Home > Influenza(H1N1), Influenza(H1N1) > Everything you ought to know about the flu

Everything you ought to know about the flu


Well, not exactly everything, but a lot.

What is “the flu”?

Influenza, or “the flu” is an extremely contagious respiratory illness caused by influenza A or B viruses. Flu appears most frequently in winter and early spring. The flu virus attacks the body by spreading through the upper and/or lower respiratory tract. There are 3 types of flu viruses, A, B and C which can cause the flu, and new strains (especially the A type) evolve every few years.

Type A viruses are responsible for major flu epidemics every few years. Type B is less common and generally results in milder cases of flu. However, major flu epidemics can occur with type B every three to five years. There is a third type of virus, C, which also can infect but does not produce flu symptoms.

What are the symptoms/effects of the flu?

Besides generally making one feel miserable, here is a list of some of the most typical flu symptoms/effects.

  • Headaches
  • Severe aches and pains in the joints and muscles and around the eyes
  • Cough
  • Respiratory congestion
  • Fever
  • Chills
  • Fatigue & exhaustion
  • Severe flu can lead to pneumonia
  • Sore throat and watery discharge from your nose

Are there any complications that can arise from the flu?

The most common flu complications include viral or bacterial pneumonia, muscle inflammation, and infections of the central nervous system or the sac around the heart. Other flu complications may include ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.

Those at highest risk for flu complications include adults over 50, children ages 6 months to 4 years, nursing home residents, adults and children with heart or lung disease, people with compromised immune systems (including people with HIV/AIDS), and pregnant women.

How does flu spread?

The flu is spread from person to person through respiratory secretions and typically sweeps through large groups of people who spend time in close contact, such as in daycare facilities, school classrooms, college dormitories, military barracks, offices, and nursing homes.

Flu is spread when a person inhales droplets in the air that contain the flu virus, make direct contact with respiratory secretions through sharing drinks or utensils, or handle items contaminated by an infected person. In the latter case, the flu virus on your skin infects you when you touch or rub your eyes, nose, or mouth. That’s why frequent and thorough hand washing is a key way to limit the spread of influenza. Flu symptoms start to develop from one to four days after infection with the virus.

Will one catch the flu if one goes out in the cold or gets wet by cold rain?

No. The flu is a viral infection; you need to come in contact with the flu virus to get infected. Feeling cold or being wet does not give you the flu. It might give you a runny nose though and other symptoms that may be reminiscent of the flu, but it does not cause a flu infection.

What are the symptoms/effects of the flu vaccine?

The most common side effects of the flu vaccine (both inactivated and LAIV) include mild:

  • Swelling at the site of the injection (inactivated only)
  • Headache
  • Cough
  • Body ache
  • Fever

When should one get the flu vaccine?

As soon as it is available.

How many types of flu vaccines are there?

There are two types of flu vaccine. Inactivated and LAIV. The inactivated vaccine is given as a shot, generally in the arm, while the LAIV version is a nasal spray. The main difference between the two is that the inactivated, or the shot, contains dead viruses, whereas the LAIV version contains alive, but extremely weakened, viruses. Because of that, the spray is expected to be more effective in inducing an immune reaction than the shot.

Why is the flu vaccine different every year?

Two of the three flu viruses are responsible for causing flu, type A and type B. Type A has 16 subtypes, while Type B is not categorized by subtypes.  They both can mutate, especially type A which results in new strains every few years. Every given year, any combination of various strains of the various subtypes of A and of Type B can be in circulation and causing flu.

Every given year, both the LAIV and Inactivated vaccine contain three strains of influenza virus that are chosen each year based on what scientists predict will be the circulating viruses for the flu season. Given the long production times, it is impossible to know for sure which strains will be prevalent in the upcoming season, so every year scientists have to do their best to predict what they think will be the prevalent strains. Usually this process is done months ahead of the actual flu season. This is why the flu vaccine is different each year, and why we have to get re-vaccinated each year.

Which strains does the 2010 vaccine protect against?

Every year, the flu vaccine, protects against 3 specific strains of viruses that cause flu. The 2010 vaccine protects against two A viruses and one B virus. This year the vaccine protects against these 3 strains:

  • an A/California/7/2009 (H1N1)–like virus (Swine Flu)
  • an A/Perth/16/2009 (H3N2)–like virus
  • and a B/Brisbane/60/2008–like virus

Can you get the flu from the flu vaccine?

No! You cannot get the flu from the flu vaccine. You may, however, experience some flu-like symptoms, which can be experienced from any vaccine in some cases and doesn’t have anything to do with the actual disease you’re being inoculated against.

How effective is the flu vaccine?

The effectiveness of the flu vaccine depends on the strains in circulation and the strains the vaccine prevents from. When the vaccine viruses and circulating viruses are well-matched, the vaccine can reduce the chances of getting the flu by 70% to 90% in healthy adults.

Can you get the flu, even if you get vaccinated?

Yes. Firstly, as we already saw, the 3 strains in the flu vaccine have to be guessed in advance of the flu season. If there is a good match between the predicted strains and the actual strains in circulation, the vaccine will provide good protection. On the other hand, even if there is a perfect match, no vaccine is 100% effective, so even then a person who got vaccinated may still develop the flu. However, in general, people who are vaccinated experience milder symptoms than the non-vaccinated ones.

Who should get the flu vaccine?

Except for high risk groups that are advised to skip the vaccine, it is recommended that everyone over 6 months of age should get the flu vaccine.

Who should not get the flu vaccine?

Anyone with a severe allergy to eggs or egg products should not get a flu shot. Other people who should not get a flu shot include:

  • Infants under 6 months old.
  • Anyone who has had a severe reaction to a past flu shot or nasal spray.
  • Someone with Guillain-Barre syndrome.
  • People with moderate to severe illness with a fever; they should be vaccinated after they have recovered.

How Long Am I Contagious After I Get the Flu?

You are contagious for up to seven days after the onset of the flu, although the flu virus can be detected in secretions up to 24 hours before the onset of symptoms. This means you might transmit the flu virus a full day before your flu symptoms begin.

In young children, the flu virus can still be spread in the secretions even into the second week of illness.

How Can I Prevent the Flu?

To prevent the flu, be sure to keep your hands clean — making sure to wash them frequently to remove germs — and get a flu shot. The CDC develops a flu vaccine based on the type A strain that they believe will be most prevalent in the coming flu season. This is the vaccine you get with the annual flu shot or FluMist nasal spray.

Give me some statistics please?

-Every year during flu season, 1 in 20 Americans will contract the disease. Some years incidence can be as high as 1/5.

-Annually there are about 200,000 hospitalizations and an average of 23,600 annual deaths from the flu  in the US alone.


Sources

WebMD

Flu.gov

CDC Flu Website

World Health Organization Influenza Page

Advertisements
  1. October 20, 2010 at 5:40 PM

    I did a little explanation on genetic drift and shift last year, as well, which if you’re interested you could see here: http://redrabbitslife.wordpress.com/2009/04/26/influenza-virology-for-fun-and-profit/

  1. October 20, 2010 at 12:21 PM

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: