I can see the mistake where people think acute means little or small or minor, probably because in the back of their head, they're remembering that an acute angle is one which is less than 90 degrees. And because they hear acute versus chronic, they correctly assume that chronic is the opposite, and so therefore, it must mean severe or strong.
I say 'correctly assume' because chronic is, indeed, the opposite of acute, but only in definition. And, as they have the incorrect difinition of acute, they also have the incorrect definition of chronic.
Medically, acute mean sudden or brief, while chronic means long lasting.
An acute injury would be one suffered, for example, in a car accident, no matter how severe. Getting an arm or leg amputated in that car accident is still an acute injury.
The months-long pain suffered because of that injury can be chronic. That is to say, the pain can last for several months, or even years.
Chronic back pain, even if very minor, is back pain which has lasted for quite some time, even several years. It can stay very minor, or get progressively worse, but it is chronic.
The reason I bring this up is because of SARS. It means Severe Acute Respiratory Syndrome. The virus of SARS affects the body at a very high rate of speed. The virus' incubation period is very short compared to most viri, and will have you sick a lot faster than most other virus infections. In fact, I've heard that it can cause a full-blown pneumonia within a day. This would be considered acute. It is severe because of just how bad it can get.
If this one-day incubation period is correct, you can be infected one day, and lying in the hospital the next day, dying. If you are relatively healthy, and you have a strong immune system, chances are that it will take longer. I think that this rate of decay in your system only applies if if your immune system is weak, either from constantly fighting other illnesses, or if you have immunosuppressive diseases such as AIDS/HIV. But even with a healthy immune system, it can still show its effects within a matter of a few short days.
As I posted in my community, health_fitness, and in the message just before this one, no one in the United States has yet died from SARS. At least, not according to my latest information, which is now about 24 hours old. I have not had a chance to check up on updates to any figures.