Local schools are seeing an increase in COVID-19 cases, mirroring trends seen throughout Santa Clara County and in many parts of the country.

The Mountain View Los Altos Union High School District has recorded 69 students testing positive so far this week, according to the district's data dashboard. That's the highest number of weekly cases in the 4,500-student high school district since January. Ten staff members have also tested positive this week.

Over in the Mountain View Whisman School District, Superintendent Ayinde Rudolph announced last week that masks would remain required indoors through the end of the school year. The district originally removed its mask requirement in late March, but reinstated it a month later after the district identified a case of on-campus COVID-19 transmission.

"Since we reinstituted masking on April 26, we have not seen community spread within a classroom as we did when we were unmasked," Rudolph wrote in a May 13 letter to parents. "I know that we all wanted to be 'done' with masks, but we just aren't there yet."

The 4,500-student district, which has recorded 38 students and five staff members testing positive in the last seven days, is one of the few locally to have a masking requirement. Most other districts dropped their mask mandates in mid-March and haven't reinstated them since.

The increasing prevalence of COVID-19 is being felt throughout the community. Santa Clara County is currently reporting an average of 827 new cases per day, a rate more than five times higher than in the trough of mid-March, when fewer than 150 new cases were being reported on average each day.

Health officials say that the increase is due to the spread of highly contagious omicron subvariants and that the actual number of cases is likely higher than those reported because of the use of home test kits. The Santa Clara County Public Health Department is urging the public to wear masks indoors and get tested if they feel sick.

In the Los Altos School District, which has 3,300 students, 41 have tested positive so far this week. That's down from 54 last week, but up substantially from the single-digit cases that the district was seeing in late-March and early-April.

Over in the Palo Alto Unified School District, 131 students and 22 staff members reported positive tests last week. That's the highest number since January and continues a pattern of rising cases that the district has been experiencing since students returned from spring break last month. The district has roughly 10,500 students.