Understanding RSV and Influenza: What You Need to Know

Dr. Shukri Raban, Paediatrician at Melomed Gatesville
DipHivMan (SA), MPhil (UCT)

Respiratory Syncytial Virus (RSV) and Influenza are two common respiratory illnesses that can be particularly serious for young children, older adults, and those with weakened immune systems. Although they can cause similar symptoms like coughing, fever, and congestion, RSV and Influenza are caused by different viruses and have distinct characteristics. This article will help you understand the differences between RSV and Influenza, so you can better protect yourself and your loved ones.

Respiratory Syncytial Virus (RSV)
RSV is a common virus that affects the respiratory tract. It is highly contagious and spreads through respiratory droplets when an infected person coughs or sneezes. RSV can cause a range of symptoms, from mild cold-like symptoms to more severe respiratory illness such as bronchiolitis and pneumonia. RSV is a significant cause of respiratory illness globally, particularly in young children and older adults. Young children are more likely to introduce RSV into the home, and to be infected. In South Africa, RSV poses a substantial burden on public health, contributing to hospitalisations and mortality, especially among infants and young children.

Universally, the majority of severe RSV disease occurs in younger children, under the age of one. In fact, RSV is the most common cause of bronchiolitis (inflammation of the small airways in the lungs) and pneumonia in this age group. Symptoms of RSV infection in infants may include coughing, wheezing, difficulty breathing, and a bluish colour of the skin due to a lack of oxygen.

In 2019, Respiratory Syncytial Virus (RSV) caused around 33 million cases of serious lung infections worldwide. Among children under 5 years old, there were about 3.6 million hospital admissions and over 100,000 deaths due to these infections. This means that RSV was responsible for about 2% of all deaths in children aged 0 to 5 years.

Most of these cases (over 97%) occurred in low- and middle-income countries, and about three-quarters of the affected children did not receive medical attention. RSV infections were most common in infants under 6 months old. However, about 80% of serious RSV cases in children under 5 years old happened in those aged 6 months to 4 years.RSV also poses a significant risk to older adults, causing severe illness in this age group as well.

RSV infections follow distinct seasonal patterns around the world. In South Africa, RSV is most common during the autumn and winter months. For 2024, the RSV season started in the first week of February. Apart from the disruption caused by the COVID-19 pandemic in 2020, the detection rate of RSV cases in 2024 has been similar to the average rates seen from 2016 to 2019 and from 2022 to 2023.

Each year in South Africa, it is estimated that between 178,000 and 443,000 children under the age of five will get infected with RSV. Before the COVID-19 pandemic, RSV was estimated to be responsible for about 44,615 hospitalizations and 490 deaths annually in children under five. Among children aged one to four years, there were 52 deaths each year due to RSV.

There is no specific treatment for RSV. Most cases can be managed at home with supportive care, such as rest, fluids, and medications to reduce fever. However, severe cases may require hospitalisation, especially for infants and young children who have difficulty breathing.

Prevention of RSV
Prevention measures include isolation of children with influenza-like symptoms (sick children should not go to crèches or schools for a few days), and teaching children (and adults looking after infants) to practice sneeze and cough hygiene. The use of prophylactic antibiotics for children with upper respiratory tract infections is not recommended.
The monoclonal antibody, palivizumab, administered monthly throughout the RSV season to preterm infants and children at high risk of severe RSV disease, has been shown to be effective for prevention. However, high costs and the need for monthly intramuscular injections throughout the RSV season limit its use. New maternal vaccines and long-acting monoclonal antibodies for RSV prevention in infants have been licensed in some areas such as the United States of America and Europe since 2023, but these products are not yet available in South Africa. Live-attenuated vaccines targeting children aged >6 months are also under development.

Influenza (Flu)
Influenza, commonly known as the flu, is also a viral infection that affects the respiratory system. It is caused by influenza viruses, primarily types A and B, which can change rapidly, leading to seasonal outbreaks of the flu. Like RSV, influenza is highly contagious and spreads through respiratory droplets.
The symptoms of influenza are similar to those of RSV and can include fever, cough, sore throat, runny or stuffy nose, muscle aches, fatigue, and headaches. Influenza can also cause serious complications, especially in young children, older adults, and people with certain underlying health conditions. These complications can include pneumonia, bronchitis, sinus infections, and ear infections. In South Africa, the flu season typically occurs during the winter months, from May to September. The influenza season started in week 17 (week starting 22 April 2024).

Unlike RSV, there are antiviral medications that can be used to treat influenza. These medications work best if started within the first 48 hours of illness and can help reduce the severity of symptoms and the duration of the illness.

To combat the flu, the South African government typically promotes vaccination campaigns. Ideally the influenza vaccine should be administered prior to the start of the influenza season because it takes about 2 weeks for antibodies to develop following vaccination. However, it is never too late to vaccinate. In South Africa, the flu vaccine is typically recommended for individuals who are at higher risk of complications from the flu, including:

• Adults aged 65 and older
• Children aged 6 months to 59 months
• Pregnant women (the vaccine protects the mother as well as their babies from flu illness and flu related hospitalizations for the first several months after their birth, when they are too young to get vaccinated)
• Individuals with certain chronic medical conditions (e.g. HIV/AIDS, diabetes, asthma and other lung diseases)

Conclusion
RSV and influenza are both respiratory viruses that can cause serious illness, particularly in vulnerable populations. While RSV primarily affects young children, influenza can affect individuals of all ages. RSV and influenza are a significant public health concern in South Africa, particularly among young children, and imposes a substantial burden on healthcare systems. Vaccination against influenza and practicing good hygiene, such as washing hands regularly and avoiding close contact with sick individuals, are important measures to reduce the spread of both RSV and influenza.