Yes; that is possible.
Mozart dided of an an unknown illness after being bedridden for a couple weeks. The exact cause of illness is unknown but involved swelling, pain, and vomiting.
It has been noted that Matthew Flinders suffered greatly from illness. However, history articles about him state it is unknown what his illness was.
he died from an illness that is unknown, or old age
She died from a unknown illness
The treatment is unknown.
No he killed himselg
She died from a unknown illness
Currently an unknown VERY SERIOUS illness.
No, Amerigo died of an unknown illness on his 3rd voyage.
The exact number of young girls with eating disorders is unknown, because approximately 90% of those with the disorder don't seek treatment. Eating disorders cause the most fatalities of any mental illness, so it is imperative that you seek advice from a psychologist who specializes in eating disorder treatment.
George Mason Died of an illness {currently unknown}
Bonnie Lee died from an unknown illness.