All You Need To Know About Influenza (The Flu)

• Are Influenza and the Flu the Same Thing?
• How is Influenza Transmitted? 
• What are the Symptoms of Influenza?
• How is Influenza Diagnosed?
• What should I do if I get the flu?
• When should I consult my doctor?
• What Else Could I Have Besides Influenza?
• How is the Flu Treated?
• Persons at High Risk for Flu Complications
• How Do I Prevent my Newborn from Catching the Flu?
• How Can I Prevent Catching and Spreading the Flu?
• Measures to Prevent Respiratory Viral Infections
• How Effective is the Flu Vaccine?
• Can I Still Get the Flu After Being Vaccinated?
• Will the Flu Vaccine Make me Sick?
• What Are Some Side Effects of the Influenza Vaccine?
• How Many People Die From the Flu?
• What is the Spanish Flu?

Are Influenza and the Flu the Same Thing?

Yes, influenza, also known as “the flu,” has primarily respiratory symptoms. So, that means that they involve your breathing tract, from your nose down to your lungs. Sometimes, people will say they have “the stomach flu” when they have a gastrointestinal virus, with mainly vomiting and diarrhea symptoms. However, while influenza can sometimes cause stomach-related symptoms, they are not the main symptoms. But the influenza virus is not related to the gastrointestinal viruses. “Stomach flu” is a popular common term. But medically, “flu” is only used to describe influenza-related illness. In this article, the flu and influenza are used interchangeably.

How is Influenza Transmitted?

In most cases, people who develop the flu do so 2-4 days after being exposed to someone with influenza. People with influenza are contagious, starting up to 2 days before they are sick. But most stop being contagious a week after their symptoms start.

Influenza spreads primarily via contact with respiratory secretions, which means nasal secretions, saliva, and sputum (also called phlegm). When you cough or sneeze, the virus is sprayed into the air and breathed in by others. And the virus in the air can land on surfaces that you later touch. Also, someone with influenza could have the virus on their hand from blowing their nose or coughing, and then touch a doorknob or handle that you then touch. So, if you rub your eye or nose or fail to wash your hands before eating, you could infect yourself with the virus. You could also catch influenza by kissing an infected person on the mouth.

Flu Transmission:

• First, persons with flu are contagious for two days before they start showing symptoms.
• Next, nasal secretions, saliva, and sputum are the primary sources of transmission.
• Finally, transmission through kissing, breathing in contaminated air, touching contaminated surfaces, and then eating or touching your face.

What are the Symptoms of Influenza?

Influenza tends to start abruptly, some people describing it as “like being hit by a brick wall.” Sometimes you develop fever, body aches, and extreme fatigue. And other symptoms that usually develop include sore throat, cough, and runny nose. Like most illnesses, there is a range of symptoms. Usually, fevers tend to be 100.5^oF (38^oC) or higher. Older adults may have atypical and vague symptoms such as loss of appetite, a general feeling of not being well, weakness, or dizziness. But children are more prone to having vomiting or diarrhea.

Influenza tends to last 2-5 days but can last up to a week. For instance, fatigue or weakness can sometimes last for weeks after influenza. However, you should see a doctor if your symptoms last for more than a week to be sure there isn’t a more serious illness. So, severe or prolonged symptoms could mean you have developed a complication of influenza.

Symptoms can vary from one person to another but usually include:

• Fever (temperature higher than 100ºF, or 37.8ºC) lasting 2-7 days.
• Extreme fatigue.
• Headache.
• Muscle aches.
• Cough.
• Runny nose. 
• Sore throat. 

How is Influenza Diagnosed?

There are two ways to diagnose influenza-based on symptoms or based on tests. First, most people are diagnosed based on symptoms. This is called a “clinical diagnosis.” Second, you may also have a swab done for a rapid influenza test. This involves placing a tiny swab through your nose until it reaches the back of your throat.

There are multiple types of influenza tests available. Sometimes the tests available in doctors’ offices are prone to a significant number of false negative results. So, if you have all the classic flu symptoms, you will be diagnosed and treated for the flu, even if you test negative. And in cases where the symptoms are convincing for the flu, a test is not necessary. But flu tests are helpful when the diagnosis is not clear or if you are at high risk for flu complications. Still, your doctor may do a flu swab if you are at high risk to minimize the chance of missing an atypical flu case even if you are symptoms are not likely to flu.

What should I do if I get the flu?

• To start, you should rest at home, drink plenty of fluids, and use acetaminophen (Tylenol) for fever and muscle aches.
• Yet, most people get better on their own, with fevers resolving in 2-5 days and muscle aches and tiredness resolving in up to two weeks.

When should I consult my doctor?

• If you are at high risk for complications.
• Within the first 48 hours of symptoms to determine if you need anti-viral medicines, especially if you are in a high-risk group.
• If your symptoms last longer than a week. 
• Call your healthcare provider right away if you have:
  • Trouble breathing or shortness of breath.
  • Pain or pressure in your chest.
  • Dizziness or confusion.
  • Trouble drinking enough fluids.
  • A fever and you have a high risk condition. 
  • A cough that lasts more than ten days.
  • Chest pain when you cough.
  • Coughing up blood.
  • Vomiting.

What Else Could I Have Besides Influenza?

Other things can cause the same symptoms of influenza. Usually, the more common possibilities are listed below.

1. Common Cold. The common cold is a seasonal infection also caused by a respiratory virus, just like the flu. Yet, multiple different viruses can cause the common cold. But, one of the main differences between the flu and the common cold is that a fever is almost always absent or low-grade with a cold.
2. Seasonal Allergies. Sometimes, seasonal allergies are your body’s allergic inflammatory response to something within the environment. And, it is not an infection. Rather, it is an inflammation. Occasionally, seasonal allergies can be confused with respiratory viruses. However, unlike the flu, there are no fevers or body aches with allergies. Still, sneezing and itchy eyes are more common with allergies than with the flu. Also, most allergies are recurrent, occurring at the same time yearly. But, this is not the case with the flu.
3. Sinus Infection (Sinusitis). There is a major overlap with sinus infection symptoms and other respiratory infections. But, there are a few notable differences. Headache location is different for flu versus sinusitis. On one hand, sinus infection headaches are more facial, located in your forehead and cheekbone areas. On the other hand, flu headaches are more on the top and back of your head. In most cases, people do not get a fever with a sinus infection. But, if you do get a fever with sinusitis, it is usually low-grade, 100.4 F or less. Also, with sinusitis, fevers are more likely to occur later in the illness, after several days. Sometimes nasal congestion is common with sinusitis. But body aches are not. Oftentimes, nasal drainage becomes thick and cloudy, yellow, or green. And sinus infections can develop as a complication of a cold or flu. For example, if, after a week of having the flu, your symptoms resolve, but you continue to have worsening sinus pressure and drainage, you might have a sinus infection.
4. Pneumonia. Pneumonia is an infection in the lungs that can be caused by a virus or bacteria. Common symptoms include cough and fever, similar to influenza. Also, pneumonia symptoms can occur suddenly, just like the flu. For instance, chest pain, shortness of breath, and sputum production are more common in pneumonia. Further, nausea, vomiting, and diarrhea are also common. Sometimes pneumonia can be a complication of influenza. Meaning that if you have the flu, this increases your chance of developing pneumonia. So, if you develop shortness of breath, fever, chest pain, or worsening cough or sputum production, you may have developed pneumonia in addition to influenza. You should see a doctor right away.
5. Bronchitis. Bronchitis is an inflammation of the lining in your lower lungs. Cough is the predominant symptom of bronchitis, and it can last up to 3 weeks. Sputum is often present and can be any color. Sometimes bronchitis can occur as a complication of a cold or flu. As your cold or flu symptoms resolve, your cough persists or may even worsen. With bronchitis, mild shortness of breath or wheezing can occur. If you have prolonged coughing, this can create a strain on your chest wall muscles. Fever is rare. People with lung problems such as asthma or chronic obstructive lung disease (COPD) are more prone to developing bronchitis.
6. COVID-19. Influenza is very difficult to differentiate from COVID-19 without testing. Fever tends to occur a little later with COVID but not always. A diminished sense of taste or smell can be seen with COVID but not often with influenza. At this time, there is no way to tell accurately just based on symptoms, whether you have the flu or COVID. Talk to your doctor about whether you should get a COVID test if you have flu symptoms.

Symptom Tracker

Symptom	Influenza	Common Cold	Allergies	Sinus Infection	Pneumonia	Bronchitis	COVID-19 (SARS-2 Coronovirus)	Symptom
Fever	xxx	None or low grade	No	x	xxx	Rare	xxx	Fever
Headache	x	x	x	xxx Facial HA- forehead, cheekbone	x	x	xxx	Headache
Body Ache	xxx	x	No	None or rare	x	None or rare	xxx	Body Ache
Cough	xxx	x	x	x	xxx	xxx	xxx	Cough
Difficulty Breathing	xxx	x	Possible Wheezing	rare	xxx	x	xxx	Difficulty Breathing
Sore Throat	x	rare	x	x	rare	rare	x	Sore Throat
Nasal Congestion	x	x	x	xxx	x	x	x	Nasal Congestion
Sneezing	x	x	xxx	x	x	x	rare	Sneezing
Itchy Eyes	No/rare	No/rare	xxx					Itchy Eyes
Seasonal Occurrence	x	x	xxx	no	no	no	no	Seasonal Occurrence
Nausea Vomiting Diarrhea	x	rare	rare	rare	x	rare	no	Nausea Vomiting Diarrhea
New Loss of taste or smell	no	no	no	no	no	no	xxx	New Loss of taste or smell

Legend: x- possible symptom, xxx= predominant symptom

How is the Flu Treated?

In most cases, you will get over the flu by your immune system fighting it off. Therefore, supporting your immune system is very important. But there are no vitamins or supplements that are proven to help boost your immune system.

However, two of the most important ways to support your immune system are through rest and hydration. Sometimes, fatigue is a sign that your immune system is working hard to fight the flu virus. So, you must listen to your body and rest. Usually, taking the time to rest and recover will help you feel better sooner than if you try to “push through it.”

When you are sick, you often need more fluids than average, especially if you have a fever. In this case, you must watch for dehydration symptoms. To explain, they include dry mouth, lack of tears, lightheadedness, decreased urine, or feeling tired. So if you develop any of these symptoms, you need to drink more. And if you cannot drink more, or if your symptoms persist or worsen, you need to see a doctor right away.

Fortunately, there are anti-viral medications that help your body fight the influenza virus. Oftentimes, doctors prescribe Tamiflu^TM (Oseltamivir) and Xofluza^TM (Baloxavir Marboxil). But there are others that can be used less frequently in special situations or hospitalization. No, these medications do not cure the flu. But they help your immune system fight it. However, anti-viral medicines work the best if they are started within the first 48 hours of your illness. So, call your doctor within the first 48 hours of your developing symptoms to find out if you need anti-viral treatment. Usually, doctors recommend anti-viral medications for anyone at high risk of flu complications. To specify, there is a list of the high-risk categories below.

There are medications used for the flu called antivirals:

• Tamiflu^TM (Oseltamivir) and Zanamivir^TM (Relenza) (Prevent)
• Rapivab^TM (Peramivir Injection) and Xofluza^TM (Baloxavir Marboxil) (Treat)
• Not everyone who gets the flu needs medication. Instead, your doctor will decide based on several factors.
• If you are severely ill and/or at risk for having complications from the flu, you will need treatment with an antiviral.
• If you are not at risk for complications from the flu and your symptoms began within the past 48 hours, your doctor may prescribe an antiviral. In fact, antivirals work best when taken within 48 hours of the start of symptoms.
• Further, treatment with antivirals lowers the severity of symptoms and shortens the duration of the flu by one day.
• But if you are a healthy person with mild symptoms present for more than 48 hours, you will not be prescribed antiviral medication. 
• Antibiotics are not used to treat the flu.

If you have the flu, you have the option of taking an anti-viral medicine, even if you are at low risk for complications. To make the best decision about flu medications, your doctor will consider the medications’ potential risks and benefits. On one hand, common side effects of TamifluTM (Oseltamivir) include nausea and vomiting. On the other hand, XofluzaTM (Baloxavir Marboxil) may cause diarrhea and allergic reactions. TamifluTM (Oseltamivir) has been around for longer. So, it is available as a generic, making it less expensive and the preferred drug for severe cases of the flu.

The benefits are that anti-viral medicines decrease your risk of flu complications. They also help you get better faster and reduce the risk of transmission to others. It is important that you follow your doctor’s recommendations on when and how to take anti-viral medicines. Improper use of the drug can not only hurt you. But it can also cause the virus to become resistant, making it much harder to treat you and others in case of future infection.

In brief, if you have had close exposure to someone with the flu and you are at high-risk for flu complications, you should talk to your doctor about whether you should take an anti-viral to help prevent you from getting the flu.

Persons at High Risk for Flu Complications

Children under 5. The younger the child, the higher the risk.	Children taking aspirin daily
Women who gave birth within the last 2 weeks	Pregnant Women
Age 65 or older	Nursing home residents
Severe obesity, BMI of 40 or higher	Diabetics
Kidney problems	Liver problems
Sickle cell anemia	Native Americans
Inherited metabolic disorders	Heart disease including coronary artery disease, congestive heart disease, and congenital heart disease.
Chronic lung conditions including asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis	Neurological disorders including cerebral palsy, epilepsy, stroke, muscular dystrophy, spinal cord injury, Parkinson’s disease, moderate-to-severe developmental delay.
Immune system compromise due to illness or medications such as HIV, auto-immune disorder, transplant patients, steroids.	Active cancer diagnosis or treatment

How Do I Prevent my Newborn from Catching the Flu?

Unfortunately, babies under age six months are at very high risk for serious complications from the flu. And their immune system is not mature enough to fight the influenza virus. But, they are also too young to get the vaccine. Still, prevention of infection in this age group is critical. In fact, methods for prevention include all the previously discussed methods. But the mom should also be vaccinated while pregnant, along with all caregivers.

Flu Prevention in Newborns:

• Vaccination in Pregnancy.
• Vaccination for all caregivers.

How Can I Prevent Catching and Spreading the Flu?

The old saying “an ounce of prevention is worth a pound of cure” is very true with the flu. On average, 36,000 Americans die yearly from the flu, with many of these deaths being preventable.

Measures to Prevent Respiratory Viral Infections

• For one thing, wash your hands frequently. And wash them well with soap and water for at least 20 seconds.
• But if you do not have access to soap and water, use an alcohol-based hand sanitizer for at least 20 seconds to clean your hands.
• Also, cover your coughs and sneezes with the inside of your elbow.
• And throw away your tissue right after blowing your nose. Further, keep them off surfaces.
• Plus, stay home from work or school if you are sick.
• Finally, get a flu vaccine annually.

Getting a flu vaccine is also very important in preventing the flu. In fact, both an injection (flu shot) or a nasal spray are the current available options for flu vaccines. And everyone over the age of 6 months, regardless of their risk category, is recommended to get a yearly flu shot. But the exception is if your doctor says you cannot safely get a flu vaccine for health reasons. However, these exceptions are few in number.

 

• Newborns less than 6 months of age
• History of a severe allergic reaction to a previous influenza vaccine or to any component of the vaccine.

In the past, persons with egg allergy were unable to receive a flu vaccine. But now there are vaccines available with no egg component. In most cases, people who do not have a severe egg allergy can safely receive any flu vaccine. Still, let your doctor know if you have had a previous egg allergy before you get immunized so that you may get vaccinated safely. But the nasal spray flu vaccine, which is a weakened live virus vaccine, has some additional restrictions.

 

• History of a severe allergic reaction to a previous influenza vaccine or to any component of the vaccine.
• Children or adolescents who are taking aspirin or other salicylate-containing medication.
• Children age 2-4 years who have had asthma or wheezing.
• Immunocompromised individuals and close contacts or caregivers of immunocompromised individuals.
• Pregnant Women.
• Those taking influenza anti-viral medication within the last 48 hours.

 

• Asthma in persons age five or older.
• Persons at high risk for influenza complications.

 

• People with current serious illness or infection.
• Persons who developed Guillain-Barre syndrome within six weeks after a previous influenza vaccine.

Overall, a precaution for the influenza vaccine means that the vaccine may be given if you and your doctor feel the benefits outweighs the risks. And a vaccine exemption (contraindication) means that you should not take the vaccine.

How Effective is the Flu Vaccine?

No vaccine is 100% effective. And the flu vaccine is no different. In fact, the flu vaccine contains strains of different types of flu. There are strains of influenza A, influenza B, and H1N1. In short, H1N1 is a subtype of influenza A and is also known as the swine flu. However, these are just a few of the strains that are usually included in the flu vaccine. Rather the flu vaccine efficacy varies from year to year as the strains of the flu vary annually. And a flu vaccine from last year will not protect you this year. Finally, the effectiveness is highest in toddlers and children and decreases as you age. In 2018-2019, the effectivity of the flu vaccine ranged from 17% to 87%.

In general, the flu vaccine is not as effective in persons over age 65, a group at high risk of complication. There is a high dose flu vaccine specifically designed for persons over age 65, that is more effective for this group. Further, the center for disease control (CDC) recommends that persons caring for newborn babies, the elderly, or anyone in the high-risk group, receive a flu vaccine.

Can I Still Get the Flu After Being Vaccinated?

Because the flu vaccine is not 100% protective, you still have a risk of contracting the flu. So, if you happen to get the flu despite being vaccinated, there is still benefit. In fact, you are less likely to suffer severe illness and will recover faster than if you were unvaccinated.

Will the Flu Vaccine Make me Sick?

One of the biggest myths about the flu vaccine is that it gives you the flu. Most flu vaccines contain no live virus. Rather they contain either the dead virus or viral particles. But a dead virus or viral particle cannot cause an infection. Instead it causes your body to mount antibodies against the flu, which is what a vaccine is supposed to do. The nasal flu vaccine contains an attenuated live virus, which means the virus has been weakened. So, it can’t cause infection. Yet, the nasal flu vaccine is less commonly used than the injectable vaccine.

What are Some Side Effects of the Influenza Vaccine?

Usually, most side effects from the vaccine are symptoms of your immune system responding to the vaccine as it works on building immunity to the flu. In other words, what you are feeling is the vaccine doing what it is supposed to do. And you may develop a low-grade fever and body aches from the injectable flu vaccine. But, these side effects are usually mild and last 1-2 days. Usually, soreness, redness, and swelling at the site where the shot is given are common and usually go away in two days.

Still, keep in mind that it takes about two weeks for the flu shot to be effective. For this reason, you can catch the flu during this time. However, if you get a flu shot and have mild side effects for 1-2 days, you may be experiencing side effects of the vaccine. But, if your symptoms last longer than two days, it is more likely that you coincidentally contracted a respiratory virus around the time of your flu shot.

Sometimes, the nasal spray flu vaccine can cause a runny nose, nasal congestion, wheezing, headache, vomiting, muscle aches, fever, sore throat, and cough. Usually, these side effects are mild. And, they start soon after being vaccinated.

So, if you feel you are having anything other than a mild reaction to a flu vaccine, you should always call your doctor to be sure a serious condition does not exist.

How Many People Die From the Flu?

The flu mortality rate varies each year. But, according to the centers for disease control, in 2018, 11,164 people died from influenza in the U.S. As a result, this showed a death rate of 3.4 per 100,00. And, when combined with pneumonia, which can be a complication of influenza, the deaths jump to 59,120 or 18.1 per 100,000. So, the mortality in 2018 in the US was less than 1%.

What is the Spanish Flu?

Oftentimes, the Spanish Flu is the common name used to describe the influenza pandemic of 1918. In fact, the pandemic was caused by the H1N1 Influenza Type A virus. At the time, the mortality was high due to lack of vaccinations for prevention and lack of antibiotics to treat the bacterial infections that sometimes develop as a complication of the flu. And the influenza pandemic of 1918 killed 500 million people worldwide and 675,000 in the U.S. Unfortunately, the origin of the influenza pandemic was never determined.

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written by: myObMD writing team, November 13, 2020 | Editor: Dayna Smith, MD | Copyright: myObMD Media, LLC, 2021

Glossary:

• Antibodies – These are the molecules, or substances, that the immune system makes to fight illness.
• Attenuated – Weakened, usually as in a weakened virus used in a vaccine.
• Contraindication – A situation or condition where a medication should not be used as the risks likely outweigh the benefits.
• Gastrointestinal – This refers to your digestive tract and includes your mouth down to your stomach, intestines, and your rectum/anus.
• Guillain-Barre Syndrome – This is a rare autoimmune disorder involving your nerves. Usually, it starts with weakness and numbness/tingling in the arms and legs. But, it spreads. And it can paralyze your whole body. In most cases, people recover from Guillain Barre. Still, the cause is unknown. However, it usually starts after a viral infection. But it can also occur less often after a surgery. Or it may rarely happen after vaccinations.
• Immunocompromised – When the immune system is not fully functional due to a medical problem, as a result of medications, or with newborns and infants.
• Lethargy – Extreme fatigue, weakness, and/or sleepiness.
• Resistance – This is when a medication, such as an antibiotic or anti-viral medication, no longer works. Sometimes, the bacteria or virus, if exposed to the antibiotic or anti-viral medication, can eventually develop the ability to block the effect of those medications.
• Respiratory – This refers to anything involving your breathing tract, from your nose, down your throat, to your lungs.