A Vancouver high school student is among the four new cases of H1N1 flu virus identified in British Columbia on Friday.
Staff at Killarney Secondary School sent home a note to parents Friday notifying them that a student tested positive, but is now recovering well at home.
School principal Jill Phillipchuk told CTV News the school will remain open because the risk to students is very low.
Phillipchuk says the boy caught the so-called swine flu from a relative who was recently travelling in Mexico.
Anne Marie D'Angelo from Vancouver Coastal Health Authority says the incubation period for the virus is one to three days, but can last up to seven days.
The letter sent home to parents stated that anyone exposed to the student would have likely become sick by April 30.
Two schools in B.C. have been shut down over virus fears.
Health officials shut down Decker Lake Elementary School near Burns Lake after more than 20 students called in sick Friday.
No students have tested positive for the virus, but spokesperson Ernie Mannering said officials will keep the Northern B.C. school closed this weekend while the Northern Health Authority investigates.
On Thursday, health officials Health closed a Vernon elementary school after a student tested positive for H1N1.
The student from the 800-student Beairsto Elementary School in the North Okanagan is said to be suffering only a mild case of the flu and is at home recovering.
Meanwhile, Liberal Leader Gordon Campbell joined provincial health officials Friday at the B.C. Centre for Disease Control to provide an update on the 15 cases of H1N1 flu in the province.
"All of them are relatively mild, and they are unlike the severe cases that are seen in Mexico," Campbell said.
He said all were either recovering, or already recovered, but expects the number of B.C. cases to rise -- some of which may turn out to be fatal.
Provincial health officer Perry Kendall made an appeal for the people of British Columbia to remain calm, saying "information is our best vaccination."
"It's our best vaccination against fear, our best vaccination against panic," he said.
"It is important to be vigilant but not fearful at this time."
Three of the four new cases reported Friday are secondary cases. This means people caught the virus from someone who had travelled to Mexico, but had not been there themselves. The fourth case was someone who had recently been in the country.
