RSV: Virus that threatens infants again circulating in 2022

RSV: Virus that threatens infants again circulating in 2022In South Africa, it is estimated that between 178 000 and 443 000 children under the age of five will be infected with RSV annually. PHOTO: Black Star/Spotlight
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According to the United States National Institutes of Health, Respiratory Syncytial Virus (RSV) is estimated to affect 64 million people around the world every year and claim around 160 000 lives. Infants are most vulnerable and there is no effective vaccine.

In South Africa, it is estimated that between 178 000 and 443 000 children under the age of five will be infected with RSV annually. Numbers were, however, dramatically lower in 2020 and 2021 due to the COVID-19 pandemic and associated restrictions – although substantial increases were correctly predicted for 2022.

RSV is the most common cause of lower respiratory tract infections (LRTI) in young children globally and in South Africa, says Professor Cheryl Cohen, head of the Centre for Respiratory Diseases and Meningitis at the National Institute of Communicable Diseases (NICD). LRTI, in turn, she says, is among the most common causes of death in young children in South Africa.

“Before COVID, we estimate that each year RSV caused 44615 (32731-57538) hospitalisations and 490 (364-720) deaths in children aged <5 years each year. For those aged between a year and four years, there are 52 (25-66) deaths annually,” says Cohen, adding this is much more than COVID.

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What is RSV?

RSV is a well-known respiratory virus, explains Professor Mark Cotton, Head of the Division of Paediatric Infectious Diseases at Stellenbosch University’s Faculty of Medicine and Health Sciences. He says the virus, first isolated in 1956, has some very stable parts that do not change over time. “It causes respiratory infections in children, [the] elderly, and immunocompromised adults, recently recognised as vulnerable,” he says.

Scanning electron micrograph of human respiratory syncytial virus (RSV) virions (colorized blue) and labeled with anti-RSV F protein/gold antibodies (colorized yellow) shedding from the surface of human lung epithelial A549 cells.
Scanning electron micrograph of human respiratory syncytial virus (RSV) virions (colorized blue) and labeled with anti-RSV F protein/gold antibodies (colorized yellow) shedding from the surface of human lung epithelial A549 cells. IMAGE: NIH

Professor Heather Zar, Chair of the Department of Paediatrics and Child Health at Red Cross Children’s Hospital and Director of the SA-MRC Unit on Child and Adolescent Health at the University of Cape Town, explains that RSV can cause symptoms like a cold, but can also cause more severe illness with wheezing or pneumonia.

“Infants, especially under six months of age, children with underlying chronic illness (like chronic lung conditions or heart disease, immunodeficiency), or infants born prematurely are at greatest risk of developing severe disease,” Zar tells Spotlight.

RSV is spread by infected droplets produced when coughing, sneezing, or kissing. It can also be spread by touching surfaces contaminated with the virus and then touching your eyes, nose, or mouth. Children are often exposed to the virus at school. Someone with RSV infection is typically contagious for three to eight days. It can take weeks to recover. 

Changing patterns due to COVID-19

RSV usually has a distinct seasonal pattern, starting in autumn through winter, although this has changed during the COVID-19 pandemic, Zar said during a recent webinar hosted by the South African Paediatric Association.

The (NICD) states that before the COVID-19 pandemic, the RSV season in South Africa usually preceded the influenza season with the usual average onset at the end of February (range from early February – mid-March) over the last ten years. While this pattern was disrupted in 2020 and 2021, it resumed in 2022, with onset in mid-February.

“It disappeared for large periods of 2020, and then [we] saw less in 2021- probably due to all the non-pharmacological interventions like wearing of masks, closing schools, public places among others,” she says. “Now we are experiencing a big RSV season,” Zar told Spotlight. “Partly as infants last year didn’t really experience RSV, so they didn’t develop immunity to this. Modelling studies suggest that we will see a third increase in RSV cases in children compared to the pre-pandemic and that the age group will shift to a slightly older age group with more children aged six months to two years affected.”

Cohen explains that the NICD conducted a mathematical modelling study at the end of last year to predict the 2022 RSV season. She says they were concerned that the immunity gap created over the last two years would lead to an unusually severe RSV season.

“We projected [an] overall 32% increase in [the] number of monthly hospitalisations compared to the average for 2015-2019. The largest percent increase in hospitalisations is projected among older age groups. While zero to two months continue to make up a large proportion of the predicted burden, our projections show a 26, 31, and 36% increase in peak hospitalisations for the three to five months, six to 11, and 11 to 23-month age groups respectively,” says Cohen.

“Following a year of 2020 where there was no RSV circulation, we started to see already in 2021 a shift to older children. We know that RSV hospitalisations predominately occur really in the youngest children. We don’t know entirely to what extent that very young age distribution is influenced by the fact that infants have an intrinsic susceptibility to severe diseases or how much is driven by the fact that attack rates are very high so infants get exposed earlier on in life,” she says, adding that the fact that they started to see this shift to slightly older children suggests that some of the severity is in fact influenced by prior immunity although certainly a big part of it is also affected by intrinsic severity.

She says what they predicated through their modelling was an intense season, slightly early starting [and] peaking in April. This prediction seems quite accurate – the most recent NICD Weekly Respiratory Pathogens Surveillance Report indicates that this year’s RSV numbers have been declining since the first week of May.

Tests, treatments, and vaccines

Much like COVID-19, RSV can be detected by taking samples from the nose and testing for genetic material using a PCR or rapid antigen test. In public hospitals, they use the PCR test.

Cotton explains that people hospitalised with severe symptoms are typically treated with oxygen and provided with adequate hydration. Some antivirals are under development but not yet ready for widespread use. Cotton says that the monoclonal antibody is protective, last a long time, and is very useful, especially in premature babies, for preventing disease. However, current monoclonal antibody prevention has to be given monthly as an injection through the RSV season and is very costly.

There is currently no proven vaccine to prevent RSV infection, hospitalisation or death, but several promising vaccine candidates are under development. “Our studies show that a vaccine would likely be cost-effective for South Africa and may even be cost-saving because RSV is so common,” says Cohen. “So we would hope that when these products become licensed in South Africa, there will be discussion around introducing them.”

Zar explains that there are two promising new strategies, a vaccine given to pregnant women to protect their infants and a long-acting monoclonal antibody given to babies that prevent RSV disease for months – it reduces RSV illness and hospitalisation by 70 to 80% in trials.

“So the future is looking very promising – we need to ensure that these interventions are available and affordable in low and middle-income countries once they are approved,” she says.