Common cold viruses continue to rise heading into spring, CDC data shows. What to know.

If it feels like you've been fighting one illness after another the last few months, you’re not alone.

New surveillance data from the Centers for Disease Control and Prevention shows cold and stomach viruses have carried their winter reign into spring.

The agency’s National Respiratory and Enteric Virus Surveillance System shows positive testing for norovirus, respiratory adenovirus and human parainfluenza viruses have all been steadily increasing the past few weeks.

Americans may be surprised by how much sickness is lingering as the weather warms. But experts say it's not that unusual this time of year.

"Throughout the winter we see these waves where people get more viral illnesses and that may quiet down for a period, and then pick up again during spring," said Dr. Joseph Khabbaza, pulmonary and critical care physician at the Cleveland Clinic.

In a statement sent to USA TODAY, the CDC confirmed an increase in human coronaviruses that do not cause COVID-19 but said the rates remained within expected ranges. However, people may be caught off-guard after years of low viral transmission during the pandemic.

"I was very happy to not get sick the past couple of years, but the past year I’ve returned to the usual annoying respiratory illnesses that linger," Khabbaza said. "Now that we’re over a year from when COVID was ravaging a lot of people, this will give us some sense of a what a future new normal would be from regular respiratory viruses."

Here's what you should know about the viruses making the rounds.

Norovirus

Norovirus, sometimes called the stomach flu or stomach bug, is “very contagious” and typically causes vomiting and diarrhea, according to the CDC. It can be transmitted by having contact with an infected person, consuming contaminated food or water, or touching contaminated surfaces and putting unwashed hands in your mouth.

Adenovirus

Adenoviruses most commonly cause respiratory illness, according to the agency, which range in severity from a cold to pneumonia, croup or bronchitis. There are more than 50 types of adenoviruses that can cause infections in humans and they’re relatively resistant to common disinfectants.

Parainfluenza virus

There are four types and two subtypes of human parainfluenza viruses, also known as HPIVs, the CDC said. The most common types are HPIV-1 and HPIV-2, which are associated with croup, upper and respiratory illnesses, and cold-like symptoms including fever, runny nose, cough, sneezing and sore throat. HPIV-3 is most associated with bronchiolitis, bronchitis and pneumonia in some people. The CDC’s surveillance system shows HPIV-2 and HPIV-3 slightly increasing.

Common cold treatment

There are no specific vaccines or antivirals to prevent and treat these viral infections, but the Mayo Clinic says here are some ways to take care of yourself at home:

  • Stay hydrated with water, juice, clear broth or warm lemon water. Stay away from alcohol or caffeine, which could make dehydration worse.

  • Soothe a sore throat by gargling saltwater – ¼ to ½ teaspoon of salt dissolved into an 8 ounce glass of water.

  • Combat a stuffy nose and congestion with over-the-counter nasal drops or sprays.

  • Sip warm liquids such as warm apple juice or tea and try adding honey to help with a cough.

  • Rest!

For noroviruses, or the stomach bug, it’s important to keep hydrated and replenish fluids lost from vomiting or diarrhea, the CDC said. Severe dehydration could lead to hospitalization.

How long does a common cold last?

The Cleveland Clinic says the common cold lasts seven to 10 days:

  • Days 1 to 3: This is the early stages of the cold. You might start coughing or sneezing, and feeling a runny or stuffy nose.

  • Days 4 to 7: Get ready because the cold is revving up. You might start to feel those body aches, get a headache, or even run a fever. You'll also start feeling more tired and that runny or stuffy nose won't let up.

  • Days 8 to 10: The cold is finally starting to wind down. While you might start feeling better, some symptoms may continue like a persistent coughing that can last up to two months after the initial infection.

If symptoms worsen after 10 days, the Cleveland Clinic suggests consulting a doctor in case you may have developed another infection or complication.

Is it allergies?

It could be! Spring arrived three weeks earlier than usual in several Southeastern states this year. In the mid-Atlantic and northeast regions, it arrived nearly four weeks ahead of schedule.

"A very mild cold can feel a lot like allergies, so that can be hard to differentiate," Khabbaza said. "Luckily, whether you know the difference or not, it wouldn’t tremendously change your approach" to treatment.

Break out the Kleenex! Spring arrives weeks early, bringing sniffling and sneezing to allergy sufferers

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Contributing: Janet Loehrke, USA TODAY. Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: Common cold: CDC data shows steady rise in cases heading into spring