Increase in RSV infections is a possible side effect of last year's lockdown

Increasingly, we are hearing that it is not COVID-19 that is the biggest concern for pediatric hospitals today, but the epidemic of RSV infections. Are RSV infections really on the rise and are there more of these infections than in past years?

There is indeed an increase in the incidence of infections caused by RSV. Just look at pediatric wards, where among children hospitalized with symptoms of respiratory tract infections, as many as 70-80 percent, and sometimes even 100 percent, are infected with RSV. It should be noted, however, that for us specialists, this is not surprising. The virus has been well known to us for years. It was discovered and first described in 1956. We know that infections caused by it are common.  This is evidenced, among other things, by data from the United States and Europe. Based on them, it is estimated that up to 34 million children under the age of 5 contract RSV infection each year. It causes 3 million hospitalizations and about 50,000 deaths in this age group (the latter occurring mainly in developing countries).

Why are there more RSV infections this year, did the COVID-19 pandemic have any effect on this?

Definitely yes. We are currently experiencing what is called a compensatory epidemic. RSV infections are seasonal in nature. Increased incidence is seen every year, during the fall and winter season, usually from November to late April. However, last year we had a lockdown. For a long time, nurseries and kindergartens were closed. This means that many children did not come into contact with RSV last season. So there are more of them susceptible this year and as a result we are seeing an increase in infections.

Let us remind - how can you get infected with it and what symptoms does it cause?

Sources of infection are sick people. The virus is most often transmitted through droplets, e.g. when coughing or sneezing. But it can also be transmitted by contact. This happens when certain surfaces are contaminated with secretions from the patient's respiratory tract. In the case of children, such contaminated surfaces are often toys.
In terms of symptoms, the first phase of RSV infection is just like the common cold. There is dry cough, runny nose, low-grade fever. In a significant percentage of patients, these symptoms end because the infection is self-limiting. Unfortunately, there are also patients who become more seriously ill and require hospital treatment. It  is necessary when coughing gets worse and difficult to expectorate secretions remain in the bronchial tree. Shortness of breath and difficulty in breathing occur. The youngest children may experience apnea, or pauses in breathing that last 15-20 seconds. Symptoms such as intercostal tightening, movement of the wings of the nose, bruising of the skin, and bruising around the mouth are also signs of increased respiratory effort.

Who is particularly vulnerable to such a severe course of infection?

The youngest patients. Most severe infections requiring hospitalization occur in children from 2 to 6 months of age. Premature babies who have immature respiratory and immune systems are especially at risk. RSV infection can also be dangerous for young patients with bronchopulmonary dysplasia.
We are primarily talking about children here, but it is worth noting that adults also get sick from RSV. People with chronic respiratory diseases, heart defects, transplant patients, patients under immunosuppression (congenital or related to e.g. oncological treatment) are at risk of a severe course of the disease. It is also important to remember people over 65. They, along with the youngest children, are the second group in whom RSV infections can be severe. This is evidenced by the epidemiological facts. It has been estimated that 177,000 seniors in the United States are hospitalized with RSV annually, and 14,000 die from it. These are big numbers that prove RS infections are common and the pathogen itself ubiquitous.

The epidemiological data you mention are mainly from hospitals. Primary care clinics, where parents take their sick children, are unlikely to test for RSV.

However, such diagnostics are available. I am referring to rapid diagnostic tests to detect RSV infection, where the test material is a nasal swab or nasopharyngeal swab. Similarly, we have rapid diagnostic tests for influenza virus infections (types A and B) and tests to detect SARS-CoV-2 coronavirus antibodies. These tests are easy to conduct and the result is obtained within several minutes. However, they are indeed too rarely used in primary care clinics, mainly for financial reasons. More often these tests, as well as other tests to determine the etiology of the disease, are performed in hospitals. Undoubtedly, however, we can speak of an epidemiological iceberg phenomenon. The infections we recognize and then report are just the tip of it. This means that the extent of the disease is much greater than official reports indicate. This is true not only for RSV infections, but also for influenza or COVID-19.

While we're on the subject of COVID-19. Can you distinguish between symptoms of coronavirus infection and symptoms of RSV infection?

It's not easy. I would even say impossible, especially in the early stages of the disease. There are no symptoms typical of an infection caused by RSV, influenza virus, or coronavirus. Suffice it to recall that at the beginning of the pandemic, the loss of smell and taste was thought to be characteristic of COVID-19. At this time, we know that these symptoms are no longer as common. All of these infections are characterized by flu-like symptoms, so it is difficult to make a diagnosis based on symptoms alone.

RSV is spread through contact with droplets, so to reduce the risk of infection we should avoid contact with people who have flu-like symptoms...

Yes, hand hygiene, disinfecting surfaces (including toys), and avoiding exposure to tobacco smoke are also important in prevention of diseases. We have a preventive drug program for babies born prematurely. Under this program, premature infants (after appropriate qualification) receive a humanized monoclonal antibody of IgG class called palivizumab. The preparation is administered by injection from October to the end of April. Five intramuscular injections at monthly intervals are recommended. At least three doses are needed for prophylaxis to be effective.

And is there a chance for an RSV vaccine?

Today we do not yet have a vaccine. There have been numerous attempts to develop it and unfortunately they have proved unsuccessful for many years. Recently, however, there has been a light at the end of the tunnel. In 2019, researchers at the University of Texas discovered that the so-called fusion protein, against which antibodies are supposed to be produced after vaccine administration, exists in two forms (conformations): pre-fusion and post-fusion. If antibodies to the protein are produced before fusion, they reach high protective concentrations. This discovery was used to create a  formulation that is already in phase three clinical trials to determine the vaccine's effectiveness and safety. So there's a good chance that the vaccine will finally arrive - but initially it will be for people over the age of 60-65.
 

Interviewed by Iwona Kołakowska