RSV is linked to childhood asthma – but we can’t yet say one causes the other

As winter approaches in Australia, respiratory viruses are everywhere. One of the main culprits is the RSV virus, which has caused over 145,000 infections across the country this year. Most of them are among children under five.

RSV is the leading cause of bronchiolitis and pneumonia (both chest infections) in newborn children. Every year at least one in 200 children children under five are hospitalized with RSV in Australia. Babies less than six monthsand especially children under three months of age, are most at risk.

The RSV virus infects respiratory tract and lungswhich causes the mucus in the respiratory tract to become very sticky. Juvenile children may experience coughing, wheezing, difficulty breathing and feeding problems.

Studies indicate that severe RSV infection in infancy may also increase the risk children with asthma. So what evidence is there linking RSV to asthma? And why might this link exist?

Relationship or cause-and-effect relationship?

Asthma is a chronic lung disease that affects: 11% of Australians. People with asthma often have difficulty breathing, coughing, and wheezing. This happens because their airways become temporarily narrower, usually due to triggers (for example, viral infections, dust, or pollen). Asthma often begins as wheezing in preschool. But for some people, it begins in adulthood.

When we talk about RSV and asthma, it is critical to consider the differences between association and causation. An association occurs when two events often occur together (for example, smoking and drinking coffee), while a causal relationship occurs when we know that one can cause the other (for example, smoking and lung cancer). While the association between RSV and asthma is well-established, a causal relationship it has not been proven yet.

To prove a causal relationship, certain criteria must be met. These include a temporal relationship (in this case, RSV infection must occur before asthma) and a plausible explanation (biological mechanism).

Some evidence suggests that RSV infections change the developing cells in the airways of infants and newborn children. This could mean that the protective or barrier function of the lining of the airways is altered, predisposing a child to become sensitized to allergens — when their immune system makes antibodies to something they encounter, such as grass or dust.

Allergen sensitization is a significant risk factor for asthma, so severe RSV infection may contribute to the development of asthma through sensitization to common environmental allergens. This is a possible biological mechanism, but we still need more research to confirm this.

Several studies show an association between severe RSV infection and recurrent wheezing and asthma in later childhood.

But what comes first? one studyChildren under 12 months of age who developed RSV bronchiolitis were followed for six years. Almost half (48%) were diagnosed with asthma before their seventh birthday.

Similarly in another testChildren hospitalized for RSV infection before the age of two were more likely to develop asthma by the age of 18 than those who were not hospitalized.

However, the researchers who conducted twin study concluded that the data were more likely to indicate reverse causation. That is, children with a predisposition to asthma were more likely to develop RSV requiring hospitalization.

We may be closer to the answer

The pendulum may be swinging towards causality. Recent findings from South Africa Birth Cohort Study showed that severe RSV infections were associated with both recurrent wheezing and subsequent impairment of lung function.

Some prior examination Studies conducted by this group showed that hospitalization for any respiratory infection, and particularly for RSV, was associated with recurrent respiratory infections and wheezing. Recurrent wheezing and decreased lung function are predictors of future asthma.

Other last examination Studies of more than 1,700 children in the United States have shown that avoiding RSV infection in infancy can prevent up to 15% of childhood asthma cases.

Recently, the possibility of vaccinating mothers and using monoclonal antibodies to prevent RSV infection has emerged, which will probably support answer this question once and for all.

Earlier this year, nirsewimab (a long-acting monoclonal antibody) became available for infants and newborn children through state programs in Western Australia, Queensland AND New South Wales. Nirsevimab works slightly differently than the vaccine, but is similarly administered as an injection.

In addition, the RSV vaccine Abrysvo was licensed in Australia this year for apply during pregnancy to protect the baby after birth. It is available to pregnant women to buy privately on prescription from a doctor, while South Australia recently announced it will provide Abrysvo free to pregnant women next year.

With these measures, hopefully we will see a reduction in RSV at a population level in the coming years. If we see a reduction in asthma at the same time, this may finally answer the question of causality.

Protecting children and communities

Although it is still not known whether RSV causes asthma, RSV and other viral infections can be especially problematic for people who already have asthma. In both cases adults in children with asthma, respiratory diseases of viral origin may have a more severe course and cause an exacerbation asthma symptoms.

RSV It is spread through coughing, sneezing, and close contact. There are many other viruses that spread in similar ways. Parents can support keep their children and others fit by encouraging children to cover their mouths and noses when coughing or sneezing and to wash their hands regularly.

Ensuring that children do not go to school, daycare, or other children when they are ill helps prevent the spread of many viruses, including RSV. Finally, staying up to date on vaccinations and getting a flu shot every year can make a substantial difference in our health and the health of those around us.