The phrase "die of sickness" is correct and can be used in written English.
It is typically used to describe someone's cause of death when they passed away due to an illness or disease. Example: The elderly woman had been battling cancer for years, but unfortunately, she eventually died of sickness.
"So many people die in accidents, so many die of sickness.
Artists, writers, musicians, poets, cinema and theater directors all flourished at their crafts while awaiting deportation to the death camps if they didn't die of sickness or malnutrition.
Upon their arrival, Odin threw Jörmungandr into "that deep sea that lies round all lands," Odin threw Hel into Niflheim, and bestowed upon her authority over nine worlds, in that she must "administer board and lodging to those sent to her, and that is those who die of sickness or old age".
He also said that Jiaxing had a designated disposal area for pigs that died of sickness.
My pa died of sickness before I was born and then my ma died, of course, no sur- prises there.
In the countryside, the poverty was so deep and medical care so distant that people often died of sickness and hunger.
He took 200 ships to Cyprus, detaching 60 to help the Egyptian nationalists, but during the siege of the Phoenician city of Citium, he died of sickness or a wound.
Another possibility, some American officers believe, is that Mr. bin Laden, who is 45 if he is still alive, died of sickness at Tora Bora and was buried somewhere in the heights, after the bombing interrupted the dialysis he needed to survive a longstanding kidney condition.
The small Jewish cemetery behind the main hall houses the remains of perhaps 2,000 people who died of sickness and starvation during the winter of 1944-45 as the Hungarian Nazi Arrow Cross ran wild and the Red army steadily advanced, until the ghetto was finally liberated in January 1945.
County Galway death records showed that most of the children buried in the unmarked grave had died of sickness or disease.
In chapter 17, the king Dyggvi dies of sickness.
