Dear readers,
This document is provided in order to clarify the recent questions in my twitter account and to also explain the differences between seasonal influenza & pandemic influenza. I have adopted concrete WHO guidelines in this write up, simplified for the community.
Before I start let me explain:
- Pandemic; A pandemic is a global disease outbreak. It is determined by how the disease spreads, not how many deaths it causes.
- Seasonal Flu; Seasonal flu is a contagious respiratory illness caused by flu viruses. It spreads between people and can cause mild to severe illness.
Source: blogs.sacbee.com
Seasonal influenza;
Seasonal influenza viruses circulate and cause disease in humans every year. In temperate climates, disease tends to occur seasonally, spreading from person-to-person through sneezing, coughing, or touching contaminated surfaces. Seasonal influenza viruses can cause mild to severe illness and even death, particularly in some high-risk individuals. Persons at increased risk for severe disease include pregnant women, the very young and very old, immune-compromised people, and people with chronic underlying medical conditions. Seasonal influenza viruses evolve continuously, which means that people can get infected multiple times throughout their lives. In other words, you can get H1N1 multiple times.
What is Influenza A, B ,C?
There are 3 large groupings or types of seasonal influenza viruses, A, B, and C.
Type A influenza viruses are further divided into subtypes according to the specific variety and combinations of two proteins that occur on the surface of the virus, the hemagglutinin or “H” protein and the neuraminidase or “N” protein.
Currently, influenza A (H1N1) in Sabah are the circulating seasonal influenza A virus subtypes. This seasonal A (H1N1) virus is the same virus that caused the 2009 influenza pandemic, as it is now circulating seasonally.
In addition, there are two type B viruses that are also circulating as seasonal influenza viruses, which are named after the areas where they were first identified, Victoria lineage and Yamagata lineage.
Type C influenza causes milder infections and is associated with sporadic cases and minor localized outbreaks. As influenza C poses much less of a disease burden than influenza A and B, only the latter two are included in seasonal influenza vaccines.
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Pandemic influenza;
A pandemic occurs when an influenza virus which was not previously circulating among humans and to which most people don’t have immunity emerges and transmits among humans. These viruses may emerge, circulate and cause large outbreaks outside of the normal influenza season. As the majority of the population has no immunity to these viruses, the proportion of persons in a population getting infected may be quite large. Some pandemics may result in large numbers of severe infections while others will result in large numbers of milder infections, but the reasons behind these differences are not completely understood. The most notorious pandemic for which data are available was the “Spanish Flu” in 1918-1919 which caused an estimated 20-40 million or more deathsworldwide. Subsequent pandemics in 1957 and 1968 resulted in many fewer deaths in spite of large portions of the world’s population being susceptible to infection. In 2009, a strain of influenza A (H1N1) virus which had not ever been seen before, emerged, spread across the world and caused the 2009 H1N1 pandemic. This pandemic A (H1N1)2009 virus has been widely circulating across the globe since 2009, and is now established in human populations as a seasonal influenza virus, as described above. Currently there is no longer a pandemic virus circulating in the world.
Conclusion H1N1 in Sabah;
Sabah health officials detected H1N1 flu virus at the Likas Women’s and Children’s hospital. Hospital director Dr Tan Bee Hwai via StarOnline said five children and two adult caregivers had been tested positive for the flu virus.
Influenza A (H1N1) 2009 virus that has been widely circulating across the globe since 2009, is now a seasonal influenza virus. A pandemic only occurs when an influenza virus has not previously been circulating among humans. For instant Egypt, 85 % of flu cases reported recently in Egypt are due to H1N1, this is not unusual as H1N1 has become seasonal flu.
In view of that, there is NO NEED to panic, the priority for now is to stop the transmission which includes quarantine protocols and getting everyone to practice personal hygiene, for example washing hands and the use of proper face masks. So remember, seasonal influenza viruses can only cause mild to severe illness, particularly in some high-risk individuals; pregnant women, the very young and very old, immune-compromised people, and people with chronic underlying medical conditions.
Lastly, do remember to keep yourself updated with Malaysian Medical Gazette for latest updates on current health issues.
Dr. Dhesi BR is the founder of Malaysian Medical Gazette pursuing his PhD in public heath at UniMas, Sarawak. Learn more about him at the Team Page.
This is the personal opinion of the writer and does not necessarily represent the views of The Malaysian Medical Gazette.
[This article belongs to The Malaysian Medical Gazette. Any republication (online or offline) without written permission from The Malaysian Medical Gazette is prohibited.]
Reference:
- 1. CDC FLU : http://www.cdc.gov/flu/
- 2. WHO; Flu Pandemic : http://www.who.int/influenza/en/