Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

Child’s Death From Mysterious Illness Under Investigation

Health officials are investigating after a mysterious polio-like illness killed a child in Washington state and has affected dozens across the United States.

Last month, 6-year-old Daniel Ramirez arrived at Seattle Children’s Hospital with an unknown virus that caused his brain to swell. Doctors put him in a medically-induced coma in an effort to help his brain heal, but his family said Monday that he had died, CBS News reported.

State and federal health officials believe this may be a case of a rare paralysis-causing condition called acute flaccid myelitis (AFM), which is on the rise among children in the U.S.

So far this year, there have been 89 confirmed cases of AFM in 33 states and most of those patients have been children, according to the Centers for Disease Control and Prevention. Last year, there were 21 cases nationwide.

Health officials are concerned about, but don’t know what’s behind, the rising numbers.

“The CDC is concerned about the increase in cases, so we’re actively investigating the cases and working really closely with health departments on it. We’re intensifying our efforts to find out what causes it — we don’t know what causes it,” CDC pediatrician Dr. Manisha Patel recently told CBS News.

AFM — which can affect people of all ages — impacts the nervous system, specifically the spinal cord. There are a number of causes, including viral infections.

Symptoms include sudden limb weakness, trouble with eye movement, drooping facial muscles and eyelids, difficulty swallowing, slurred speech, and urination problems, CBS News reported.

While there has been an increase in the number of AFM cases, the illness is still very rare, the CDC emphasizes.