More than 4 million people are bitten by dogs and cats each year. And orthopedic surgeon Dr. Stephen Kennedy said all bites to the hand should receive medical care, although he says most people are reluctant to see a doctor.

Animal saliva contains a broad range of bacteria. Adult dog jaws, especially among larger breeds, can bite with a force of more than 300 pounds, and when combined with the variety and sharpness of their teeth can cause significant injuries to hand and finger ligaments, tendons, and bones.

Cats do not have the jaw strength of dogs, but their sharp, narrow teeth also can cause serious injury. Up to half of cat bites get infected.

Signs of infection:

•  Redness

•  Swelling

•  Pain that worsens

•  Fever

If a bite occurs:

• Inspect the hand carefully for any puncture wounds. Even a small wound can inject lethal bacteria under the skin.

•  If there is a puncture wound of any size, wash it as soon as possible with soap and water. Then seek medical advice.

•  Get immediate medical attention if you see redness, feel increasing pain over time, or see red streaking up the hand or arm (or along a tendon). These are signs of a serious infection.

Antibiotics are often given to reduce the chance of infection. More serious bites may need surgery to clean the wound.