Some healthcare experts point to an “immunity gap” tied to the COVID-19 pandemic, while others suggest alternative theories such as temporary immunodeficiency brought on by COVID-19. In most cases, RSV causes “mild, cold-like symptoms,” but the CDC states it also can cause serious illness, especially for infants, young children, and older adults, leading to emergency room visits, hospitalizations, and an increased demand for clinical laboratory testing.
Pulmonology Advisor reported that the disease typically peaks between December and February, but hospitalizations this season hit their peak in November with numbers far higher than in previous years. In addition to infants and older adults, children between five and 17 years of age were “being hospitalized far in excess of their numbers in previous seasons,” the publication reported.
“Age by itself is a risk factor for more severe disease, meaning that the younger babies are usually the ones that are sick-sick,” pediatrician Asuncion Mejias, MD, PhD (above), a principal investigator with the Center for Vaccines and Immunity at Nationwide Children’s Hospital in Columbus, Ohio, told MarketWatch. Now, she added, “we are also seeing older kids, probably because they were not exposed to RSV the previous season.” Clinical laboratories in hospitals caught the brunt of those RSV inpatient admissions. (Photo copyright: Nationwide Children’s Hospital.)
Did COVID-19 Cause Immunity Gap and Surge in Respiratory Diseases?
CDC data shows that hospitalization rates linked to RSV have steadily declined since hitting their peak of 5.2 per 100,000 people in mid-November. In contrast, hospitalizations linked to the flu peaked in late November and early December at 8.7 per 100,000. Hospitalizations linked to COVID 19—which still exceed those of the other respiratory diseases—reached a plateau of 9.7 per 100,000 in early December, then saw an uptick later that month before declining in the early part of January, 2023, according to the CDC’s Respiratory Virus Hospitalization Surveillance Network (RESP-NET) dashboard.
Surveillance by the CDC’s National Center for Immunization and Respiratory Diseases (NCIRD) revealed a similar pattern: An early peak in weekly numbers for emergency room visits for RSV, followed by a spike for influenza and steadier numbers for COVID-19.
So, why was the RSV outbreak so severe?
Respiratory diseases tend to hit hardest in winter months when people are more likely to gather indoors. Beyond that, some experts have cited social distancing and masking requirements imposed in 2020 and 2021 to limit the spread of COVID 19. These measures, along with school closures, had the side effect of reducing exposure to influenza and RSV.
“It’s what’s being referred to as this ‘immunity gap’ that people have experienced from not having been exposed to our typical respiratory viruses for the last couple of years, combined with reintroduction to indoor gatherings, indoor venues, indoor school, and day care without any of the mitigation measures that we had in place for the last couple of years,” infectious disease expert Kristin Moffitt, MD, of Boston Children’s Hospital told NPR.
Term ‘Immunity Debt’ Sparks Controversy
Other experts have pushed back against the notion that pandemic-related public health measures are largely to blame for the RSV upsurge. Many have objected to the term “immunity debt,” a term Forbes reported on in November.
“Immunity debt is a made-up term that did not exist until last year,” pediatrician Dave Stukus, MD, wrote on Twitter. Stukus is a Professor of Clinical Pediatrics in the Division of Allergy and Immunology at Nationwide Children’s Hospital in Columbus, Ohio.
An article published by Texas Public Radio (TPR) suggests further grounds for skepticism, stating that “the immunity debt theory doesn’t seem to hold up to scrutiny.”
“That was sort of the great unmasking, and everybody got viral illnesses,” she told TPR. “Now we’re past that. We’ve already been through that. We should have some immunity from that and we’re having it again.”
She added that “the hospital is filled with babies who are less than a year of age who have RSV infection. Those children weren’t locked down in 2020.”
The story also noted that not all Americans complied with social distancing or masking guidelines.
“We’re not seeing [less viral illness in] states in the United States that were less strict compared to states that were stricter during mask mandates and things like that. All the states are being impacted,” Barton told TPR.
Perfect Storm of Demand for Clinical Laboratory Testing
Barton suggested that COVID-19 might have compromised people’s immune systems in ways that made them more susceptible to other respiratory diseases. For example, a study published in Nature Immunology, titled, “Immunological Dysfunction Persists for Eight Months following Initial Mild-to-Moderate SARS-CoV-2 Infection,” found that some patients who survived COVID-19 infection developed post-acute long COVID (LC, aka, COVID syndrome) which lasted longer than 12 weeks. And that “patients with LC had highly activated innate immune cells, lacked naive T and naive B cells, and showed elevated expression of type I IFN (IFN-β) and type III IFN (IFN-λ1) that remained persistently high at eight months after infection.”
Experts speaking to The Boston Globe said that multiple factors are likely to blame for the severity and early arrival of the RSV outbreak. Pediatric hospitalist and infectious disease specialist Chadi El Saleeby, MD, of Massachusetts General Hospital, said the severity of some cases might be tied to simultaneous infection with multiple viruses.
Clinical laboratories experienced a perfect storm of infectious disease testing demands during this tripledemic. Hopefully, with the arrival of spring and summer, that demand for lab tests will wane and allow for a return to a normal rate of traditional laboratory testing.
Experts advise clinical laboratories to prepare now for a marked increase in demand for RSV, COVID-19, and influenza testing
Are the COVID-19 lockdowns responsible for the increase in cases of respiratory syncytial virus (RSV)? Some physicians believe that may be the case and it has hospitals, clinical laboratories, and pathology groups scrambling to prepare for a possible “tripledemic,” according to UC Davis Health.
The addition of RSV as we move into what is predicted to be a bad influenza (flu) season has prompted the Centers for Disease Control and Prevention (CDC) to issue a Health Alert Network (HAN) advisory which states, “Co-circulation of respiratory syncytial virus (RSV), influenza viruses, SARS-CoV-2, and others could place stress on healthcare systems this fall and winter.” This is especially true of clinical laboratories that still struggle to keep pace with demand for COVID-19 testing.
“COVID cases are expected to rise during the winter. This will be occurring at the same time we expect to see influenza rates increase while we are already seeing an early start to RSV season,” said Dean Blumberg, MD (above), chief of pediatric infectious diseases at UC Davis Children’s Hospital. “With all three viruses on the rise, we are worried about an increase in the rates of viral infection that may lead to an increase in hospitalizations.” Clinical laboratories should prepare for a marked increase in demand for RSV testing, as well as COVID-19 and influenza. (Photo copyright: UC Davis Health.)
Masking, Lockdowns, and Social Distancing Could be Responsible
Every winter in the United States, outbreaks of the flu and RSV occur. However, this year the RSV outbreak appears to be more serious. The CDC warns that “surveillance has shown an increase in RSV detections and RSV-associated emergency department visits and hospitalizations in multiple US regions, with some regions nearing seasonal peak levels.”
The current spread of RSV infections taking place in the US varies from prior outbreaks in notable ways:
Incidents are happening in the fall, whereas RSV outbreaks usually peak starting in late December.
Older children as well as infants are being hospitalized.
Current cases appear to be more severe.
Episodes are rising at a time when pediatric hospitalizations are already higher than usual due to other illnesses like COVID-19, influenza, and biennial enteroviruses.
Some experts believe that masking and social distancing due to the COVID-19 pandemic resulted in a respite of RSV infections in 2020. However, cases intensified in 2021, most likely a result of fewer young children being exposed to RSV during the previous year.
Most children typically have had at least one RSV infection before the age of two and the illness becomes less troublesome as children get older.
“The theory is that everyone’s now back together and this is a rebound phenomenon,” Jeffrey Kline, MD, Associate Chair of Research, Wayne State University School of Medicine in Detroit, told MarketWatch. “If we think about the relative increase—ninefold increase—that’s not nothing, especially in the pediatric [emergency departments]. Holy mackerel.”
Most RSV Infected Children Require Hospitalization
Kline is in charge of a surveillance network that aggregates information regarding incidents of viral infections from 70 US hospitals. The data shows that more children are being hospitalized with COVID-19 than with RSV, but that 5% of children are testing positive for both illnesses. About 60% of children in that group require hospitalization.
According to the CDC, individuals with RSV will typically begin to experience symptoms within four to six days after getting infected. Symptoms of RSV, which tend to appear in stages, include:
Runny nose
Decrease in appetite
Coughing
Sneezing
Fever
Wheezing
“RSV causes a mild cold illness in most people. But it can be very dangerous for very young children and older adults. And young infants are usually the most at risk of hospitalizations in what physicians would call their first RSV season,” said Andrea Garcia, JD, Vice President, Medicine and Public Health, American Medical Association (AMA), in a November 2 AMA update on the current flu season.
“In a pre-pandemic year,” she added, “we would see 1% to 2% of babies younger than six months with an RSV infection maybe needing to be hospitalized. And virtually all children have gotten an RSV infection by the time they’re two-years-old.”
Infants are at a much higher risk of experiencing severe disease due to RSV because their immune systems are not fully developed, and those under six months old are unable to breathe through their mouths if they are congested.
Mejias is studying whether prior exposure to COVID-19 alters how a baby’s immune system reacts to RSV, and if it may lead to more severe illness in those babies.
“That is something to work on and understand,” she said.
Comorbidities and Compromised Immune Systems also a Factor
Older adults and adults with weakened immune systems are predisposed to RSV infections, but there are things people can do to mitigate their chances of becoming ill from RSV.
“[RSV] is spread through contact with droplets from the nose and throat of infected people when they cough or sneeze. It can also be spread through respiratory secretions on surfaces,” said Garcia in the AMA update. “So, it’s a really good idea to clean and disinfect surfaces, especially in areas where young children are constantly touching things. Handwashing is always important. And if you are sick, please stay home.”
She added, “Premature infants, children with certain medical conditions, are also eligible to take a monthly monoclonal antibody treatment during RSV season, and that can help them stay out of the hospital.”
Most RSV infections typically go away on their own within a week or two. But such infections can lead to more severe illnesses, such as bronchiolitis and pneumonia. The more serious cases may require hospitalization with additional oxygen, IV fluids, and even intubation with mechanical ventilation. In most cases, hospitalization only lasts a few days, according to the CDC.
Be Prepared for a Tripledemic
“Health officials are concerned that this could be a sign of what’s to come,” stated Garcia in the AMA update. “A difficult winter, with multiple respiratory viruses circulating.”
For clinical laboratory managers, the early arrival of RSV cases at the front end of this influenza season provides an opportunity to position their labs to better meet the demand for RSV testing. They should also advise their client physicians that there may be a surge of respiratory illnesses during this flu season.
