The flu has arrived in Clark County — and it came a little early.Flu activity increased countywide at the end of October, and this week, PeaceHealth Southwest Medical Center is reporting a big jump in positive flu tests.“In the past two weeks we’ve seen a spike in positive results for influenza,” said Catherine Kroll, infection prevention specialist at PeaceHealth Southwest, in a news release. “We’ve gone from a baseline of zero confirmed cases to our current level of about 50 percent positive for those admitted to the hospital.”For the week ending Oct. 29, more than 10 percent of influenza tests in Clark County came back positive — a threshold health officials use to determine when flu transmission is occurring in the community. That week, 12.8 percent of tests came back positive. The following week, which is the most recent county data available, Clark County had a flu test positivity rate of nearly 7 percent.The flu strain sickening people locally appears to be mainly influenza A virus — a strain included in this year’s flu shot.The increase in positive flu tests means PeaceHealth Southwest is implementing patient and visitor restrictions.The hospital asks that nobody who is sick — fever greater than 100 degrees, plus cough or sore throat — visit patients. In addition, the number of visitors should be limited to two family members.In hospital special care units — adult intensive care unit, cardiovascular intensive care unit, family birth center and neonatal intensive care units — additional limitations are in place. In those units, visitors must be 12 or older (except for siblings) and immediate family members (children and significant others). Some units may also implement visiting hour restrictions.