VANCOUVER -- The World Health Organization is expressing concern about a jump in COVID-19, or novel coronavirus, cases in Iran — with the latest numbers indicating there have been 18 new diagnoses and four deaths in the last two days. 

That number doesn't include B.C.'s sixth case, a woman in her 30s, who returned to Metro Vancouver from Iran this week after spending several weeks in the country. 

The woman showed mild symptoms when she arrived back in Metro Vancouver and went to hospital where she was tested for the virus. She was sent home where she now remains in isolation after her testing came back with a positive result. The woman lives somewhere in the Fraser Health region.

Some of the woman's close contacts are also in isolation as a precaution, health officials say.

While B.C’s five previous patients had travelled to China or had links to others who had — the latest case is different, with health officials calling it “unusual” given the woman was not in China and appears to have milder symptoms than others. 

"It certainly is what I call a sentinel event, and it means we will be doing a detailed investigation both here in Canada and tracing her travel all the way back to Iran," Dr. Bonnie Henry, provincial health officer, told reporters Thursday. "I expect there will be an international investigation to try and understand where the exposure occurred.

"It's a marker that something may be going on, broader than what we expect."

Health officials say over the next few days they may also be notifying people who were on the same flight as the woman. 

"We are looking at all her movements over the last few days since she’s been home," Henry said.

Earlier this week B.C. health officials revealed that the first COVID-19 patient in the province — a man who had been in Wuhan, China, in January had fully recovered. The other patients were said to be recovering well.

Three of those patients live in the Vancouver Coastal Health Region — with B.C.'s fifth patient, a woman in her 30s who had recently travelled back to Canada from Shanghai — living in the Interior Health region. 

Health officials have continued to say the transmission risk in British Columbia remains low.