Doctors say that so far, kids are hit hardest with the flu. The flu shot is helping keep them out of the hospital.

Classic flu symptoms include fevers, body aches and extreme fatigue.Vera Livchak / Getty Images

Doctors across the country say flu season has arrived earlier than usual and is hitting people - mainly kids, so far - especially hard.

"I don`t think I ever remember seeing it this severe, this soon," said Dr. Suchitra Rao, an infectious disease specialist at Children`s Hospital Colorado in Aurora. "Our emergency department is full of kids coming in with the flu."

Colorado is one of the nation`s current hot spots of flu activity, according to the latest report from the Centers for Disease Control and Prevention.

Michigan, too, is experiencing a marked increase in cases.

"Flu, flu, flu. So much flu," said Dr. Debra Langlois, a pediatrician at University of Michigan Health C.S. Mott Children`s Hospital in Ann Arbor. "We are inundated."

Dr. John Schieffelin, a pediatric infectious disease specialist at Tulane University School of Medicine in New Orleans, is also seeing a surge in bad cases, particularly among kids who haven`t had their flu shots.

"The kids who are vaccinated are doing just fine" recovering at home, Schieffelin said. "It`s the unvaccinated children that we`re seeing in the hospital."

Flu symptoms

Langlois said she and her colleagues are seeing a fair amount of classic flu symptoms: fevers, body aches and extreme fatigue.

Anecdotally, Langlois said that she`s also seeing kids with severe headaches and dizziness. Her 7-year-old daughter had the flu last week and described the feeling like this: "I feel dizzy, like I`m spinning when I`m trying to walk." Dehydration was the likely cause, Langlois said.

Some kids may also experience gastrointestinal issues like vomiting and diarrhea. But those symptoms could also arise because of a secondary virus.

Children who have "persistent" fevers lasting two to three days, Langlois said, should be seen by a doctor.

Is Tamiflu available?

Pharmacies say demand for the antiviral drug Tamiflu is also increasing. When given within the first 24 hours or so of flu symptoms, the drug has been shown to make people feel better about a day earlier than expected.

A Walgreens spokesperson said the pharmacy chain is seeing "very high demand" for Tamiflu nationwide. The company recently saw its supply run low but has since ordered additional stock, the spokesperson said.

According to the Walgreens Respiratory Index - a weekly online tool that tracks the spread of respiratory illnesses - demand for over-the-counter at-home flu tests has jumped 61% nationwide over the last two weeks. In New York state, where flu activity is considered very high, according to the CDC, week over week demand is up 23%, while the two week increase stands at 111%.

Antonio Ciaccia, president of 3 Axis Advisory, a consulting firm focused on addressing supply chain issues, said he`s hearing from a number of independent pharmacies across the U.S. who say they`re struggling to meet demand for Tamiflu.

"We are seeing an early heavy wave of flu cases, which is likely pushing a bit of unexpected pressure on the broader drug distribution channel and its supply," Ciaccia said.

Steve Moore, who runs an independent pharmacy in Plattsburgh, New York, said his primary supplier is not experiencing shortages of Tamiflu. His backup supplier, however, is currently out of stock.

While Tamiflu can be helpful, Langlois said it`s no "miracle cure."

The antiviral is authorized for people 2 weeks and older, and is generally most effective when given within the first 48 hours of flu symptoms.

"The thing to think about for Tamiflu is that it shortens the duration of symptoms by about a day," Langlois said. "It`s really best reserved for high-risk patients, like patients with chronic lung disease, and young kiddos under age 2."

If you`re sick, stay home

"The best thing is prevention," Langlois said, "and that`s getting your flu shot."

The CDC recommends annual flu vaccines for everyone 6 months and older.

Doctors worry that kids who are sick with flu now could spread it to grandparents and other older adults over the holidays.

"At the risk of being a Grinch, if you have the flu and you actively have fevers, then you should stay home. Don`t go to family gatherings," said Dr. Bernard Camins, medical director for infection prevention for Mount Sinai Health System in New York City. "People will understand."