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What are the signs and symptoms of the flu?

Flu Signs and Symptoms

Flu Symptoms

Influenza (also known as the flu) is a contagious respiratory illness caused by flu viruses. It can cause mild to severe illness, and at times can lead to death. The flu is different from a cold. The flu usually comes on suddenly. People who have the flu often feel some or all of these symptoms:

  • Fever* or feeling feverish/chills
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headaches
  • Fatigue (tiredness)
  • Some people may have vomiting and diarrhea, though this is more common in children than adults.

* It’s important to note that not everyone with flu will have a fever.

 

Flu vs Cold

Signs and SymptomsInfluenzaCold
Symptom onsetAbruptGradual
FeverUsual; lasts 3-4 daysRare
AchesUsual; often severeSlight
ChillsFairly commonUncommon
Fatigue, weaknessUsualSometimes
SneezingSometimesCommon
Stuffy noseSometimesCommon
Sore throatSometimesCommon
Chest discomfort, coughCommon; can be severeMild to moderate; hacking cough
HeadacheCommonRare

 

Flu Complications

Most people who get influenza will recover in several days to less than two weeks, but some people will develop complications as a result of the flu. A wide range of complications can be caused by influenza virus infection of the upper respiratory tract (nasal passages, throat) and lower respiratory tract (lungs). While anyone can get sick with flu and become severely ill, some people are more likely to experience severe flu illness. Young children, adults aged 65 years and older, pregnant women, and people with certain chronic medical conditions are among those groups of people who are at high risk of serious flu complications.

 

People at High Risk of Developing Flu–Related Complications

 

 

Many people do not know if they are at high risk for flu complications.

Most people who get the flu will have mild illness, will not need medical care or antiviral drugs, and will recover in less than two weeks. Some people, however, are more likely to get flu complications that can result in hospitalization and sometimes death. Pneumonia, bronchitis, sinus infections and ear infections are examples of flu-related complications. The flu also can make chronic health problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic congestive heart failure may experience a worsening of this condition triggered by flu. List below are the groups of people who are more likely to get serious flu-related complications if they get sick with influenza.

 

People at High Risk for Developing Flu-Related Complications

  • Children younger than 5, but especially children younger than 2 years old
  • Adults 65 years of age and older
  • Pregnant women (and women up to two weeks postpartum)
  • Residents of nursing homes and other long-term care facilities
  • Also, American Indians and Alaskan Natives eem to be at higher risk of flu complications

People who have medical conditions including:

  • Asthma
  • Neurological and neurodevelopmental conditions [including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy (seizure disorders), stroke, intellectual disability (mental retardation), moderate to severe developmental delay, muscular dystrophy, or spinal cord injury].
  • Chronic lung disease (such as chronic obstructive pulmonary disease [COPD] and cystic fibrosis)
  • Heart disease (such as congenital heart disease, congestive heart failure and coronary artery disease)
  • Blood disorders (such as sickle cell disease)
  • Endocrine disorders (such as diabetes mellitus)
  • Kidney disorders
  • Liver disorders
  • Metabolic disorders (such as inherited metabolic disorders and mitochondrial disorders)
  • Weakened immune system due to disease or medication (such as people with HIV or AIDS, or cancer, or those on chronic steroids)
  • People younger than 19 years of age who are receiving long-term aspirin therapy
  • People with extreme obesity (body mass index [BMI] of 40 or more)

For example, people with chronic lung disease are at higher risk of developing severe pneumonia.

Sinus and ear infections are examples of moderate complications from flu, while pneumonia is a serious flu complication that can result from either influenza virus infection alone or from co-infection of flu virus and bacteria. Other possible serious complications triggered by flu can include inflammation of the heart (myocarditis), brain (encephalitis) or muscle (myositis, rhabdomyolysis) tissues, and multi-organ failure (for example, respiratory and kidney failure). Flu virus infection of the respiratory tract can trigger an extreme inflammatory response in the body and can lead to sepsis, the body’s life-threatening response to infection. Flu also can make chronic medical problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic heart disease may experience a worsening of this condition triggered by flu.

 

Signs and Symptoms

 

  • Being unable to eat
  • Has trouble breathing
  • Has no tears when crying
  • Significantly fewer wet diapers than normal

In addition to the signs above, get medical help right away for any infant who has any of these signs:

In children:

  • Fast breathing or trouble breathing
  • Bluish skin color
  • Not drinking enough fluids
  • Not waking up or not interacting
  • Being so irritable that the child does not want to be held
  • Flu-like symptoms improve but then return with fever and worse cough
  • Fever with a rash

In adults:

  • Difficulty breathing or shortness of breath
  • Pain or pressure in the chest or abdomen
  • Sudden dizziness
  • Confusion
  • Severe or persistent vomiting
  • Flu-like symptoms that improve but then return with fever and worse cough

 

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