The winter months are synonymous with the flu in South Africa. Similar to other countries in the southern hemisphere, South Africa has an annual influenza season stretching from April to August.

Influenza (flu) is an acute respiratory illness caused by an infection of the respiratory tract with the influenza virus. Influenza is spread through respiratory droplets which you breathe in or can pick up from contaminated surfaces. People infected with the influenza virus how a wide range of symptoms such as sudden onset of fever, muscle pains and body aches, cough, sore throat, blocked or runny nose and headache. For most people, recovering from flu involves a few days of mild symptoms which resolve with symptomatic treatment. But for some, the flu can be deadly.

The World Health Organization (WHO) estimates that there are over 1 billion flu cases occur each year. These include between three and five million cases of severe flu illness with people requiring hospitalisation and between 290,000 and 650,000 deaths each year. In severe cases influenza can spread to the lungs or weaken your lungs so that you get a bacterial infection. An infection of the the lower respiratory tract including the lungs is called pneumonia. In people with underlying heart or lung disease influenza infection can also cause worsening of these conditions.

Treatment for flu is mainly symptomatic. This includes bed rest and over the counter medicines to reduce fever like paracetemol. The best way to avoid getting ill is to get vaccinated. South Africa is currently seeing a spike in flu cases. As epidemiologists who research respiratory diseases, we urge those who haven't had a flu vaccine yet to do so. This will help protect the individual and those around them from severe illness.

Getting vaccinated

The first reason you should strongly consider getting vaccinated against the flu if you haven't done so yet is to protect yourself. Results from a modelling study we conducted using 2013-2015 data estimated an average of 10,737,847 influenza-associated illnesses and 11,536 deaths every year in South Africa.

Flu vaccines remain the most effective method available to prevent flu illness, especially severe illness. The main reason to get the flu vaccine is to lower your risk of being sick with flu.

Most individuals infected with the flu virus will have mild illness. But certain groups of people are at risk of having severe flu illness or having flu complications or death. The flu vaccine has been shown to lower the risk of severe illness or complications.

The groups who have a high risk of severe illness or complications include:

• pregnant women at any stage of pregnancy, including postpartum

• individuals with chronic medical conditions (such as cardiac diseases, chronic renal diseases, diabetes mellitus)

• immunocompromised people (such as people living with HIV, cancer patients)

• elderly individuals (over 65 years).

Individuals who fall in the groups above are strongly encouraged to get vaccinated for influenza each year.

Flu vaccination also prevents chronic health conditions from getting worse. For example, flu vaccination has been associated with lower rates of some cardiac events among people with heart disease.

If many people are vaccinated, it will also decrease the spread of influenza in communities. Specifically, health workers are encouraged to vaccinate as they are at risk of getting infected with influenza from their patients. They are also more likely to transmit the virus to their patients, who may be at risk of severe flu illness if not vaccinated.

Not too late

Ideally, flu vaccines should be administered ahead of the flu season around March or April as it takes approximately 14 days for the body to build immune responses to protect against infection.

However, it is never too late to get the flu vaccine as long as the influenza virus is circulating. It is recommended that people get vaccinated every year (season) because circulating vaccine strains differ each year. The previous vaccination may not protect against the new strain circulating. And the individual immunity wanes over time.

Namhla Bhenxa, an epidemiologist at the National Institute for Communicable Diseases, is the main contributor on this article.

Authors: Jocelyn Moyes - Medical Epidemiologist, National Institute for Communicable Diseases | Cheryl Cohen - Co-head of the Centre for Respiratory Disease and Meningitis, National Institute for Communicable Diseases | Sibongile Walaza - Medical Epidemiologist at the National Institute of Communicable Diseases and Lecturer at the School of Public Health, University of the Witwatersrand