Health Tips

Seasonal influenza, or commonly known as flu, is an acute respiratory infection caused by influenza viruses. Water droplets from coughs and sneezes help spread the virus. It has similar symptoms to the common cold, but they are not the same thing. Influenza infection can become more severe than the cold and can result in death.

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Differences between influenza and the common cold

Source: Immunise4Life

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Key Statistics

The World Health Organization (WHO) estimates that influenza causes up to 650,000 deaths worldwide every year. 

A systematic review and meta-analysis published in The Lancet estimated there were 28,000-111,500 deaths in children younger than 5 years attributable to influenza-associated ALRI in 2008. 99% of these deaths occurring in developing countries. 

Meanwhile in Malaysia, the study, Influenza Surveillance in Hospitalised Patients with Acute Respiratory Symptoms in 2 Klang Valley Hospitals, identified 14% of influenza cases among its 350 subjects enrolled. This incidence rate is higher than the originally estimated 10%.  Long story short, Malaysia saw an increase in influenza cases recently. 

In temperate climates, seasonal epidemics occur mainly during winter, while in tropical regions, influenza may occur throughout the year, causing outbreaks more irregularly.

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A closer look at the influenza viruses

There are 4 types of seasonal influenza viruses, types A, B, C and D. Influenza A and B viruses circulate and cause seasonal epidemics of disease.

• Influenza A viruses are further classified into subtypes according to the combinations of the hemagglutinin (HA) and the neuraminidase (NA), the proteins on the surface of the virus. Currently circulating in humans are subtype A(H1N1) and A(H3N2) influenza viruses. The A(H1N1) is also written as A(H1N1)pdm09 as it caused the pandemic in 2009 and subsequently replaced the seasonal influenza A(H1N1) virus which had circulated prior to 2009. Only influenza type A viruses are known to have caused pandemics.

• Influenza B viruses are not classified into subtypes but can be broken down into lineages. Currently circulating influenza type B viruses belong to either B/Yamagata or B/Victoria lineage.

• Influenza C virus is detected less frequently and usually causes mild infections, thus does not present public health importance.

• Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.

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The influenza viruses are cunning

Because influenza viruses, particularly Type A and B, mutate constantly to evade our immune system and wreak havoc on global health. Influenza viruses can mutate in two different ways:

• Antigenic drift

These are small mutations in the genes of influenza viruses that can lead to changes in the surface proteins of the virus: HA (hemagglutinin) and NA (neuraminidase). Our immune system recognises the influenza virus through these surface proteins. Once influenza viruses changed its surface proteins, our immune system can no longer recognise it and orchestrate necessary antibodies production to fight against them. 

The changes associated with antigenic drift happen continually over time as the virus replicates. This is the main reason why people can get the flu more than one time, and it’s also a primary reason why the flu vaccine composition must be reviewed and updated each year (as needed) to keep up with evolving influenza viruses.

• Antigenic shift

This is an abrupt, major change in an influenza A virus, resulting in new HA and/or new HA and NA surface proteins in influenza viruses that infect humans. One way shift can happen is when an influenza virus from an animal gains the ability to infect humans. Such a shift happened during the year 2009 H1N1 viruses pandemic. Nevertheless, the antigenic shift happened less frequently.

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Vaccination

The most effective way to prevent the flu is vaccination. WHO has different recommendations on the composition of vaccination to be given based on geographical locations. However, for an equator country like Malaysia, the influenza season is rather unpredictable, and hence no specific recommendations are given.

Flu vaccines consist of the inactivated parts of influenza virus strains or weakened influenza virus. They can be given via injections (flu shot) or intranasal route (nose spray). Most of the influenza vaccines in the market contain eggshells components, thus people with egg allergies should not take them.

Nonetheless, there is a recently approved influenza vaccine that is neither inactivated or weakened and does not contain any egg protein. They are recommended for patients aged 18 years old who are allergic to egg proteins. 

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How successful the influenza vaccine is?

• Recent studies show that flu vaccination reduces the risk of flu illness by between 40% and 60% among the overall population during seasons when most circulating flu viruses are well-matched to the flu vaccine. 

• Not only that, but the vaccine also reduced both children’s and elderly’s risk of flu-related hospital admission by 74% and 40% respectively. 

• Pregnant women are also protected during and after pregnancy if they take the flu shot.

• In cases which people still get influenza after vaccination, the vaccines reduce the severity of the illness. 

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Who should take the flu shot?

The following groups are high-risk groups for influenza. They are recommended to take influenza vaccinations annually:

• All persons aged ≥6 months without contraindications 

• Children aged 6-59 months

• Adults aged ≥50 years

• Those who are immunocompromised, including that, is caused by human immunodeficiency virus (HIV) and medications

• Individuals with chronic lung (including asthma, a chronic obstructive pulmonary disorder, cystic fibrosis), cardiovascular (congenital heart disease, congestive heart failure, coronary artery disease except for isolated hypertension), kidney, liver, hematologic (including sickle cell anaemia) metabolic disorders (including diabetes mellitus)

• Individuals who are morbidly obese [i.e body mass index (BMI) ≥40]

• Children and adolescents 6 months to 18 years of age currently receiving Aspirin- or salicylate-containing medications who will be at increased risk for Reye syndrome after a bout of flu

• Women anticipating pregnancy and pregnant women during the flu season. The World Health Organization (WHO) considers the vaccine safe at any gestational age of pregnancy

• Poultry workers, pig farmers and those in pig-slaughtering industry

• Caregivers or other individuals who live with high-risk individuals

• Healthy household members and caregivers of high-risk individuals

• Healthcare workers

• Residents of institutions for the physically and mentally disabled 

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Get your flu shot today with Doc2Us® partner, AMC Medical Clinic, Seremban via drive-thru! You may make your appointment at https://qmed.asia/AMCor call AMC Medical Clinic at 06-601 2828.

Chat with Doc2Us® doctors and healthcare professionals today! Download the Doc2Us® app on http://onelink.to/doc2us or use our webchat https://web.doc2us.com/

World Immunization Week 2020 is an initiative by the World Health Organization (WHO) to promote the use of vaccines to protect people of all ages against disease. Read more about the campaign at https://www.who.int/news-room/campaigns/world-immunization-week/world-immunization-week-2020

Doc2Us® would like to encourage everyone to take necessary immunizations and to prevent the preventable. #VaccineWorks

References:

1. https://www.who.int/en/news-room/fact-sheets/detail/influenza-(seasonal)

2. https://specialty.mims.com/influenza/management

3. https://www.cdc.gov/flu/highrisk/index.htm

Written by

Ms.Toh Ker Ro