The Five Diseases You Should Worry About

A primer to the next population-threatening pandemic

Last May, scientists met in Geneva, Switzerland, to update the World Health Organization's plans for pandemic preparedness. It looks like a crisis could arrive sooner rather than later. Thanks to climate change and drug resistance, a handful of deadly organisms are spreading across the globe; some are poised to make a comeback in the U.S. after decades of absence. Growth in international travel and increasing urbanization around the world are sure to make this century's inevitable pandemic much worse, and experts at the Centers for Disease Control and Prevention (CDC) say we're not at all prepared for what's to come. But although bird flu has gotten most of the press (it's still a threat to those in North America, as birds regularly migrate here from areas in Asia where the virus is firmly entrenched), here are five other diseases that deserve your attention.

Malaria

Spread by: Mosquitoes
Kill rate: 0.2%
Death toll: 1 million+ per year As climate change makes parts of the globe warmer and wetter, populations of the disease's host, the Anopheles mosquito, are likely to swell. Malaria kills by destroying blood cells and causing kidney failure. It was eradicated in the U.S. in 1951, but the mosquitoes that carry the parasites are common here, and the CDC warns that it could return at any time. (Malaria-infected mosquitoes are endemic to Central America.) Worse, the parasites are becoming resistant to antimalarial drugs like chloroquine. Resistance has become such a problem that the World Health Organization now supports the use of the controversial insecticide DDT, once widely banned, to control Anopheles populations in Africa.
Graham Murdoch

Smallpox

Spread by: Bioterrorism or clinical accident
Kill rate: 30%
Death toll: 500 million; 2 million per year in the 1960s Well, this one isn't out in the wild. Anymore. Worldwide vaccination programs eradicated smallpox by 1980, but two government-approved labs in the U.S. and Russia keep stores of it. A 2006 investigative report by the British newspaper The Guardian determined that, though very unlikely, it could be made from scratch, or someone could just steal it. Since smallpox is very contagiousa€”it can survive in air for hoursa€”the CDC would consider even one confirmed case a a€œpublic-health emergency.a€ Vaccines exist, but they can cause serious side effects. There is no cure.
Graham Murdoch

West Nile Virus

Spread by: Mosquitoes
Kill rate: 4%
Death toll: 1,086 (U.S. only) No one knows how West Nile virus first got to the U.S. in 1999, but it has since exploded across the country. Last year, 3,630 Americans from 43 states contracted it from mosquitoes, which catch the virus from birds. Less than 1 percent of people end up with severe complications such as meningitis, fatal encephalitis and polio-like paralysis. There is no cure for the infection, though, so stock up on bug spray.
Graham Murdoch

Ebola

Spread by: Body fluids
Kill rate: 50%a€"90%
Death toll: 1,507 Ebola is so deadly that outbreaks have, to this point, quickly burned themselves out; direct contact with infected individuals is required for transmission, and victims generally expire before they can travel far. The virus strips the lining in victims' blood vessels, causing massive internal bleeding. Rarely, cases of Marburg virus, which is related to Ebola, have cropped up outside Africa, the most recent being a fatality in the Netherlands in July. Woe betide humanity if Ebola mutates and becomes transmissible by air.
Graham Murdoch

Dengue Fever

Spread by: Mosquitoes
Kill rate: 0.05%
Death toll: 10,000+ per year The mosquitoes that carry dengue, Aedes aegypti and Aedes albopictus, thrive in warm, wet climates. Last year, the United Nations Intergovernmental Panel on Climate Change announced that by 2085, at least 3.5 billion people will be at risk for the diseasea€”Aedes mosquitoes have recently been found as far north as Chicago. Like malaria, dengue fever (a.k.a. a€œbreakbone fevera€) is a debilitating disease. Of those who develop the more aggressive dengue hemorrhagic fever, 5 percent die, typically from internal bleeding.
Graham Murdoch