Health experts are sounding the alarm as flu activity surges nationwide, with most states reporting high or very high levels.The Centers for Disease Control and Prevention estimates at least 7.5 million Americans have gotten sic k from the flu this season. The agency reports the illness has led to 3,100 deaths so far, including eight children.RELATED STORY | Flu cases are rising. Heres whats driving the surge and how to protect yourselfThere were 5.6 flu-related hospital admissions for every 100,000 people last week, up from 3.1 the week before, according to the CDC. Flu accounted for 5.4% of all hospitalizations last week, compared with 3.2% during Christmas week last year.A new variant, called subclade K, appears to be driving most cases.This strain was not included in this seasons flu vaccine because it was identified after scientists selected the vaccine components. Health officials still advise getting vaccinated.RELATED STORY | What is subclade K? The fast-spreading flu type drawing concern ...read more read less