Assoc Prof Dr Tan Toh Leong is an emergency medicine physician and medical lecturer with the Department of Emergency Medicine , Faculty of Medicine , Universiti Kebangsaan Malaysia ( UKM ) and President & Founder of Malaysian Sepsis Alliance ( MySepsis )

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ASSOC PROF DR DING CHUAN HUN

Assoc Prof Dr Ding Chuan Hun is a clinical microbiologist and medical lecturer with the Department of Medical Microbiology & Immunology , Faculty of Medicine , UKM and a member of MySepsis .

To add to the confusion , there is a virus named parainfluenza and even a bacterium named Haemophilus influenzae . In stark contrast to their names , these pathogens do not cause influenza .

Thus , while many people claim to have “ flu ” when they experience fever , cough , rhinitis ( stuffy or runny nose ) and pharyngitis ( sore throat ), this may not necessarily be spot-on as common cold viruses can also bring about identical symptoms . Nonetheless , distinguishing influenza from the common cold is not merely an academic exercise , as flu symptoms are generally more intense , with high-grade fevers , body aches and headaches being more common occurrences . Additionally , although rare , complications such as pneumonia ( infection of the lungs ), myocarditis ( inflammation of the heart muscle ) and encephalitis ( inflammation of the brain ) are more likely to be associated with influenza .

There are four types of influenza viruses ( A , B , C and D ), and humans are not the sole

natural hosts of the viruses . Influenza A and B viruses are responsible for seasonal disease epidemics . Influenza A viruses have even unleashed global pandemics . Fortunately , influenza C viruses cause mild human infections that do not result in human epidemics or pandemics . In contrast , influenza D viruses principally infect cattle ( with possible spillover to other ruminants ) but do not cause clinical disease in humans .

TYPES OF INFLUENZA

Among the four influenza virus types , influenza A has the widest host range , and distinct influenza A viruses that infect the same cell can exchange genetic material with each other ( a phenomenon known as reassortment ). The reassortment of avian with human influenza A viruses is particularly worrying , as this has the propensity to trigger pandemics .

The most recent influenza pandemic occurred in 2009 ( a decade before the Covid-19 pandemic ) following the detection of a novel influenza A ( H1N1 ) virus in North America – the culprit was a reassortant virus which possessed genetic material derived from humans , swine and birds . It , therefore , makes perfect sense that influenza vaccines need to at least confer protection against influenza A and B viruses . However , as these viruses constantly evolve through genetic mutations ( known as antigenic drift ), it is customary to revise the influenza vaccine composition periodically .

Every year , the World Health Organisation releases two influenza vaccine composition recommendations , one intended for the northern hemisphere and another for the southern hemisphere . As Malaysia is situated along the equator , either the northern or southern hemisphere vaccine may be accepted .

The intended hemisphere notwithstanding , each vaccine formulation grants

protection against two influenza A viruses and at least one influenza B virus . Trivalent vaccines protect against two influenza A viruses plus one influenza B virus , while quadrivalent vaccines provide defence against two influenza A viruses plus two influenza B viruses . The vaccine should be administered annually , typically as a jab into the muscle or fat tissue of the arm .

PREGNANCY IS NOT AN EXCLUSION CRITERION

In support of the United Nations ’ Sustainable Development Goal 3 which promotes good health and well-being for all at all ages , any individual above the age of six months may be vaccinated against influenza . Specific target groups have also been identified , including healthcare workers , persons aged 50 years and above , those performing religious pilgrimages , institutionalised persons as well as obese individuals .

Pregnancy is not an exclusion criterion for influenza vaccination because the vaccines ( with the notable exception of the nasal spray influenza vaccine which is not widely obtainable yet in Malaysia at the time of writing ) are not live vaccines . However , it is important to note that the manufacturing process of many influenza vaccines currently available in Malaysia entails culturing viruses in embryonated chicken eggs .

Consequently , such vaccines should not be administered to individuals who are allergic to egg-based products . Lastly , it should be emphasised that no influenza vaccine can guarantee 100 per cent protection , so other preventive measures need to be adopted too .

Like SARS-CoV-2 , which is transmitted through the respiratory route , measures that reduce the risk of Covid-19 such as social distancing and donning face masks in crowded settings , can similarly help to prevent influenza . – The HEALTH