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| Influenza (flu): Symptoms and Causes |
For most people, the flu 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 age 5, and especially those under 6 months
- Adults
older than age 65
- Residents
of nursing homes and other long-term care facilities
- Pregnant
women and women up to two weeks after giving birth
- People
with weakened immune systems
- Native
Americans
- People
who have chronic illnesses, such as asthma, heart disease, kidney disease,
liver disease, and diabetes
- People
who are very obese, with a body mass index (BMI) of 40 or higher
Though the annual influenza vaccine isn't 100% effective, it's still your best defense against the flu.
Symptoms of Influenza
At first, the flu may seem like a common cold with
a runny nose, sneezing, and sore throat. But colds usually develop slowly,
whereas the flu tends to come on suddenly. And although a cold can be a bother,
you usually feel much worse with the flu.
Common signs and symptoms of the flu include:
- Fever
- Aching
muscles
- Chills and
sweats
- Headache
- Dry,
persistent cough
- Shortness of
breath
- Tiredness and
weakness
- Runny or
stuffy nose
- Sore throat
- Eye pain
- Vomiting and
diarrhea, but this is more common in children than in adults
When to see a doctor
Most people who get the flu can treat themselves at
home and often don't need to see a doctor.
If you have flu symptoms and are at risk of
complications, see your doctor right away. Taking antiviral drugs may reduce
the length of your illness and help prevent more serious problems.
If you have emergency signs and symptoms of the
flu, get medical care right away. For adults, emergency signs and symptoms can
include:
- Difficulty
breathing or shortness of breath
- Chest pain
- Ongoing
dizziness
- Seizures
- Worsening of
existing medical conditions
- Severe
weakness or muscle pain
Emergency signs and symptoms in children can
include:
- Difficulty
breathing
- Blue lips
- Chest pain
- Dehydration
- Severe muscle
pain
- Seizures
- Worsening of
existing medical conditions
Causes of Influenza
Influenza viruses travel through the air in droplets when
someone with the infection coughs, sneezes, or talks. You can inhale the
droplets directly, or you can pick up the germs from an object — such as a
telephone or computer keyboard — and then transfer them to your eyes, nose, or
mouth.
People with the virus are likely contagious from about a day
before symptoms appear until about five days after they start. Children and
people with weakened immune systems may be contagious for a slightly longer
time.
Influenza viruses are constantly changing, with new strains
appearing regularly. If you've had influenza in the past, your body has already
made antibodies to fight that specific strain of the virus. If future influenza
viruses are similar to those you've encountered before, either by having the
disease or by getting vaccinated, those antibodies may prevent infection or
lessen its severity. But antibody levels may decline over time.
Also, antibodies against influenza viruses you've encountered in
the past may not protect you from new influenza strains that can be very
different viruses from what you had before.
Risk factors of Influenza
Factors that may increase your risk of
developing the flu or its complications include:
- Age. Seasonal
influenza tends to target children 6 months to 5 years old, and adults 65
years old or older.
- Living or working conditions. People
who live or work in facilities with many other residents, such as nursing
homes or military barracks, are more likely to develop the flu. People who
are staying in the hospital also are at higher risk.
- Weakened immune system. Cancer
treatments, anti-rejection drugs, long-term use of steroids, organ
transplants, blood cancer, or HIV/AIDS can weaken the immune
system. This can make it easier to catch the flu and may also increase the
risk of developing complications.
- Chronic illnesses. Chronic
conditions, including lung diseases such as asthma, diabetes, heart
disease, nervous system diseases, metabolic disorders, airway
abnormality, and kidney, liver, or blood disease, may increase the risk of
influenza complications.
- Race. Native
American people may have an increased risk of influenza complications.
- Aspirin use under age 19. People
who are younger than 19 years of age and receiving long-term aspirin
therapy are at risk of developing Reye's syndrome if infected with
influenza.
- Pregnancy. Pregnant
women are more likely to develop influenza complications, particularly in
the second and third trimesters. Women are more likely to develop
influenza-related complications up to two weeks after delivering their
babies.
- Obesity. People
with a body mass index (BMI) of 40 or more have an increased risk of flu
complications.
Complications of Influenza
If you're young and healthy, the flu
usually isn't serious. Although you may feel miserable while you have it, the
flu usually goes away in a week or two with no lasting effects. But children
and adults at high risk may develop complications that may include:
- Pneumonia
- Bronchitis
- Asthma
flare-ups
- Heart
problems
- Ear
infections
- Acute
respiratory distress syndrome
Pneumonia is one of the most serious
complications. For older adults and people with a chronic illness, pneumonia
can be deadly.
Prevention of Influenza
The Centers for Disease Control and
Prevention (CDC) recommends annual flu vaccination for everyone 6 months or
older. The flu vaccine can reduce your risk of the flu and its severity and
lower the risk of having serious illness from the flu and needing to stay in
the hospital.
Flu vaccination is especially important
this season because the flu and coronavirus disease 2019 (COVID-19) cause
similar symptoms. Flu vaccination could reduce symptoms that might be confused
with those caused by COVID-19. Preventing the flu and reducing the
severity of flu illness and hospitalizations could also lessen the number of
people needing to stay in the hospital.
It may be possible to get
a COVID-19 vaccine at the same time as your flu vaccine.
This year's seasonal flu vaccine
provides protection from the four influenza viruses that are expected to be the
most common during the year's flu season. This year, the vaccine will be
available as an injection and as a nasal spray.
The nasal spray isn't recommended for
some groups, such as:
- Children
under 2
- Adults
50 and older
- Pregnant
women
- Children
between 2 and 17 years old who are taking aspirin or a
salicylate-containing medication
- People
with weakened immune systems
- Kids 2
to 4 years old who have had asthma or wheezing in the past 12 months
You can still get a flu vaccine if you have an egg allergy.
Controlling the spread of infection
The influenza vaccine isn't 100%
effective, so it's also important to take several measures to reduce the spread
of infection, including:
- Wash your hands. Washing
your hands often with soap and water for at least 20 seconds is an
effective way to prevent many common infections. Or use alcohol-based hand
sanitizers if soap and water aren't available.
- Avoid touching your face. Avoid
touching your eyes, nose, and mouth.
- Cover your coughs and sneezes. Cough
or sneeze into a tissue or your elbow. Then wash your hands.
- Clean surfaces. Regularly
clean often-touched surfaces to prevent the spread of infection from touching
a surface with the virus on it and then your face.
- Avoid crowds. The flu
spreads easily wherever people gather — in child care centers, schools,
office buildings, auditoriums, and public transportation. By avoiding
crowds during peak flu season, you reduce your chances of infection.
Also, avoid anyone who is sick. And if
you're sick, stay home for at least 24 hours after your fever is gone so that
you lessen your chance of infecting others.
Both COVID-19 and the flu may
be spreading at the same time. Your local health department and
the CDC may suggest other precautions to reduce your risk
of COVID-19 or the flu if you haven't been fully vaccinated. For
example, you may need to practice social distancing (physical distancing) and
stay at least 6 feet (2 meters) from others outside your household. You may
also need to wear a cloth face mask when indoors with people outside your
home and when outdoors in crowded areas. If you're fully vaccinated and
are in an area with a high number of new COVID-19 cases in the last
week, the CDC also recommends wearing a mask indoors in public and
outdoors in crowded areas or when you're in close contact with unvaccinated
people.
Diagnosis of Influenza
Your doctor will conduct a physical
exam, look for signs and symptoms of influenza, and possibly order a test that
detects influenza viruses.
During times when influenza is
widespread, you may not need to be tested for influenza. Your doctor may
diagnose you based on your signs and symptoms.
In some cases, your doctor may suggest
that you be tested for influenza. He or she may use various tests to diagnose
influenza. Polymerase chain reaction (PCR) testing is becoming more common in
many hospitals and labs. This test may be done while you're in your doctor's
office or in the hospital. PCR testing is more sensitive than other
tests and may be able to identify the influenza strain.
It's possible to have a test to diagnose both influenza and COVID-19. You may have both COVID-19 and influenza at the same time.
Treatment of Influenza
Usually, you'll need nothing more than
rest and plenty of fluids to treat the flu. But if you have a severe infection
or are at higher risk of complications, your doctor may prescribe an antiviral
drug to treat the flu. These drugs can include oseltamivir (Tamiflu), zanamivir
(Relenza), peramivir (Rapivab), or baloxavir (Xofluza). These drugs may shorten
your illness by a day or so and help prevent serious complications.
Oseltamivir is an oral medication.
Zanamivir is inhaled through a device similar to an asthma inhaler and
shouldn't be used by anyone with certain chronic respiratory problems, such as
asthma and lung disease.
Antiviral medication side effects may
include nausea and vomiting. These side effects may be lessened if the drug is
taken with food.
Most circulating strains of influenza
have become resistant to amantadine and rimantadine (Flumadine), which are
older antiviral drugs that are no longer recommended.
Lifestyle and home remedies
If you do come down with the flu, these
measures may help ease your symptoms:
- Drink plenty of liquids. Choose
water, juice, and warm soups to prevent dehydration.
- Rest. Get
more sleep to help your immune system fight infection. You may need to
change your activity level, depending on your symptoms.
- Consider pain relievers. Use an
over-the-counter pain reliever, such as acetaminophen (Tylenol, others) or
ibuprofen (Advil, Motrin IB, others), to combat the achiness associated
with influenza. Children and teens recovering from flu-like symptoms
should never take aspirin because of the risk of Reye's syndrome, a rare
but potentially fatal condition.
To help control the spread of influenza in your community, stay home and keep sick children home until the fever has been gone for 24 hours. Avoid being around other people until you're feeling better unless you're getting medical care. If you do need to leave your home and get medical care, wear a face mask. Wash your hands often.
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