Every year, millions of Americans get the flu. You can get the flu at any time of year, but most cases happen during flu season.

The exact dates of flu season change every year, but it typically starts when temperatures start to drop in the fall and ends when they start to rise in the spring. In the northern hemisphere, this generally means flu season runs from October through April.

Flu season in the United States runs from mid-fall to late spring, because the flu virus is more active and spreads faster when temperatures are chilly. The exact months change a little each year.

The Centers For Disease Control and Prevention (CDC) monitors flu cases every year. When cases begin to spike in the fall, the CDC declares the start of flu season. During most flu seasons, the highest number of flu cases are reported between December and February, when temperatures are the lowest and the air is dry.

Although the flu virus can be spread at any time, cases spike when temperature and humidity drop. That’s why flu seasons around the world are associated with the colder temperatures.

While in Canada and most of Europe, temperatures generally fall at about the same time as in the United States, this isn’t the case everywhere. For example, in countries in the southern hemisphere, such as Australia, Thailand, and South Africa, flu season generally runs from April to October.

Just like in the United States, the exact dates of flu seasons around the world change each year.

Many people think of the flu as a mild illness. It’s common for people to say a cough or sneeze is “just the flu.”

However, the flu can actually be a very serious illness. People in high-risk groups can experience serious flu symptoms that can lead to hospitalization and even death. High-risk groups include:

  • young children
  • pregnant people
  • people 65 or older
  • people with asthma
  • people with heart disease
  • people with diabetes
  • people with conditions that impact their immune systems

The flu spreads in respiratory droplets from person to person. Even if you have a mild case, you can pass the flu virus to others. This could include people in high-risk groups.

Flu shots are the best way to prevent the flu and keep you from passing the flu to others. Research has shown that flu shots reduce the risk of illness, hospitalization, and death.

When you think about the flu, you probably think of a single condition, but there are actually different influenza viruses that can lead to the flu. Each year, researchers determine which strains of the flu-causing viruses are likely to be the most common during the upcoming flu season. This research is used to create the flu vaccine for that season. That’s one reason it’s so important to get a flu shot every year.

Flu viruses change all the time, so last year’s shot might not protect you from this year’s viruses. Plus, your immune system’s defenses from the flu shot fade with time, so getting an annual shot is a great way to stay protected.

Often, people assume only people who are over 65 or have weakened immune systems need the flu shot, but that’s not the case. The CDC recommends that everyone over 6 months old get a flu shot every year. This includes children and healthy young adults.

Young children are one of the groups at high risk for flu complications, making an annual vaccine especially important for them.

There are some similarities between the flu and COVID-19. They’re both caused by viruses, both characterized by respiratory symptoms, and both tend to spike when temperatures drop. However, the virus that causes each condition is different.

A flu shot won’t prevent COVID-19, and getting a COVID-19 vaccination doesn’t mean you won’t need a flu shot this year. It’s important to get both vaccines. Plus, by reducing your risk for hospitalization from the flu, you’re reducing the strain on hospitals during the pandemic.

It’s nearly always a good idea to get a flu shot, but there are a few times you shouldn’t. People who shouldn’t get a flu shot include:

  • infants younger than 6 months old
  • people who have severe and life threatening allergies to common vaccine ingredients such as gelatin, eggs, or antibiotics

Other people should talk to their doctor to make sure the flu shot is safe for them. This includes people who:

  • are currently feeling sick
  • have had Guillain-Barré Syndrome in the past
  • have a mild allergy to eggs, gelatin, antibiotics, or any other common flu shot ingredient

The flu is caused by a contagious virus that’s mainly spread when people with the flu cough, sneeze, or talk near another person. The virus can also be spread via contact with surfaces that have been exposed to the virus. For example, sharing a straw with someone when you have the flu could pass the flu virus on to them.

The virus is contagious for a few days before symptoms start to show. This means you can pass the flu before you even know you have it.

Flu symptoms include:

  • fever
  • sore throat
  • cough
  • aches and pain
  • nasal congestion
  • headaches
  • fatigue

Children with the flu might also experience:

  • nausea
  • vomiting
  • diarrhea

Since the flu shares symptoms with many other conditions, it’s not possible to determine whether you have the flu just by looking at symptoms. You’ll need to have a test done to identify the exact cause.

Flu tests are done by swabbing the inside of your nose or the back of your throat. The sample is then tested for influenza viruses. There are a few different types of flu tests available. Some will show results in as little as 10 minutes, while others will take few hours to deliver results.

Often, the flu resolves on its own with rest and over-the-counter treatments. However, sometimes prescription treatment is necessary, especially for people in high-risk groups.

The flu is treated with antiviral medications. Antiviral medication can shorten your flu duration and prevent you from developing serious complications such as pneumonia. Just like the flu vaccine, the recommended antiviral medications for the flu may change each flu season based on the specific flu viruses that are circulating.

Flu season begins in the fall when the weather gets colder and flu cases start to spike. It generally ends in late spring.

While for some people, the flu is a minor illness that can be treated at home, other people can have severe complications that lead to hospitalizations and death.

The best way to protect yourself and the people around you is to get the flu shot each year before the peak of flu season.