The concept that each person on the planet is just six handshakes removed from every other person has frightening implications

The concept that each person on the planet is just six handshakes removed from every other person has frightening implications when it comes to a highly communicable disease like SARS. Yet the "small world" effect, also known as the "six degrees of separation" phenomenon, may also help explain how severe acute respiratory syndrome has spread so rapidly around the globe, some researchers believe. The disease has infected 8,221 people and killed 735 worldwide, according to the World Health. Physicists, psychologists and mathematicians who study network effects, the scientific field that the six-degrees-of-separation notion has engendered, are busy creating mathematical models that attempt to explain the quick spread of SARS. Mathematicians have long used equations to examine the spread of epidemics, and to help public health officials control them. A recent paper in Science applied these methods to SARS. In the Science article, the researchers assume that most people -- excluding those who come in contact with so-called superspreaders, have about the same chance of developing SARS. Superspreaders, researchers believe, have the ability to infect more people than most patients. Network science, on the other hand, assumes that each person's social habits can increase or lessen his or her chances of getting infected. For example, one might be much more likely to come into contact with someone with SARS by traveling on a plane to Taiwan, a country that has recently seen a high rate of SARS infections.