“Infectious agents — whether viruses or microbes — are constantly testing their environment for new host species to survive.” Beatrice Hahn, University of Alabama
Tiny organisms that can make us sick, known as microbes, are magicians at both changing and exchanging ways to survive in animal (and human) bodies. We have get new flu shots each year because H. influenzae, the flu virus, is constantly mutating. Salmonella enteriditis bacteria, which can infect eggs have received “injections” of genetic information from other bacterial species, which makes them more toxic to humans. Bacteria mutate often and trade antibiotic resistance like kids trade Pokemon cards.
One trick that makes microbes especially dangerous to us is their ability to occasionally jump from animal to animal, or animal to human. Our immune systems can often fight off infections that have been circulating through the human population over time, because we “recognize” the microbes trying to infect us. However, when a microbe jumps from animal to human, our bodies often don’t have the ability to recognize it or fight it off. (Researchers speculate that the 1918 Flu virus that killed over 40 million people may have been passed from birds to pigs, and then to humans.)
It is often even easier for a microbe to jump to a closely related species, like from chimpanzee to human, since we are so similar. To illustrate this idea, imagine a bacteria that usually infects circles. Chances are, it would be more likely to recognize and infect an oval than to infect a square. For a microbe to go from a chimpanzee to a human would be like going from circle to oval, while a jump from bird to human would be more like jumping from circle to square.
In the news this week, I learned that researchers have been racing to be the first to discover which of our primate relatives passed the parasite Plasmodium falciparum, which causes malaria, to the human population. This race comes on the heels of a paper showing that H.I.V. probably originated in monkeys over 32,000 years ago before being passed to chimpanzees, and then on to humans. A scientist named Beatrice Hahn, from the University of Alabama, along with many collaborators, won the race and demonstrated that the malaria parasite jumped from western gorillas to humans in a single leap, probably between 5,000 and 300,000 years ago.
We don’t worry much about malaria in the United States, but P. falciparum is a killer. According to the World Health Organization, or WHO ,”In 2008, there were 247 million cases of malaria and nearly one million deaths – mostly among children living in Africa. In Africa a child dies every 45 seconds of Malaria, the disease accounts for 20% of all childhood deaths.” If malaria has been around for over 5,000 years, we can only imaging how many people it has killed.
Hopefully, these findings will allow researchers to compare the original parasite, found in gorillas, to the modified one, found in humans and discover new avenues for preventing and curing the disease it causes. Maybe researchers will also gain more insight into how microbes jump from one animal to another, allowing us to prevent, or quickly halt diseases like malaria, H.I.V., or the 1928 flu before they become pandemics and kill millions of people.