With about nine flu pandemics annually during the past 300 years - the most recent being the 2009 Swine flu or H1N1 - flu epidemics are estimated to cause from 3 million to 5 million cases of severe illness and between 250000 and 500000 deaths worldwide.
And while the signs and symptoms of flu are well documented - such as having a sore throat, fever, headache, muscle aches and soreness, congestion, severe tiredness or in rare cases vomiting and diarrhoea - how much do we know about flu?
The influenza virus was first identified in 1933, says Professor Cheryl Cohen, co-head of the Centre for Respiratory Disease and Meningitis at the National Institute for Communicable Diseases.
“There are two types of seasonal influenza viruses affecting humans; influenza A and B. Seasonal influenza viruses experience regular progressive change in their surface structures (‘antigenic drift’).
“The antigenic drift of influenza virus necessitates annual updates of the vaccine composition to optimise the match with circulating strains,” Cohen says.
“In contrast, antigenic shift occurs when a completely new subtype of influenza virus appears and can result in the emergence of a new virus with the potential to cause a pandemic. These pandemic strains eventually become seasonal strains.”
According to Cohen, anti-viral medications that may decrease the severity of the illness and prevent complications first became available in 1999.
And since then, more effective vaccines with a higher dose or more substances included (that improved the effectiveness of the vaccine) have been developed in recent years.
Waheed Abdurahman, a Clicks pharmacist, says that over the past decade, the flu vaccine has improved in terms of having fewer toxic preservatives to avoid allergic reactions and generally, there has been been an improved availability through distribution, as well as consumer-friendly pricing.
Cohen emphasises that the flu vaccine is the primary means for preventing seasonal flu infection with vaccines updated each year on the basis of global influenza surveillance data.
The annual vaccine contains strains corresponding antigenically as closely as possible to the three seasonal influenza strains prevalent in human populations: influenza A H1N1, influenza A H3N2 and influenza B.
“Vaccines should be given sufficiently early to provide protection for the winter, as soon as the vaccine becomes available, though it is never too late to vaccinate. A protective antibody response takes about two weeks to develop,” Cohen says.
“Vaccine effectiveness varies from year to year and differs amongst age groups, and is dependent on the age and health of the person being vaccinated and the match between the virus strains in the vaccine and those circulating in the community.”
While the timing of the flu season varies from year to year, influenza virus circulation occurs mainly during the winter months of May to August, but may start as early as April, and as late as July.
“We cannot predict which strain will be the dominant strain. During the 2016/17 season influenza A (H3N2) predominated in both Europe and North America, as well as in northern Africa, east, south-east, and south Asia, with 98.7% of influenza A detections subtyped as A(H3N2) by national influenza laboratories from 74 countries,” Cohen says.
The most common side-effects of the vaccine are local swelling, redness or tenderness at the site of the injection, and more rarely low-grade fever or myalgia (muscle pain).
However, if these reactions occur, they begin soon after vaccination and last no more than one or two days.
“As the vaccine virus is an inactivated virus, it cannot cause influenza,” Cohen says.
“A common myth is that the flu vaccine can cause a cold or flu. This is not possible because the vaccine does not contain live virus.
“The time when we regularly give the vaccine coincides with the period when respiratory viruses circulate. Therefore it can occur that a person coincidentally gets a viral infection around the time of getting the vaccine.”
Mogologolo Phasha, chairman of the Independent Community Pharmacy Association, warns that many people die every year as a result of complications from flu, with most deaths occurring in people considered to be “high risk”.
Those considered high risk are "pregnant women, children between the ages of six months and 5 years, people older than 65, those with HIV/AIDS, chronic disease sufferers and those who work and live in densely populated areas and high traffic sites - teachers, students and cashiers in busy retail outlets are examples”.
Cohen says that while influenza does not cause specific birth defects, vaccinating pregnant women could prevent flu in pregnancy or in the newborn baby and this could reduce the chances of severe influenza complications in the baby.
And if you do contract the virus, Cohen says, “stay in bed, drink plenty fluids, treat the symptoms, eg Panado for pain, and do not exercise for several weeks after recovery”.
“There are antiviral medications that may decrease the severity of the illness and prevent complications but these must be prescribed by a doctor. Antiviral treatment is most effective when initiated within 48 hours of the onset of illness.”