It's the time of sneezing, coughing, hacking and wheezing. Cases of the flu are surging throughout much of the United States as the new year begins.

In its latest Influenza Surveillance Report, published on Dec. 30, the Centers for Disease Control and Prevention reported "high" or "very high" levels of flu activity in 32 states and jurisdictions. From the week before, healthcare providers saw a 6% uptick in patients with respiratory illnesses.

The newest influenza strain, Subclade K (or A(H3N2), J.2.4.1), is a mutation of influenza A. Though data has yet to show that this new strain, penned "super flu," has an "increase in disease severity" compared to previous influenza A strains, the World Health Organization, reports it is a notable evolution.

The CDC continues to encourage folks to get influenza vaccinations, especially children and people who are pregnant.

As the flu season remains underway, here's what to know about common influenza symptoms, including those that require medical attention.

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What are the common flu symptoms?

The most common symptoms of the flu, per the CDC, include:

• Fever

• Cough

• Sore throat

• Runny or stuffy nose

• Muscle or body aches

• Headaches

• Fatigue

• Some people may experience vomiting and diarrhea, but this is more common in children than adults.

What flu symptoms require medical attention

If symptoms prolong, worsen or develop into any of the following, seek medical care right away, the CDC advises.

• Fast breathing, trouble breathing or shortness of breath

• Persistent pain or pressure in the chest or abdomen

• Bluish lips or face, in children

• Persistent dizziness, confusion, inability to arouse

• Dehydration

• Fever or cough that improves then returns or worsens

• Seizures

• Fever about 104 degrees Fahrenheit that isn't controlled by medication

• In children younger than 12 weeks, any fever

• Worsening of chronic medical conditions

What's the difference between the common cold and flu?

The flu and common cold are both respiratory illness, caused by different viruses. The flu is caused by influenza viruses, while the common cold can be caused by varying viruses, including rhinoviruses, parainfluenza and seasonal COVID-19, according to the CDC.

When it comes to symptoms, cold symptoms are milder than those of the flu. People with a cold are more likely to have a runny or stuffy nose, and colds don't tend to result in serious health issues.

Greta Cross is a national trending reporter at USA TODAY. Story idea? Email her at gcross@usatoday.com.

This article originally appeared on USA TODAY: Flu season is here. What are common symptoms to watch for?