not!

(Seriously, who names a disease AIDS? That makes it sound helpful. Should have named it MURDER disease or something like that.)

Hookworm eradication had notable effects on things like health, school performance, and not dying, which is almost always a good thing. (About that time we also figured out that you can’t live on a 100% corn diet for very long.)

 

From time to time, people ungracefully express their dislike of others in terms fear of disease, describing foreigners as “dirty” or otherwise infectious. While such sentiments are crude and insulting, the fact remains that even the most wonderful of strangers may in fact be carrying diseases to which you have no immunity. And with diseases, like devils, better the disease your ancestors might have survived than one they didn’t.