Gene Whitley, age 9, of Shreveport, Louisiana, for his question:

What causes a fever?

You may feel boiling hot on a summer day. But if a fever thermometer says that your body temperature is normal, then you are not sick with a fever. But when the body is attacked by germs or gets a case of sunstroke, its temperature may rise above normal. Then you have a fever.

Sometimes a doctor can tell when you are coming down with a fever. You feel droopy and dopey. Your skin feels goose pimply chilly and your pulse is a bit faster than it should be. Then comes the next stage. Your body feels hot and dry. Your skin is flushed with blushes and you are oh so thirsty. Your heart beats faster and the thermometer shows that your temperature is higher than its healthy 98.6 degrees. When this restless, uncomfortable stage is over, you feel well enough to take a long, calm sleep. Your skin becomes moist, your breathing slows down and your feverish temperature falls back to normal.

This feverish chain of events tells the doctor that your body is at war. It is fighting an attack from enemy germs with all its might. The fever is part of the battle that goes on inside without any orders from your head. The body expects these attacks of sickness. It keeps many weapons on hand to defend itself and sometimes it creates special weapons to deal with a new kind of enemy. Some of the soldiers are tiny white cells that float around in the circulating stream of blood.

When you have a fever, zillions of white cells called phagocytes have been extra busy. A tiny phagocyte seeks out an enemy bacterium germ. When it captures the enemy, it wraps its6lf around it. The captured germ can do no more harm to the body. But the arresting officer sends out a message; it gives off a special message carrying chemical. And this chemical causes the body to push up the thermostat that usually keeps it at a comfortably normal level.

As the body's central heating system gets hotter, the patient goes down with a fever.

When the enemy invaders are defeated, the work of the arresting phagocytes is done. Still carrying their germs, they seep into the liquids of the body and make their way outside along with the usual waste products that we discard every day. As they leave, their message chemical stops pushing up the body's thermostat. The fever cools down. Soon the body gets back to its normal temperature and the patient begins to recover.

Medical research scientists discovered how a fever is caused just a few years ago. But they still do not understand exactly why the body heats itself up to a feverish state. Some experts suspect that certain germs are roasted by the extra heat. But this does not explain all of the feverish story. However, we know for sure that a fever means that the body is fighting a war to defend itself. It is too busy to attend to our everyday comforts. And naturally we want to help it. When fever arrives, every sensible person stays home in bed, sends for the doctor, and obeys his orders.