The number of confirmed Covid-19 cases has more than tripled in Marin over the past week, and that likely represents just a tiny fraction of the actual cases. Around 1 percent—or 3,000 residents—have been infected with the coronavirus, Dr. Lisa Santora, the deputy health officer, estimated on Tuesday. “Some have recovered, some are asymptomatic, and some think they just have allergies,” she said. Testing capacity is limited. Out of 527 tests administered at Marin’s drive-through testing site, 53 were positive; five of those patients were hospitalized. Health officials who have also been tracking reports of respiratory illness have not reported an increase. Dr. Santora said we are in week two of a 12-week epidemic curve, with a peak coming around week six. “We still have a long way to go,” she said. The coronavirus’s presence in Marin was highlighted when Dr. Matt Willis, the county’s top health official, tested positive for Covid-19 last week. He is quarantined at home, recovering from a cough and a fever, and will return to work three days after his symptoms subside. In the meantime, Dr. Santora is taking the lead in providing daily video updates on the county’s coronavirus response. No patients have died in Marin; in the United States, the virus has claimed at least 900 lives, including 60 deaths in California.