Disease has been a longtime threat to human society, and despite out medical progress it is not just of historic interest. Even aside from any human-engineered bugs that might be used deliberately, natural disease could again (via Real Clear Politics) spread across the planet:
The H5N1 avian flu virus first crossed into human beings in 1997, but it has clearly been mutating in recent years in ways that make it more capable of moving from birds to people. The spate of human infections in mid 2003 in China and Southeast Asia was so serious that more than 100 million domestic birds were killed or died in those countries before it subsided in early 2004, but there was only a few months' respite before bird-to-human transmission began again last June.
The virus has now appeared in wild birds which can carry the virus far beyond its original reservoir in domestic chickens in southern China and Southeast Asia. In late May China closed all its nature parks after 178 migratory geese were found dead from the virus in Qinghai province in the northwest. The most recent outbreak has so far killed 53 people in Vietnam, Thailand and Cambodia. And even more ominously, the first probable case of human-to-human transmission was recorded last September in Vietnam.
The danger of a global flu pandemic that could be as bad as, or worse, than the "Spanish influenza" outbreak of 1918-19 (which killed 40 million to 50 million people, half of them young, healthy adults) comes from the fact that a strain of influenza virus that normally affects only birds can swap genes with a strain that is highly infectious between human beings. If people with the human type of influenza should also be infected with the avian type (through direct contact with infected poultry), the gene swap can easily occur - and direct human-to-human transmission becomes possible.
At that point, given current patterns of international travel, the world might be only weeks away from a global pandemic.
We don't know if avian flu viruses swapping genes with human types caused the lethal Spanish influenza, but that was certainly the source of the much milder "Asian flu" outbreak in 1957-58 (which killed 70,000 people in the United States alone) and the "Hong Kong flu" pandemic in 1968-69 (50,000 U.S. deaths). Given the rate at which influenza viruses mutate, we are overdue for another pandemic - and this one could be a monster.
The H5N1 virus is resistant to most anti-viral drugs, and in the avian form it has been getting steadily stronger. Early outbreaks killed around 10 percent of poultry flocks; more recent ones have been killing up to 90 percent.
In people who have caught avian flu, the death rate has been horrendous: 50 to 75 percent of those infected.
Not only defensive methods such as detection, containment, quarantine, and medication are necessary. We need to get Chinese peasants to stop living with their chickens. A good reason to hope that China does succeed in modernizing (although it needs to become free as well, to avoid beng a military threat).
Another exotic threat is definitely a man-inflicted one but it too could strike at our economy and depending on our vulnerability and capabities of recovering, could kill many of us if our economy breaks down for some period of time. From Winds of Change is this discussion of the threat of an electromagnetic pulse (EMP) weapon:
Unfortunately, such a scenario is not far-fetched. According to a report issued last summer by a blue-ribbon, Congressionally-mandated commission, a single specialized nuclear weapon delivered to an altitude of a few hundred miles over the United States by a ballistic missile would be "capable of causing catastrophe for the nation." The source of such a cataclysm might be considered the ultimate "weapon of mass destruction" (WMD) - yet it is hardly ever mentioned in the litany of dangerous WMDs we face today. It is known as electromagnetic pulse (EMP). [link in article to map added in quote by me]
I do remember this threat discussed during the Cold War but now the spread of technology means that this type of weapon could be within the reach of a lot of other actors.
Redundancy for critical elements of our infrastructure, repair capabilities, and even a limited ballistic missile defense capability will help protect us from or cope with the threat of an EMP attack.
Two exotic threats that we know about. What other attacks are our enemies planning? They want to kill us and as we strengthen defenses in one area they will look to others. That's why the ultimate defense means we have to go after our enemies and kill them and deprive them of more killers. If we ever try to rely on passive defensive measures, we just guarantee that our enemies will think of a way to attack us that we haven't considered.
