Blog, Immunization, Influenza

The ABC of influenza and “the flu” for 2016–2017 season

Influenza remains a common infection in the United States and the main reason is because it is a contagious viral illness, is spread by contact and droplet. There are two species of influenza, Influenza A and Influenza B however for our purposes and for the most part bot are often managed the same way.

Every year scientists type the strains of influenza circulating and you will hear strains described as A/H1N1, A/H3N2, B. These are the main ones that cause most epidemics however with antigenic drift, humans are rarely able to build enough immunity before the strain changes slightly and once again infects us.

Children are most affected because of their immunological immaturity. Their immune system is relatively inexperienced with influenza viruses thus they are unable to neutralize the virus in time.

How does flu spread?

It infects the the entire airway from nose through the throat all the way down to the lungs. These are “ high traffic wind tunnels” and as such the infected person is able to shoot virus carrying droplets far away from them, infecting others that inhale the droplets.

There could also be spread when these droplets get into our mouth, when we touch a surface that have the infection and then touch our mouth, eyes or nose.

What are the usual symptoms and signs of influenza

In the older children and adults, onset is rather sudden. Aches and pains in the muscles and bones is an early herald of infection. This is usually accompanied by severe headaches, fever and chills. Affected persons often feel very tired.

There are the other symptoms which we may see in other viral respiratory illness such as cough, sore throat and runny nose, but the more intense symptoms usually overshadow and keep the patient very sick.

I have seen a small number of children develop vomiting, tummy pain and watery stools but this is not seen in adults.

In the very young, under 2 years old, they may get very sick very fast and may look like they have life-threatening bacterial infection called sepsis.

3 Dimensional model of influenza virus 3d graphical representatiWhat are the unusual symptoms and signs of influenza

These clinical signs and symptoms may be seen sometimes in influenza.

  1. Croup: a condition where the patient has swelling of the inner lining/surface of the throat, causing a certain hoarseness of the voice quality. This will often lead to a barking like sound if the individual coughs. It is more common in Influenza A.
  2. Asthma exacerbation (increased symptoms): In known asthmatics, they may develop an increased need for use of their inhaler or other asthma medications beyond what would normally work for them.
  3. Myositis: Muscle aches especially with the calf muscles.
  4. Myocarditis: Inflammation of the heart muscles. Doctors suspect this if the person has unusual physical examination findings in the cardiovascular system. It is not common but can happen.
  5. Parotitis: Inflammation and pain of the parotid gland. The parotid gland lies on both sides of the face, kind of over the muscle area that we see moving when we chew. It may swell and be warm and the doctors can usually tell that something is amiss.
  6. Encephalopathy: a somewhat abnormal functioning of the brain due to metabolic factors which may have been triggered by an infectious agent within or outside the brain.
  7. Transient skin rash: these are flat with a few raised areas (maculopapular rash). May be missed in dark skinned individuals but looks more red in lighter persons.

When do the symptoms of influenza start?

The symptoms can start between one and 4 days after the person has come in contact with the viral agent. The average is two days.

How long do the symptoms of influenza last?

The acute symptoms last 2 to 5 days, but the cough and tiredness (fatigue) can last several weeks.

When is the person infected with influenza contagious?

This is really bizzare and I want you parents to pay attention here. A healthy person may start spreading influenza up to 1 day before they themselves develop symptoms.

Yes, you can not give what you do not have, but you can give what you do not know that you have!

People tend to spread the virus up to 5 to 7 days after onset of symptoms.

What are the complications of influenza?

According to the CDC “ Young children, adults aged 65 years and older, pregnant women, and people with certain chronic medical conditions are among those groups of people who are at high risk of serious flu complications, possibly requiring hospitalization and sometimes resulting in death. For example, people with chronic lung disease are at higher risk of developing severe pneumonia.

Other complications that are more common include ear infections and sinus infections.

How do the doctors diagnose flu?

Influenza is challenging to diagnose without laboratory testing because there are many other illnesses that have similar symptoms. This is more so in children.

As I have outlined above, there are so many symptoms so the doctors carry out laboratory tests to diagnose flu. These tests vary in their nature as well as their accuracy. Thus a person may have the flu but the tests will come back negative.

The rapid influenza detection tests RIDTs sometimes have false negative, so a negative test is not sine-qua-none fact that there is no influenza infection present. Many doctors use a combination of clinical judgement based on the symptoms and signs elicited, the history (surrounding story) and the test results to make a decision on diagnosis.

We do not have this challenge if the test comes back positive.

In the testing, the nurse or doctor would stick a swab into the throat or deep in the nasopharynx. It is very very uncomfortable. No not painful, just plain “icky”.

The rapid test takes about 30 minutes while the specimen may also be sent off to the laboratory and comes back after about 2 days a PCR is done. In some centers they would do the culture which is growing the organism in the lab. In such cases it may take anywhere from 3 to 7 days before you get a result.

How is influenza treated?

Okay, you have been diagnosed with influenza and you are happy. Time for treatment?

Erhm…. It is still complicated (no you do not have a complication, it is just complicated).

There are two groups: as the CDC says here,

  • Antiviral treatment is recommended as soon as possible for patients with confirmed or suspected influenza who have severe, complicated, or progressive illness or who require hospitalization.
  • Antiviral treatment is recommended as soon as possible for outpatients with confirmed or suspected influenza who are at higher risk for influenza complications on the basis of their age or underlying medical conditions; clinical judgment should be an important component of outpatient treatment decisions.

The medications known to be effective in more than 99% of cases according to the CDC are oseltamivir (Tamiflu)and zanamivir (Relenza). Amantadine and Rimantadine are no longer recommended because of resistance and also because the first two medications above are effective up to 99% of the time.

How do we prevent influenza infection?

Wow. I am glad you asked. I will tell you.It is very easy.

Go and get the flu shot.

First off, everybody gets a shot. The reason is that the nasal spray which some people like has been found not to be effective enough recently to keep on giving it. The CDC Advisory Committee on Immunization Practices made that determination and published the guidance this past June, 2016.

They found that the nasal spray Live attenuated influenza vaccine LAIV was 3% effective compared to the shot inactivated influenza vaccine IIV which was up to 63% effective.

You may be wondering why I said everybody gets a shot. Well, if you do not get a shot this season, you are a potential risk to your community. You could get the influenza virus, spread it to a child who is under 6 months thereby putting the child in mortal danger.

What we expect based on CDC plans for the influenza shots this year can be seen here.

What is the appropriate dosing age for young children? (copied from www.cdc.gov)

[I expect this to be the same for 2016–2017]

I: The following children will require 2 doses of influenza vaccine, administered at least 4 weeks apart, for 2015–16:

1. Children aged 6 months to 8 years who have never been vaccinated against influenza or for whom vaccination history is unknown;

2. Children who have not received at least two doses of seasonal influenza vaccine (trivalent or quadrivalent) before July 1, 2015.

II: The following children will require only one dose of influenza vaccine for 2015–16:

1. Children 6 months through 8 years who have received at least two doses of seasonal influenza vaccine (trivalent or quadrivalent) before July 1, 2015.

2. Children 9 years of age and older.

For inactivated (injectable) vaccine (IIV), the dose for children aged 6–35 months is 0.25 mL and the dose for children aged 36 months-9 years is 0.5 mL.

How is influenza researched by the CDC?

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