Influenza (flu) - Symptoms, diagnosis, treatment, prevention

Influenza is an infection of a number of viruses attacking the respiratory system. Influenza is commonly called flu. Between 5% and 20% of people in the U.S. get the flu each year.

Flu viruses are most common during the fall and winter. The exact timing and duration of flu seasons can vary, but influenza activity often begins to increase in October. Most of the time flu activity peaks between December and February, although activity can last as late as May.



The symptoms of flu is similar to those of a cold, cold is mild yet flu can be serious.

Cold symptoms include:

  • Fever up to 102°F
  • Runny or stuffy nose
  • Green or yellow nasal discharge
  • Sore throat
  • Cough
  • Sneezing
  • Feeling tired
  • Muscle aches
  • Headache
  • Watery eyes
  • Symptoms develop slowly
  • Symptoms are mild

Flu symptoms include:

  • Fever over 102°F
  • Stuffy nose
  • Nausea
  • Chills and sweats
  • Feeling tired
  • Muscle aches, especially in back, legs, and arms
  • Cough
  • Headache
  • Poor appetite
  • Symptoms appear suddenly
  • Symptoms are more intense

For a common flu, what you need is bed rest and hydration. But flu can be severe, if you have these symptoms you need to get medical help.

Children serious symptoms

  • High fever (above 103°F)
  • Fever that lasts for more than 3 days
  • Trouble breathing, fast breathing, or wheezing
  • Bluish skin color
  • Earache or ear drainage
  • Difficulty waking up
  • Irritability
  • Seizures
  • Symptoms that improve and then return with a fever or worse cough
  • Worsening of chronic medical conditions (such as diabetes or heart disease)
  • Vomiting or stomach pain

Adults serious symptoms

  • A high, prolonged fever (above 102°F) with fatigue and body aches
  • Symptoms that last longer than 10 days or get worse
  • Trouble breathing or shortness of breath
  • Chest pain or pressure
  • Fainting or feeling like you are going to faint
  • Confusion or disorientation
  • Severe or persistent vomiting
  • Severe sinus pain in your face or forehead
  • Swollen gland in the neck or jaw



Influenza virus is the cause to flu. There are four types of influenza viruses: A, B, C and D. Human influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. Influenza type C infections generally cause a mild respiratory illness and are not thought to cause epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.

Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N). There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes. (H1 through H18 and N1 through N11 respectively.)

Influenza A viruses can be further broken down into different strains. Current subtypes of influenza A viruses found in people are influenza A (H1N1) and influenza A (H3N2) viruses.

Influenza B viruses are can be further broken down into lineages and strains. Currently circulating influenza B viruses belong to one of two lineages: B/Yamagata and B/Victoria.

Influenza viruses are constantly changing. When the virus changes into an antigenically different type, the body immune system can’t recognize the virus and people get infected. That’s why people at higher risk need to get the flu vaccination every year.


Who are at higher risk

People at higher risk of developing flu complications include:

  • Young children under age 5, and especially those under 2 years
  • Adults older than age 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, liver disease and diabetes
  • People who are very obese, with a body mass index (BMI) of 40 or higher



Your doctor will conduct a physical exam. A number of flu tests are available. The most common are called “rapid influenza diagnostic tests (RIDTs). The rapid tests can provide results within approximately 10-15 minutes, but not always accurate, false negatives exist. Therefore, your doctor may diagnose based on your symptoms despite of the negative test result.



Although most people need only rests and fluids to recover from a flu, some people may need antiviral treatment.

People at high risk of flu complications include young children, adults 65 years of age and older, pregnant women, and people with certain medical conditions such as asthma, diabetes and heart disease should contact their doctor right after the flu symptoms show.

Antiviral treatment can relieve symptoms and shorten the time you’re sick by 1 to 2 days. Oseltamivir (Tamiflu) and zanamivir (Relenza) are the common antiviral medication for flu.

Oseltamivir is an oral medication. Zanamivir is inhaled through a device similar to an asthma inhaler. Side effects may include nausea and vomiting. These side effects may be lessened if the drug is taken with food. Oseltamivir has also been associated with delirium and self-harm behaviors in teenagers.

OTC drugs can relieve the flu symptoms.

If your child is having flu, this article will provide you with information.

Young children in flu – what to do


For healthy adults and children older than 5, a few actions can lower your risk of flu, including:

  1. washing hands thorough and frequent with soap, use alcohol-based hand sanitizers if soap isn’t available
  2. avoid crowds
  3. keep hydrated and take fresh vegetables and fruits everyday

The best way of prevention is taking the annual vaccination. Each year’s seasonal flu vaccine contains protection from the three or four influenza viruses that are expected to be the most common during that year’s flu season. The vaccine is now available as an injection and as a nasal spray.

If you’re taking care of a person with flu, the best way of prevention is still getting the vaccine. If you didn’t get a vaccine in time, protect yourself by wearing a mask and washing your hands frequently.

According to the Centers for Disease Control(CDC), the flu is most contagious five to seven days after flu symptoms develop. The flu can even be contagious one day before any flu symptoms develop.


Home care

Take zinc supplement: Zinc taken orally (by mouth) may help to treat colds, but it can cause side effects and interact with medicines. A 2015 analysis of clinical trials found that oral zinc helps to reduce the length of colds when taken within 24 hours after symptoms start. Intranasal zinc has been linked to a severe side effect (irreversible loss of the sense of smell) and should not be used.

Vitamin C does not prevent colds and only slightly reduces their length and severity. A 2013 review of scientific literature found that taking vitamin C regularly did not reduce the likelihood of getting a cold but was linked to small improvements in cold symptoms. In studies in which people took vitamin C only after they got a cold, vitamin C did not improve their symptoms.

Echinacea:  Echinacea is an herbal supplement that’s been used to treat or prevent colds for centuries. Echinacea products vary widely, containing different species, parts, and preparations of the echinacea plant.

Take probiotic supplements: probiotic supplements may help to prevent colds. Probiotics are a type of “good bacteria,” similar to the microorganisms found in the body, and may be beneficial to health. Probiotics are available as dietary supplements and yogurts, as well as other products such as suppositories and creams. A 2015 analysis of research indicated that probiotics might help to prevent upper respiratory tract infections.


Related articles:

  1. Researches Confirm Flu Raises Heart Attack Risks
  2. Tips in flu prevention
  3. Take 3 Actions to Fight the Flu
  4. Flu Season Getting Worse – Protect Children
  5. How to Enhance Immunity
  6. Influenza test






* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.