More than 1,300 people may have already died from conditions worsened by the flu so far this season, according to a preliminary estimate from the U.S. Centers for Disease Control and Prevention.

The analysis adds that there have been at least 2.6 million flu illnesses and 23,000 flu-related hospitalizations as well. Residents in long-term care and senior living settings are particularly vulnerable, as many have weakened or compromised immune systems, experts say.

Flu activity has been reported nationwide. But 11 states reported high activity levels for the week ending Dec. 7: Alabama, Arkansas, Georgia, Mississippi, Nebraska, New Mexico, South Carolina, Tennessee, Texas, Virginia and Washington.

The uptick in flu activity is largely being caused by influenza B/Victoria viruses, which are atypical for this time of the year.

Fly symptoms include fever, chills, coughing, sore throat, runny or stuffy nose, muscle or body aches, headaches and fatigue. In extreme cases, pneumonia and even death can result.

The CDC recommends that residents and others facing a high risk for developing flu-related complications get treated with antiviral medications as quickly as possible. Early treatment can help reduce symptoms and speed recovery.

In addition to being vaccinated themselves, caregivers are advised to wash hands frequently, and avoid touching their own eyes, noses and mouths.