Why don't we quarantine people?

Chris W. - That's an interesting question. We should explain the difference between quarantine, which is rarely done now with humans, and isolation. Occasionally, if someone's got something quite serious that needs not to be transmitted to other people, for example some of the viral or haemorrhagic fevers, we put them in isolation and make sure that nobody can catch what they've got through measures of hand washing and barrier nursing, etc. Quarantine is a broader thing in that you're waiting to see if someone is actually going to develop an illness. So, if say, 10 people are exposed to someone with measles, you could quarantine all of those people by keeping them - although they're well - away from everybody else. But as you can imagine, that can multiply quite quickly and you would have to quarantine an awfully large number of people. In general, we have found that travel restrictions aren't really very helpful in controlling a communicable disease. Horses are a different matter; I wouldn't comment on a veterinary matter, but that's certainly more expensive than a lot of things!

Chris - But the origin of quarantine is interesting, isn't it? Wasn't it the Venetians who came up with this? Originally, they used 20 days and then they went to 40 days. Hence the name "quarantine". This was the time they stopped people getting off ships coming in and they reasoned that if they were going to get something, would get it within that 20 days, or then subsequently 40 days.

Chris W. - And that would cover, as you know, the incubation periods of most common illnesses. That would cover most of the infections that you would be concerned about.