Flu is gaining ground in Colorado, with 46 people hospitalized last week as cases and other indicators rise, state epidemiologist Dr. Rachel Herlihy said. The state’s overall level of respiratory virus activity remains low, according to the Colorado Department of Public Health and Environment. But flu hospitalizations have increased each week since late August, when one person was hospitalized. Herlihy also cited rising test positivity and emergency department visits. “The numbers are still small, but do demonstrate that influenza is here and is increasing,” she said. Herlihy urged Coloradans to get vaccinated against flu and COVID-19 now. Protection takes a couple of weeks to build, and respiratory syncytial virus, or RSV, may begin circulating within weeks. Vaccines are available at clinics and pharmacies, including at no or low cost, according to state health officials. The flu virus currently predominant in Colorado is the strain used to make this season’s vaccine, Herlihy said, which could support the vaccine’s effectiveness. The timing matters after two difficult flu seasons. More than 5,900 Coloradans were hospitalized with flu last season, including nearly 1,200 children. In the week between Christmas and New Year’s, about 800 people were hospitalized — a record for that week, according to state figures. COVID-19 is also circulating. State wastewater monitoring has shown rising levels of the virus in nearly all utilities reporting data over the past couple of weeks. Wastewater trends can provide an early signal of infection levels; a study by state health department researchers and the Colorado School of Public Health found the monitoring was among the most reliable real-time indicators for anticipating demand for hospital beds. COVID hospitalizations reached 43 people in mid-September, the highest level since March, then declined. Herlihy said COVID trends may be stabilizing, and that rising wastewater signals have not translated into high hospitalization or death counts so far. Dr. Michelle Barron, an infectious diseases physician at UCHealth, recommends flu and COVID shots for people six months and older, with particular concern for young children, adults over 65 and pregnant people. Vaccination may not prevent every infection, she said, but can reduce the risk of severe illness and hospitalization. Barron also said COVID vaccination can help prevent long COVID, which can cause symptoms including headaches, brain fog and heart problems, and can affect children as well as adults.