Beth Skwarecki - Outbreak!: 50 Tales of Epidemics that Terrorized the World

One of the oldest diseases known to humankind is still rampant today. Malaria started small, but with the help of mosquitoes, it took over the world.

• Death toll: Unknown; millions
• Caused by: Mosquito-borne Plasmodium parasites
• Noteworthy symptoms: Chills and a fever that recurs every few days
• Fatality rate: Unknown; today the fatality rate is less than 1 percent
• Threat level today: High in many parts of the world.
• Notable fact: About 7 percent of people alive today have at least one gene that helps them resist malaria.

Long, long ago, malaria hit the big time.

You would think this amoeba-like parasite was already doing pretty well, living inside peoples red blood cells and scarfing down their life-giving hemoglobin. But at first it was only doing this in a small neighborhoodprobably the east coast of Africa, around where Ethiopia is today.

But malaria spread. It covered all of Asia before long, including India and China. It expanded into the Mediterranean, and from there through Europe. The eastern coast of England was once known as a place eager to give visitors malarial fevers.

Its hard to pinpoint the date of this spread, especially because many of the people involved didnt know how to writeor if they did, and they wrote about malaria, their writings may not have survived. But once they figured out how to put ink on papyrus or silk, people around the world began writing about malaria: how to diagnose it and what to do once youve figured out somebody has it. The Chinese Huang-Ti Nei Ching (The Canon of Internal Medicine ), the Indian Atharva Veda, and the writings of Hippocrates in Greece all describe fevers that were probably malaria.

Malaria isnt caused by a bacterium or a virus, but by a protozoan. Think of an amoeba, if that helps: a single-celled creature thats related more closely to us than to bacteria, but is still small enough to fit inside one of our cells.

The parasite enters a persons body with a mosquito bite, and rides the bloodstream to the liver to hide until it can make more of itselfamassing an army for its next step, which is a takeover of blood cells.

The liquid part of our blood is clear, and on its own would be unimpressive looking. But its filled with round red cells that keep us alive. With every heartbeat blood goes to the lungs, where the cells are suddenly surrounded in oxygen. That oxygen sticks to the hemoglobin inside the red blood cells, and with the next heartbeat the cells whoosh on their way.

Traveling to the cells destinationmaybe a muscle, or a vital organthe oxygen remains stuck to an iron atom in the center of the hemoglobin proteins. The malaria parasite has its figurative eye on that hemoglobin.