The phrase "a third case of" is correct and usable in written English.
It can be used when referring to the occurrence of a specific event or situation for the third time.
Example: "The health department reported a third case of the flu in the community this week."
Alternatives: "the third instance of" or "the third occurrence of".
The Wesley Hospital in Brisbane is investigating a third case of legionnaires' disease, after one patient died and another was put in intensive care last week.
The two defendants were acquitted in a third case of the killing of a security officer due to a lack of evidence.
A third case of the disease, involving a California man who died in May, may also have been connected to potting soil, the Centers for Disease Control and Prevention said.
Pakistan confirmed a third case of a fast-moving strain of polio this month, in an 8-month-old boy in the southern port city of Karachi, bringing the total cases in the country this year to 18.
A third case of oseltamivir-resistant swine flu, announced today in Hong Kong, has flu experts worried that resistance to the drug is spreading.
Hit with a report of a third case of polio in northern Nigeria, leaders of the global eradication effort are asking themselves how they could have been so terribly wrong about the country.
"And I said, 'All right, we'll get more.' " As recently as a decade ago, researchers could spend years trying to find a second case of a newly discovered disease.
A second case of polio was confirmed in Indonesia and more are expected, the Health Ministry said.
Veterinary authorities confirmed a sixth case of mad cow disease, in Rimavska Seca.
A second case of bejewelled bows illustrate the mode for bodice ornaments in the 17th century.
A second case of an infected cow was discovered last week and wholesale prices for beef have dropped by 20percentt.
