WASHINGTON (AP) _ Lyme disease, a tick-borne illness that is difficult to diagnose, has been reported in 43 states and will soon reach five more, a panel predicted Monday.

''Lyme disease is one of the most rapidly growing diseases in the United States'' that are spread by carriers other than humans, said Dr. Steven Hausman, who is with the National Institute of Arthritis and Musculoskeletal and Skin Diseases.

Hausman spoke at a news conference, along with two members of Congress and a Connecticut family struck by the illness, to mark Lyme Disease Awareness Week, which began Monday.

Lyme disease, which is caused by a bacterium, is spread by the common deer tick. Symptoms usually start with a circular rash, and include fever, chills, fatigue, aching and stiffness. Paralysis may follow.

While most of the known cases have been concentrated in the Northeast - particularly Connecticut and Suffolk and Westchester counties in New York - Lyme disease was reported last year in every continental state except Montana, Wyoming, Nebraska, Arizona and New Mexico.

''We won't stop the ticks - they're in 43 states already and soon they'll be in 50,'' said Rep. George Hochbrueckner, D-N.Y.

There were nearly 14,000 reported cases in 1988, but ''we fear this is a very low number,'' said Sen. Joseph Lieberman, D-Conn.

In 1987, there were only 5,800 reported cases, but much of the jump was due to better reporting, said Dr. Stephen Heyes, director of the office of disease prevention at the National Institutes of Health.