Scientists See Parallels in Computer, Biological Viruses

Scientists studying how diseases spread believe there are many parallels between computer viruses and biological ones, enough so that when doctors want to know how AIDS engulfed a village in Africa, they may do well to look to their computers.

Contrary to the idea that computer viruses immediately explode into a pandemic, the scientists found that the infection rate starts out very slowly among a small group of friends or a single company.

A computer virus can ``exhibit clique behavior, with pairs of connected individuals sharing many common neighbors, reducing the opportunities for secondary infection events," scientists Alun Lloyd and Robert May write in Thursday's edition of the journal Science. ``As a result, diseases may spread more slowly when contact is mainly local, compared with well-mixed situations."

But after the virus hits that small group, the sky's the limit.

``Within the observed topology of the (Internet), viruses can spread even when infection probabilities are vanishingly small," researchers said. And given the global nature of the Internet, there is ``no threshold for epidemic spread."

While the Internet is practically limitless, there are some sites _ such as Yahoo! and Microsoft's destinations _ that have a lot of customers and employees. If they're infected, they can pass on the bug to many other people.

That's where the prostitutes come in. ``Epidemiologists have long known that if you have transmission that is very heterogeneous, you're much better off ... targeting those individuals with the highest risk,'' Lloyd said in an interview. ``One would target, for example, sex workers. That would be a much better way than targeting people at random."

That knowledge can be translated to computers, he said. ``If you're trying to prevent a computer virus, you want to concentrate on the most highly connected sites."

However, there are some important differences. People who catch the flu get sick, recover, and then may get it again a few months later. Thanks to antivirus software, once an infected computer gets sick, the updated program can block the virus if it comes by again.

The moral? Practice safe surfing.






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