The winter COVID-and-flu season is ramping up in California and nationwide, with doctors and other experts saying the worst of the respiratory illness season is still to come.

New data show pronounced recent jumps in the rate at which coronavirus and flu tests are coming back positive, as well as the number of hospital-admitted patients testing positive for the viruses. Workplaces are also seeing higher numbers of employees call in sick due to infections.

National wastewater data suggest this winter could see the highest number of coronavirus infections occurring during any given week since the first Omicron wave began in fall 2021.