Why is Respiratory Syncytial Virus Serious?

Respiratory syncytial virus (RSV) can cause a viral respiratory infection that affects the lungs and respiratory tract in adults and children.

RSV is the leading global cause of respiratory infections in infants and the second most frequent cause of death during the first year of life. This highly contagious seasonal virus is responsible for approximately 3 million hospitalizations and 120,000 deaths annually among children under the age of 5 years.

RSV Proteins

Glycoprotein G is a 298-amino acid RSV large glycoprotein. Glycoprotein G is in involved in attachment to respiratory epithelial cells. In addition to its role in attachment, Glycoprotein G helps RSV evade host immunity.

RSV F is a protein anchored on the viral surface; it mediates viral fusion.

Severe Airway Disease

RSV Nonstructural 2 (NS2) is a contributing factor for the enhanced propensity of RSV to cause severe airway disease in young children. Infection of human cartilaginous airway epithelium with recombinant respiratory viruses revealed that RSV NS2 protein promotes shedding of infected epithelial cells, resulting in two consequences of virus infection. First, epithelial cell shedding accelerated the reduction of virus titers, by clearing virus-infected cells from airway mucosa. Second, epithelial cells shedding into the narrow-diameter bronchiolar airway lumens resulted in rapid accumulation of detached, pleomorphic epithelial cells, leading to acute distal airway obstruction.

The interferon (IFN) system is an important component of host defense against viral pathogens. Viruses exhibit a number of mechanisms that interfere with host IFN response. Viruses exhibit a number of mechanisms that interfere with host IFN response. Some, like influenza A virus and poliovirus, reduce the synthesis of IFN. The NS1 and NS2 proteins of human RSV have been shown to antagonize the type I interferon IFN response.

When is RSV Season?

RSV is a seasonal virus, characterized by variable epidemiology, depending on geographic area and climate. However, this can vary from year to year. Also, the seasonality and severity may vary among different communities. In temperate regions of the Northern hemisphere, virus diffusion generally occurs in the period spanning October/November to March/April, with peak incidence in January/February, which partly overlaps with the influenza virus season.

Restrictive measures for prevention and control of the SARS-COV-2 virus pandemic – especially physical distancing, the use of face masks, and the discontinuation of in-person teaching activities – are likely responsible for the reduced circulation of RSV and other respiratory pathogens during the 2020–2021 season.

Although there are strong seasonal trends, RSV circulation may increase in periods outside the typical seasonality; for example, Australia revealed a higher-than-expected number of cases during the austral spring, from September to December; in contrast, the winter data indicated that RSV circulation was lower than expected.

Risk Factors

A group of risk factors for RSV were associated with acute lower respiratory infection in children under five years. RSV is known to be more likely to have a severe outcome in children with certain pre–existing chronic medical conditions, resulting in higher rate of hospitalization and higher risk of death.

Eight risk factors for RSV (prematurity, low birth weight, being male, siblings, maternal smoking, history of atopy, no breastfeeding and crowding ≥7 persons in household) were observed to be significantly associated with RSV–associated acute lower respiratory infection.

Other risk factors (low parental education, passive smoking, daycare center attendance, indoor air pollution, HIV, multiple births, malnutrition, higher altitude and previous illness) were also observed to have an association with RSV–associated acute lower respiratory infection in some studies.

Transmission

Children may commonly come into contact with RSV at school or daycare centers. They may then pass it on to family members. Close contact, such as kissing, can transmit the virus. Also, if a person with RSV coughs or sneezes, infected droplets can pass on to others. In addition, touching surfaces that contain these droplets, then touching the face can transmit RSV.

Symptoms

People may develop symptoms of the infection 4–6 days after exposure to RSV. These symptoms can include a runny nose, coughing, sneezing, a sore throat, a mild headache, a decreased appetite, a fever, wheezing, rapid breathing, cyanosis, a blue tinge to the skin, irritability and decreased activity. Short, shallow and rapid breathing is common in infants.

Duration

An infection with RSV is usually contagious for around 3–8 days. In infants under 6 months and people with weakened immune systems, the virus may continue to be contagious for up to 4 weeks, even when symptoms are no longer present. People with no underlying medical conditions usually recover within 1 to 2 weeks.

Complications

RSV can cause more serious health problems. Healthy adults and infants infected with RSV do not usually need to be hospitalized. But some people with RSV infection, especially older adults and infants younger than 6 months of age, may need to be hospitalized if they are having trouble breathing or are dehydrated.

Possible complications of RSV include pneumonia, bronchiolitis, a middle ear infection and recurrent RSV infections. Those at highest risk of complications or severe RSV symptoms include young infants, particularly those under 6 months, older adults, particularly those over the age of 65, infants born preterm, children with neuromuscular disorders, adults or children with weakened immune systems and people with congenital heart or chronic lung diseases.

In the most severe cases, a person may require additional oxygen, or IV fluids (if they can’t eat or drink enough), or intubation (have a breathing tube inserted through the mouth and down to the airway) with mechanical ventilation (a machine to help a person breathe). In most of these cases, hospitalization only lasts a few days.

An RSV infection may also worsen certain conditions, including asthma, chronic obstructive pulmonary disease and heart failure.

Prevention

Handwashing: This is important after coming into contact with anyone who has cold-like symptoms and before coming into contact with a child. Regular handwashing can also help children learn its importance.

Keeping surfaces clean: This involves regularly cleaning and disinfecting surfaces that people touch often, such as toys, tabletops, mobile devices, doorknobs and handles.

Coughs and sneezes: Cover the mouth, preferably with a tissue or handkerchief, when coughing or sneezing. Or sneeze into the elbow to avoid spreading infected droplets.

Other tips for prevention include not sharing cups and utensils, limiting contact with people who have cold-like symptoms, limiting time spent in areas where RSV may be especially contagious, such as childcare settings, particularly in the fall, winter and spring.

Keep your hands off your face. Avoid touching your eyes, nose, and mouth with unwashed hands.