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Influenza also known as the flu, is a contagious viral respiratory illness, caused by influenza viruses. Symptoms can cause mild to severe illness. Serious outcomes of flu infection can result in hospitalization or death. Some people, such as older people, young children, and people with certain health conditions, are at higher risk for serious flu complications.


For most people, influenza resolves on its own. But sometimes, influenza and its complications can be deadly. People at higher risk of developing flu complications include:

  • Young children under 5, and especially those under 2 years.
  • Adults older than 65.
  • Residents of nursing homes and other long-term care facilities.
  • Pregnant women and women up to two weeks postpartum.
  • People with weakened immune systems.
  • People who have chronic illnesses, such as asthma, heart disease, kidney disease and diabetes.
  • People who are very obese, with a body mass index (BMI) of 40 or higher.

The CDC recommends that your best defense against influenza is to receive an annual vaccination. USA EBN does not endorse this recommendation. Everyone's body and body chemistry is different. Annual vaccination may work for most, but there is a small percentage of people, who should not take the vaccination. You are your own best doctor, educate yourself on your own "body talk" and make the decision that is best for you.

When is the flu season in the United States?

In the United States, flu season occurs in the fall and winter, Late October through March. The peak of flu season is February, according to the CDC.

But you can get the flu at any time of the year.

You’re more likely to get sick during the fall and winter months. This is because you’re spending more time in close quarters with other people. And because you’re exposed to lots of different illnesses.

You’re more likely to catch the flu if you already have a different infection. This is because other infections can weaken your immune system and make you more vulnerable to new ones.

The overall health impact (infections, hospitalizations, and deaths) of a flu season varies, from year to year. CDC monitors circulating flu viruses and their related disease activity and provides influenza reports each week from October through May. Flu surveillance in the U.S. continues through the summer months with condensed reports.

How many people get sick or die from the flu every year?

Flu seasons vary in severity depending on a number of factors including the characteristics of circulating viruses, the timing of the season, how well the vaccine is protecting against influenza infection, and how many people got vaccinated.. While the numbers vary, in the United States, millions of people are sickened, hundreds of thousands are hospitalized and thousands or tens of thousands of people die from flu every year. The sad part about these numbers is that most of the flu cases is preventable.

Is the “stomach flu” really the flu?

Many people use the term “stomach flu” to describe illnesses with nausea, vomiting or diarrhea. These symptoms can be caused by many different viruses, bacteria or even parasites. While vomiting, diarrhea, and being nauseous or “sick to your stomach” can sometimes be related to the flu — more commonly in children than adults — these problems are rarely the main symptoms of influenza. The flu is a respiratory disease and not a stomach or intestinal disease.

Do other respiratory viruses circulate during the flu season?

In addition to the flu virus, several other respiratory viruses also can circulate during the flu season and, can cause symptoms and illness similar to those seen with flu infection. These non-flu viruses include rhinovirus, (one cause of the "common cold") and respiratory syncytial virus (RSV), which is the most common cause of severe respiratory illness, in young children, as well as a leading cause of death from respiratory illness, in those aged 65 years and older.

Is there such a thing as the “24-hour flu”?

The “24-hour flu” is a common infection that has nothing to do with influenza, despite sharing a name. The 24-hour flu is caused by a family of viruses called norovirus.

The symptoms of a norovirus infection include:




stomach cramping

These symptoms occur in the gastrointestinal system. That’s why the 24-hour flu is sometimes called a “stomach flu.” Although it’s called the “24-hour flu,” you may be ill up to three days.

Influenza (or the flu) is a respiratory illness. It causes symptoms in the respiratory system.

Symptoms of influenza include:




runny nose

body aches

The symptoms of the two are different. Some people with the flu may experience nausea and vomiting while they’re sick. But these symptoms aren’t as common.

What’s the difference between a cold and the flu?

The common cold and the flu may seem similar at first. They are both respiratory illnesses and can cause similar symptoms. But different viruses cause these two conditions. Your symptoms will help you tell the difference between the two.

Both a cold and the flu share a few common symptoms. People with either illness often experience:

  1. a runny or stuffy nose
  2. sneezing
  3. body aches
  4. general fatigue

As a rule, flu symptoms are more severe than cold symptoms.

Another distinct difference between the two is how serious they are. Colds rarely cause other health conditions or problems. But the flu can lead to sinus and ear infections, pneumonia, and sepsis.

To determine whether your symptoms are from a cold or from the flu, you need to see your doctor. Your doctor will run tests that can help determine what’s behind your symptoms.

If your doctor diagnoses a cold, you’ll only need to treat your symptoms until the virus has run its course. These treatments can include using over-the-counter (OTC) cold medications, staying hydrated, and getting plenty of rest.

Taking an OTC flu medicine early in the virus’ cycle may also help. Rest and hydration are also beneficial for people with the flu. Much like the common cold, the flu just needs time to work its way through your body.

What are the symptoms of the flu?

Common symptoms of the flu include:

Fever: The flu almost always causes an increase in your body temperature. This is also known as a fever. Most flu-related fevers range from a low-grade fever around 100°F (37.8°C) to as high as 104°F (40°C). Although alarming, it’s not uncommon for young children to have higher fevers than adults. If you suspect your child has the flu, see your doctor.

You may feel “feverish” when you have an elevated temperature. Symptoms include chills, sweats, or being cold despite your body’s high temperature. Most fevers last for less than one week, usually around three to four days.

Cough: A dry, persistent cough is common with the flu. The cough may worsen, becoming uncomfortable and painful. You may also experience shortness of breath or chest discomfort during this time. Many flu-related coughs can last for about two weeks.

Muscle aches: These flu-related muscle pains are most common in your neck, back, arms, and legs. They can often be severe, making it difficult to move even when trying to perform basic tasks.

Headache: Your first symptom of the flu may be a severe headache. Sometimes eye symptoms, including light and sound sensitivity, go along with your headache.

Fatigue: Feeling tired is a not-so-obvious symptom of the flu. Feeling generally unwell can be a sign of many conditions. These feelings of tiredness and fatigue may come on fast and be difficult to overcome.

How long does the flu last?

Most people will recover from the flu in about one week. But it may take several more days for you to feel back to your usual self. It’s not uncommon for you to feel tired for several days after your flu symptoms have subsided.

It’s important you stay home from school or work until you haven’t had a fever for at least 24 hours. This is without taking fever-reducing medications. If you have the flu, you’re contagious a day before your symptoms appear and up to five to seven days afterward.

What causes the flu?

The flu is a virus that’s shared in several ways. First, you can pick up the virus from being near a person who has the flu and sneezes, coughs, or talks.

The virus can also live on inanimate objects for two to eight hours. If someone with the virus touched a common surface like a door handle or a keyboard, and you touch the same surface, you could get the virus. Once you have the virus on your hand, it can enter your body by touching your mouth, eyes, or nose.

You can vaccinate against the flu. An annual flu vaccine helps your body prepare for exposure to the virus. But flu viruses are morphing and changing. That’s why you need the flu shot every year. A flu shot helps you by activating your immune system to make antibodies against particular strains of the virus. Antibodies are what prevent infections.

It’s possible to get the flu after receiving the flu shot if you come into contact with other strains of the virus. Even then, it’s likely your symptoms will be much less severe than if you hadn’t had the vaccine at all. This is due to cross-protection. This means that different strains share common elements. And that allows the flu vaccine to work against them, too.

How does CDC monitor the progress of the flu season?

CDC collects data year-round and reports on influenza (flu) activity in the United States each week from October through May. The U.S. influenza surveillance system consists of five separate categories.

  • Laboratory-based viral surveillance, which tracks the number and percentage of influenza-positive tests from laboratories across the country, and monitors for human infections with influenza A viruses that are different from currently circulating human influenza H1 and H3 viruses.
  • Outpatient physician surveillance for influenza-like illness (I L I), which tracks the percentage of doctor visits for flu-like symptoms.
  • Mortality surveillance as reported through the 122 Cities Mortality Reporting System, which tracks the percentage of deaths reported to be caused by pneumonia and influenza, in 122 cities in the United States, and influenza-associated pediatric mortality, as reported through the Nationally Notifiable Disease Surveillance System, which tracks the number of deaths in children with laboratory confirmed influenza infection.
  • Hospitalization surveillance, which tracks laboratory confirmed influenza-associated hospitalizations in children, and adults through the Influenza Hospitalization Network and, the Aggregate Hospitalization and Death Reporting Activity.
  • State and territorial epidemiologist reports of influenza activity, which indicates the number of states affected by flu and, the degree to which they are affected.

These surveillance components allow CDC to determine when and where, influenza activity is occurring, determine what types of influenza viruses are circulating, detect changes in the influenza viruses collected and analyzed, track patterns of influenza-related illness, and measure the impact of influenza in the United States. All influenza activity reporting by states, laboratories, and health care providers is voluntary.

Why is there a week-long lag between the data and when it’s reported?

The influenza surveillance system is one of the largest and, most timely surveillance systems at CDC. The system consists of 5 complementary surveillance categories. These categories include reports from more than 145 laboratories, about 3,000 outpatient health care providers, vital statistics offices in 122 cities, research and health care personnel at the Emerging Infections Program (E I P) sites, and influenza surveillance coordinators and state epidemiologists from all 50 state health departments, and the New York City and District of Columbia health departments.

Influenza surveillance data collection is based on a reporting week that starts on Sunday and ends on Saturday of each week. Each surveillance participant is requested to summarize weekly data and submit it to CDC, by Tuesday afternoon of the following week. The data are then downloaded, compiled, and analyzed at CDC each Wednesday. The compiled data are interpreted and checked for anomalies which are resolved before the report is written and submitted for clearance at CDC. On Friday the report is approved, distributed, and posted on the Internet.