Every day, almost 2,200 American health workers stick themselves with needles, often after injecting or drawing blood from a sick patient.

Now, medical equipment manufacturers are designing devices to make such needle sticks -- and the accompanying risk of spreading hepatitis B or even AIDS -- virtually impossible.

One company, ICU Medical Inc. of Mission Viejo, Calif., last week introduced a line of products designed to prevent such accidents.

Needle sticks often occur as a nurse or technician tries to replace the needle's plas- tic cap after use, much as one might miss while putting the cap on a ballpoint pen. One of the new devices, pictured here, has a sheath that goes into place automatically from behind.

There have been four recorded U.S. cases of AIDS infection being transmitted by accidental needle sticks, according to the Centers for Disease Control. None of the four people has developed the disease. With hepatitis, however, the risk is greater. A health worker in close contact with blood and needles has three to five times the normal risk of contracting the serious liver ailment.

Dr. Ronald Hershow, a CDC epidemiologist, said a number of designs for needles have been tried, but so far they have been inconvenient and none has been widely accepted.

The CDC's standing recommendation is that health care workers should never try to recap needles but should dispose of them immediately after use.

Hepatitis B can also by prevented by vaccine, but most health workers have not been vaccinated.