Influenza cases have risen sharply across the Unites States this cold & flu season, and it continues to remain widespread in 49 states, according to the Centers for Disease Control.

This year's aggressive strain, H3N2 (also known as the "Hong Kong flu"), is the worst in nearly a decade, and has already claimed multiple lives, including adults and children who had no underlying health conditions.

The virus is on track to match the 2014-15 flu season, which saw 34 million Americans infected. Approximately 710,000 of them were hospitalized, and about 56,000 died.

"We'll expect something around those numbers," Dr. Daniel B. Jernigan, director of the C.D.C.'s influenza division, said in a telephone news conference.

Although everyone is at risk of contracting influenza, it's higher for those with weaker immune systems, specifically, children and the elderly.

As you already know, people with the flu often experience runny or stuffy nose, coughs, fever, chills, headaches, fatigue, and body aches. Children tend to also have diarrhea and/or vomiting.

However, there is reportedly another surprising symptom that tends to go unnoticed.

When Brodi Willard's son, Seb, was diagnosed with Influenza after exhibiting this unusual symptom, she was caught off guard. Now, she's sending out a warning to other parents so they can be on the lookout.

According to a Facebook post written by Willard, her son did not have any unusual symptoms when he left for school in the morning. However, when he came home, he had hives.

"Every time he would scratch, more would appear. We tried changing his clothes and giving him a bath, but nothing helped."

Like any concerned parent would do, Willard called Seb's pediatrician, but she was not expecting what came next.

"They said they had two kids come into the office that day with the same symptoms and tested POSITIVE FOR INFLUENZA," Willard recalled.

The following morning, Willard took her son to the doctor where he was diagnosed with Influenza B. Willard explained that Seb had "NO symptoms. No fever, no cough, and no runny nose. He only has hives."

"Please keep watch on your children so if they develop hives, please call your pediatrician," Willard advised. "I have never heard of this symptom but it is obviously something to be on the lookout for."

Willard's post has since gone viral with over 250,000 shares and 15,000 comments from concerned parents, who expressed their gratitude for the heads up.

Dr. Julie Linderman from Inwood Village Pediatrics in Dallas spoke to WFAA and confirmed that hives are not a common symptom of the flu, but they may occur if an infected individual has "an allergic type of reaction to a virus."

In addition to Dr. Linderman's comments, Children's Health Dallas released a statement.

"Hives are not typically associated with the flu. Testing positive for flu in the absence of typical or classical flu symptoms could suggest that the tests are giving false positive results."

Do you think hives are an uncommon symptom of the flu? Let us know in the comments!