All about RSV, the virus responsible for the bronchiolitis epidemic

This year, the bronchiolitis epidemic is affecting pediatric services earlier and more strongly, which has prompted the government to trigger a health emergency plan. Biological explanations on this virus of the lower respiratory tract which mainly infects infants.

The bronchiolitisbronchiolitis is a viral infection that affects the lower respiratory tract of 30% of children under two years of age each year. the virusvirus respiratory syncytial (or RSV) is responsible for it in nearly 80% of cases, even if other viruses can be the cause (rhinovirus, adenovirus, influenza virus, enterovirus, etc.).

Viral family and mechanism of infection

Unlike most living things that carry genetic information on a double-stranded DNA molecule, RSV is an “RNA” virus that stores its genetic material on a single-stranded RNA molecule. The RNA is wrapped in a nucleoprotein which plays a crucial role in transmitting the virus to an individual.

As a reminder, when a virus enters cells (lung cells here), it hijacks the host’s cellular machinery to produce a large number of new copies of the virus. These can then infect other cells or be transmitted to another individual. The nucleoprotein envelope protects the viral RNA from the host’s immune defenses and contributes to its multiplication, by presentation of the RNA to the viral enzyme which copies it.

In order to better understand how the virus multiplies in the infected cell, researchers have studied the three-dimensional structure of this complex formed by RNA and nucleoprotein in a previous study. In detail, the nucleoproteins associate with each other throughout the RNA, forming a chain. Each nucleoprotein is made up of two domains that enclose the RNA (like a clamp). The researchers’ hypothesis is that, during viral multiplication, the clamp opens to let through only the enzyme that reads the genetic information of the RNA sequence. The viral RNA would thus always be protected within the complex.

Why infants?

While adults can be affected by bronchiolitis (asymptomatically), the disease is much more commonly seen in infants under 6 months of age. The reason would be on the side of the immune defenses according to a team from the Institut Pasteur. The researchers have identified a population of B lymphocytes that RSV primarily infects, and which would only be present in very young children.

Epidemiological point in France

After the pre-epidemic alert last month in five French regions, it is now the whole country that is affected by theepidemicepidemic of bronchiolitis. In his weekly epidemiological bulletin, Public Health France reports that hospitalizations for bronchiolitis represent 50% of hospitalizations following a visit to the emergency room in children under two years old last week. This percentage was around 40% during the peaks of previous seasons.

Yesterday, the government announced the triggering of a national emergency plan, planned for exceptional health situations. Indeed, AFP indicates that the ” number of visits to the emergency room and hospitalizations for bronchiolitis is very high, and at levels higher than those observed at epidemic peaks for more than 10 years ! In this period of hospital crisis, this trigger allows the entire hospital to focus on this particular problem.

Bronchiolitis: 5 regions on pre-epidemic alert in mainland France

Article by Julie Kern, published on October 6, 2022

All the winterswinters, the bronchiolitis virus infects nearly 500,000 infants under the age of two. Since the end of September, the epidemic has been slowly waking up in France: five regions are on “orange vigilance”.

As winter approaches, Public Health France monitors the circulation of the respiratory syncytial virus, RSV, the main cause of infant bronchiolitis, a respiratory disease that affects 30% of children under two years old each year, i.e. 480,000 annual cases. At the beginning of October, five regions of metropolitan France are already in the pre-epidemic phase: Hauts-de-France, Ile-de-France, New Aquitaine, Occitanie and Normandy, on alert for already half a year. -september.

The pre-epidemic alert testifies to the rapid increase in cases of bronchiolitis for several weeks, without this exceeding the epidemic thresholdepidemic threshold. Figures from Public Health France show that hospitalizations for bronchiolitis increased by 41% between week 38 and week 39. Of the 1,491 infants admitted to the emergency department for symptomssymptoms of bronchiolitis, 456 had to be hospitalized – an increase of 27% compared to week 38. The actions of SOS Médecin to manage bronchiolitis also jumped by 28%.

The current data follows the evolution of the epidemic in the winter of 2021-2022, when Covid-19 was also circulating. On the other hand, if we compare to the 2019-2020 epidemic, the one observed today is six weeks ahead. On the contrary, the 2020-2021 epidemic was very late, with a peak only reached in January 2021, due to the pronounced confinement at the end of October 2020.

Bronchiolitis, a virus that comes back every winter

Infantile bronchiolitis is a viral respiratory disease caused by a virus very contagiouscontagious, RSV. It spreads easily from person to person via the salivasaliva, sneezing or coughing; but also by contaminated surfaces. An infected baby initially shows symptoms of a cold, accompanied by a mild cough. As the infection progresses, the cough intensifies and the breathing becomes wheezy; fever may appear. The child sleeps poorly and has difficulty feeding.

The disease resolves spontaneously in five to ten days, but the cough can last several weeks. In some children, wheezing can worsen into respiratory distress. Hospital treatment is then required. Recurrent bronchiolitis also exposes infants to increased risk of bacterial superinfection. Finally, premature babies require increased vigilance. The disease requires hospitalization in 2 to 3% of cases, it is fatal in less than 1% of cases.

Bronchiolitis and baby: how to protect your infant?

A Sanofi vaccine in the making

In all cases, a doctor or pediatrician should be consulted when symptoms appear to confirm the diagnosis and adapt treatment to the child. September 16, 2022Sanofi has received support from the European Medicines Agency for the authorization of its RSV bronchiolitis vaccine, Beyfortus®, jointly developed with Astra-Zeneca. According to data fromclinical studiesclinical studies, it protects against severe forms of bronchiolitis, those that require hospitalization. Single dose vaccine and said to be passive because immunization is based on the action of a antibodyantibody therapy – nirsevimab – to neutralize the virus. It is intended to replace the Synagis currently available. In either case, these vaccines are recommended for premature babies or infants at risk such as those with congenital cardiomyopathy, but not for all children under 2 years of age.

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