Editor’s note: A previous version of this story contained incorrect information about the school’s recent dance. The event was held outdoors. The story has been corrected.

SAN DIEGO — A Public Health Services investigation into a large, suspected outbreak of respiratory and flu-like symptoms among students at Patrick Henry High School was announced Wednesday by the San Diego County Communications Office.

According to a County News Center report, the region is seeing a rapid start to flu season while also see daily COVID-19 cases in the hundreds. Due to this, the County says it’s too early to determine a cause to the suspected outbreak.

Nearly half of the students at Patrick Henry High School are home sick, according to the school district.

“About 700 students were absent altogether yesterday at this one high school and a couple hundred more were sent home over the course of the day for having symptoms,” said Dr. Howard Taras, the San Diego Unified School District’s physician consultant.

Dr. Taras said the outbreak happened following the school’s homecoming dance Saturday. That event was held outdoors, the school’s principal confirmed to the district.

“I’m not sure that schools were the place where it was contracted initially,” he stated. “Schools were already beginning to be a bit more empty Monday, and bit more on Tuesday and today even more.”

This comes as Rady Children’s Hospital reports an uptick in flu and respiratory virus-related emergency room visits, the County report cited.

“All the kids are getting together, that’s what kids do, and they are spreading these viruses all at the same time,” said Dr. John Bradley, the medical director of infectious disease at Rady Children’s Hospital.

Dr. Bradley said recently the hospital has seen more emergency room visits because of flu and respiratory syncytial virus, or RSV. It is not a new virus but causing more disease. Bradley said that is because during COVID-19 lockdown kids were not getting exposed to the common viruses and, therefore, could not build up their immunity.

Bradley said, “the number of kids who are susceptible to these viruses is far greater now than the usual year pre-pandemic. So these viruses are spreading thru the community, all of them, with lighting speed.”

The county said no hospitalizations have been linked to the illness investigation at Patrick Henry High School and several tests have come back negative for COVID-19. However, doctors have said the respiratory illnesses and symptoms they are seeing are not life-threatening for most people.

“Other than the fact that these kids are all getting sick, these viruses are not dangerous like COVID,” Bradley said. “There is no post infection inflammation that prevents you from getting oxygen into your blood stream. These are just really bad chest colds.”

The school district and county have said as of Wednesday it is too early to tell what caused the outbreak or what virus exactly is infecting students.

“We are coordinating with local school districts and are checking with other school campuses to try and figure out why so many students have been affected so suddenly,” said Cameron Kaiser, M.D., M.P.H., County deputy public health officer. “Unfortunately, we anticipated this would be a rough influenza season, and alongside COVID-19 other respiratory viruses are also making a rapid comeback.”

It’s unknown at this time whether other schools in the area are experiencing similar outbreaks. A County investigation is ongoing.

In the meantime, health officials are encouraging the public to avoid getting sick by following these steps:

-Thoroughly wash hands often and/or use hand sanitizers.

-Avoid being around people who are experiencing symptoms of illness.

-Clean common areas and surfaces.

-If you are sick, stay home.