St. Louis ? Lab tests indicate that a St. Louis woman died of the West Nile virus, a disease that came on suddenly and claimed her life quickly, the woman’s grandson said Monday.

Cora Walton, 75, of St. Louis, is the first Missourian to die of the virus since it first appeared in Missouri last year. She died Aug. 7.

St. Louis Health Department chief Mike Thomas announced the death Monday but did not release Mrs. Walton’s name. State health officials said an independent lab test showed that Mrs. Walton tested positive for West Nile, but officials were still awaiting confirmation from the Center for Disease Control and Prevention.

Mrs. Walton’s grandson, Sean Walton, a technician in the St. Louis office of The Associated Press, confirmed that his grandmother died of the virus.

Sean Walton said his grandmother seemed fine when they spoke four days before her death. “And all of a sudden, two days later, it was like she didn’t know anyone,” he said.

Seven Missourians have now tested positive for West Nile six in the St. Louis area and one in Washington County in southeast Missouri.