The flu is a respiratory (i.e., nose, throat, and lung) infection that can be caused by a variety of influenza viruses. Many people use the word “flu” when they actually have a cold. Although the common cold is also caused by viruses, the flu and common cold differ in several ways.
In North America, the flu almost always strikes between November and April. Up to 25% of the population may be infected in an average year. Stronger epidemics (i.e., when the flu occurs in more people than expected in a given area or season) come every 2 or 3 years, infecting twice as many people as during an “regular” year.
Most people who get the flu will recover within 1 to 2 weeks, but some people are at risk of developing complications such as pneumonia. On average, about 4,000 to 8,000 people in Canada die each year from complications of influenza, and about 20,000 people with the flu are hospitalized. Most of these people have other medical conditions, are seniors, or are very young children.
Influenza is contagious, which means it can be spread easily from person to person. Viruses that cause influenza spread from person to person mainly by droplets of respiratory fluids sent through the air when someone infected with the virus coughs or sneezes. Other people inhale the airborne virus and can become infected.
In some cases, the flu can be spread when someone touches a surface (e.g., doorknobs, countertops, telephones) that has the virus on it and then touches his or her nose, mouth, or eyes. The flu is most easily spread in crowded places such as schools and offices.
The flu takes 1 to 4 days to incubate in humans, but infected people become contagious before symptoms appear, often just the day after the virus enters the body. Adults remain infectious (i.e., they can spread the virus to others) for about 6 days, and children remain infectious for up to 10 days.
Initial flu symptoms include headaches, chills, and a cough. Symptoms such as fever, loss of appetite, and muscle aches soon follow. Other symptoms such as nausea, vomiting, and diarrhea are rare in adults but more common in children.
Since many people think they have the flu when it’s actually a bad cold, here’s a quick guide to help you tell the difference:
|Fever||uncommon||usually present, high (38°C to 41°C or 102°F to 104°F); lasts 3 to 4 days|
|aches and pains||slight||common and often severe|
|fatigue and weakness||mild||significant; can last 2 to 3 weeks|
|extreme exhaustion||never||very common at the start|
|chest discomfort and cough||mild to moderate, hacking cough||common; often severe with painful cough|
For most people, the flu lasts 1 or 2 weeks, but it can last for up to 1 month. The main complications are secondary bacterial infections of the sinuses or lungs (pneumonia). Symptoms include fever; chills; and yellow, green, or brown sputum (nasal discharge). Children are prone to ear infections like otitis media.
People in nursing homes are at a higher risk of complications from flu because they may have weak immune systems and often have other medical problems. People with asthma, chronic obstructive pulmonary disease, or congestive heart failure are also at a higher risk of developing bacterial infections like pneumonia.
In American studies, influenza hospitalization rates for children under 5 years of age were second only to the hospitalization rate in people over 65 years of age. School-aged children have the highest infection rates both during and between epidemics, and they are likely to be infected early in the season. Households with school-aged children have infection rates 30% above the average rate.
Since the symptoms of an influenza infection are very different from the common cold, the diagnosis can be made fairly quickly. Your doctor will be able to tell that you have the flu if you have at least some or most of these symptoms:
- aches and pains everywhere, especially in the back and legs
- bad headache
- burning sensation in the chest
- dry cough at first, then bringing up sputum
- high fever
- nausea and possible vomiting
- sore throat
- runny or stuffy nose
- extreme tiredness
If there is any doubt, your doctor can make sure that it’s the flu by taking a throat swab and testing it for the virus. This is rarely needed.
The normal treatment for flu is rest and plenty of liquids. Treatment also includes ways to prevent spreading the flu virus, such as proper hand washing, keeping common surfaces clean, and coughing or sneezing into your arm or sleeve.
Medications for specific symptoms can help. Cough suppressants can be used for cough. Acetylsalicylic acid* (ASA), ibuprofen, or acetaminophen can be used to treat symptoms of the flu, such as aches and fever. Children and teenagers with flu shouldn’t take ASA or other salicylates (medications related to ASA, such as salsalate or magnesium salicylate). The combination of influenza and ASA is linked to Reye’s syndrome, a rare but serious condition affecting the brain and liver. Many over-the-counter cold medications contain ASA or other salicylates. Ask your doctor or pharmacist about this.
Antibiotics are not effective against viral infections like flu and the cold, but they are prescribed for complications such as bacterial infections.
Antiviral medications are sometimes used to treat the flu. These medications can help shorten the duration of the flu and reduce symptoms if they are taken within 2 days of the start of symptoms. Antiviral medications are also recommended to prevent flu infection for some people. Antivirals can be used to prevent flu in children and adults after they come into close contact with a person who has the flu, such as flu-infected people who live in the same household. Generally, this is not recommended for most people; however, antivirals may be recommended for people at risk for flu complications. In these situations, antiviral medications should be started as soon as possible after becoming exposed to the person with the flu. Your doctor can decide whether you should start antiviral medications.
Amantadine is an antiviral but is usually not recommended for influenza A treatment because many of these viruses are resistant to it. However, if tests show the virus to be sensitive to amantadine, it can shorten the duration of symptoms if taken within 24 to 48 hours of symptoms appearing. It can also be used to prevent type A flu in certain circumstances. It carries some risk of side effects, including insomnia and confusion. Amantadine does not work against type B viruses.
Zanamivir and oseltamivir are antiviral medications that can be used to treat and prevent influenza A. They prevent newly formed viruses from escaping the infected cells that produced them. This limits further spread of the virus in the body. Zanamivir is an inhaled spray, whereas oseltamivir is a pill. Taken within 24 to 48 hours after the onset of illness, these medications reduce the duration of symptoms by an average of 1 to 3 days.
Flu antibodies can prevent the flu. The only ways to generate antibodies are to be infected or to get vaccinated. Because the flu viruses can change from year to year, vaccination needs to be repeated every year.
Each spring, a worldwide network of physicians and testing labs decide which flu strains are likely to cause trouble and design that year’s vaccine accordingly. The vaccine gives resistance to the type B strain and the two type A strains that are expected to predominate in the coming flu season.
The vaccine is over 80% effective in preventing flu in healthy adults, which means there is still a chance that you can get the flu – although your symptoms may be milder. The flu vaccine is given to anyone classified as the high risk for flu complications, and for people who are caregivers, health workers, and anyone who wants to avoid the flu. The flu vaccine is free in Ontario, and universal vaccination is encouraged.
High-risk groups for flu complications include:
- anyone aged 65 years or older
- young children under 5 years old (especially if they are less than 2 years old)
- people with underlying medical conditions, including people with:
- asthma and other chronic lung diseases (e.g., chronic obstructive pulmonary disease [COPD], cystic fibrosis)
- heart disease (e.g., coronary artery disease, congestive heart failure, congenital heart disease)
- chronic kidney or liver disease
- a weakened immune system (immunocompromised), which can be caused by:
- HIV/AIDS, an infection that attacks the immune system
- medications for certain conditions, such as:
- organ transplants: steroids, medications that suppress the immune system to prevent it from rejecting the organ (e.g., cyclosporine, tacrolimus, mycophenolate mofetil)
- cancer: chemotherapy
- certain types of arthritis, such as rheumatoid arthritis: steroids, biologics (medications that modify the response of the immune system, such as adalimumab or infliximab), medications that suppress the immune system to prevent it from attacking the body (e.g., methotrexate, azathioprine)
- Crohn’s disease: steroids, biologics (see above), or medications to suppress the immune system
- blood disorders (e.g., anemia, sickle cell anemia)
- neurologic and neurodevelopmental disorders that affect their ability to swallow and breathe
- morbid obesity (BMI of 40 or higher)
- residents of nursing homes or other chronic care facilities, regardless of age
- children receiving long-term ASA therapy
- pregnant women (especially if they are in their second or third trimester) and women who were recently pregnant (within the last 6 weeks)
- Aboriginal peoples
People who should not receive a flu shot include children less than 6 months of age and people who have had an allergic reaction to a previous flu vaccine.
The injectable flu shot (but not the nasal spray) has been shown to be safe for many people with egg allergies. Your doctor will need to assess whether you should have a flu shot if you are allergic to eggs. Be sure to tell your health care provider about this and any other allergies you may have before you are given your flu shot.
You can reduce your risk of getting the flu by washing your hands regularly using soap and warm water or an alcohol-based hand sanitizer. Also, cough or sneeze into a tissue or into your sleeve. Dispose of the tissue right away. If you have flu symptoms, stay home from work or school and avoid contact with people who are at a high risk of flu complications (e.g., seniors, nursing home residents).
For more information, please contact Lawrence Leung, Pharmacist/Owner of Forest Hill Pharmasave, 491 Eglinton Ave W, Toronto. Tel 416-619-7768 email: email@example.com