Dr Zafar Nowshad Wani

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 common cold is also caused by viruses, flu and common cold differ in several ways .In  India, including J&K, flu almost always strikes between November and April, but this year amid COVID-19 pandemic it seems people have already taken flu shots as it may infect more and more people in coming winters. 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 “off” year.

Most people who get flu will recover within 1 to 2 weeks, but some people are at risk of developing complications such as pneumonia.

Causes

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. Flu is most easily spread in crowded places such as schools and offices

There are three families of influenza virus: A, B, and C. Type C more commonly affects ducks, geese, turkeys, and chicken, but it has also been involved in a small percentage of human cases. Type B mainly affects humans and causes a milder disease, and it changes very little from year to year.

Type A influenza poses the most serious threat to humans. Strains of this type have also been found in birds, humans, horses, pigs, seals, whales, and ferrets. Viruses that affect two different species sometimes combine and mix-and-match genetic information to create a new strain that nobody is immune to and for which no vaccine has been prepared.

There are potentially infinite new varieties of type A influenza. Avian flu is a type of influenza A that had been seen only in birds, including chicken and ducks, until 1997 when the first human case was reported in Hong Kong . Swine flu is another type of influenza A that is normally found in pigs. Swine flu is passed from pig to pig, and although it usually only infects pigs, there have been periodic infections in humans, resulting in H1N1 flu virus (human swine flu). Most of these cases occur in people with direct exposure to pigs (e.g., people working on pig farms). Person-to-person transmission of the H1N1 flu virus (human swine flu) does occur, but it is not clear how easily the virus is spread among people.

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.

Symptoms and Complications

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 diarrhoea are rare in adults but more common in children.

Since many people think they have flu when it’s actually a bad cold, here’s a quick guide to help you tell the difference:

For most people, 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.

Diagnosis

Since the symptoms of an influenza infection are very differentfrom the common cold, the diagnosis can bemade 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 flu by taking a throat swab and testing it for the virus. This is rarely needed.

Treatment and Prevention

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.

Zanamivir and oseltamivir are antiviral medications that can be used to treat Influenza A.

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.

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)
  • diabetes
  • 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

  • cancer
    • 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 neurodevelopment 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).

(Author is a Microbiologist at STDC Srinagar. Feedback at [email protected])

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