On behalf of the TeamHealth Emerging Infectious Disease Task Force
Respiratory viruses – primarily COVID-19, Influenza, and RSV are having an impact as winter conditions enhance communicability. Elevated numbers of cases and admissions for all three of these viruses were reported at the beginning of this year. The severity of the clinical impacts varies from region to region based on immunization density, environmental conditions, and public health behaviors. In this article, the TeamHealth Emerging Infectious Disease Taskforce addresses questions related to these three illnesses.
SARS-CoV-2
SARS-CoV-2 continues to evolve into different variants with different infectious characteristics. This year, all major variants continue to be from the Omicron lineage. The current JN.1 variant accounts for 93.1% of all SARS-CoV-2 cases serotyped by the CDC. More variants will continue to emerge which always raises the concern that the evolving virus will have the potential to promote more severe disease.
The most recent data demonstrates that new COVID-19 related hospital admissions surge peaked on January 6 at 34,909 admits.
- As of February 3
- New admissions had declined by 40.50% to 20,772.
- Admissions accounted for 2.9% of inpatient beds (decline of 25.6%) and 2.7% (decline of 20.5%) of critical care beds. There is also a congruent decline in overall COVID-19 related emergency department encounters.
- Reported ED encounters during this surge peaked on December 24 of 2023 at 3.48%.
- As of February 8
- The percent of ED encounters declined by 52% to 1.67%. (The CDC data lags behind reality by about one to two weeks.)
Reports currently clearly demonstrate a decline of COVID-19 cases back to previous lower baseline levels. In the past few years, we have seen two main patterns with winter surges of COVID-19. We are currently unsure of which path this surge will take.
Case fatality rates (CFR) are still running at around 3.6% for all cases with almost all of the fatalities being in elderly individuals or those with co-morbid factors.
The enhanced updated COVID-19 vaccines are the most effective way of preventing COVID-19 cases and complications. In addition, positive COVID-19 tests and early diagnoses are important due to the availability of Paxlovid therapy in the over-50 age range.
Influenza
Influenza cases are estimated by Influenza like illness (ILI) seen in outpatient settings – may be settling into a pattern consistent with pre-pandemic years. Essentially all the influenza cases typed are Influenza A.
At week 52 of the 2023-2024 season, outpatient visits peaked at 6.9% above the epidemic threshold of 2.9%. This was the highest since the 2019-2020 season that peaked at 7.1%. That season also started a few weeks earlier than this year. ILI cases declined from there to about 4.28139% on week 4. However, a recent upswing has been noted of 2.7% to 4.39705% during week 6. That is a small overall change, but second seasonal surges are not uncommon.
Effective vaccines are available and are still recommended. In addition, osetamivir is available for active cases and has been noted to have efficacy against current influenza strains.
Respiratory Syncytial Virus (RSV)
Respiratory syncytial virus (RSV) is increasingly recognized as an important cause of severe respiratory disease, not only in children but in older adults.
In the United States
- Up to 160,000 hospitalizations and 10,000 deaths occur annually due to RSV in adults ≥65 years of age.
- Approximately 40,000 infants <5 years of age are hospitalized each year. The estimated RSV mortality rate for infants <1 year old is 3.1 to 5.4 per 100,000 infants. Mortality rates are progressively lower for older children.
Data provided by the CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) provides the best available surveillance on this virus. RSV cases have again tracked with a seasonal surge that is now declining. Again, although this virus is itself a significant infection – it is likely having an additive impact on hospitalizations and respiratory mortality as a co-infection with COVID-19 and influenza.
Although there are no effective antivirals, there are two safe and effective vaccines, Areaxvy® (GSK) and Abrysvo® (Pfizer). The vaccines are indicated for adults aged 60 and older – particularly with co-morbid conditions.
Other Emerging Threats – Mpox
In December 2023, the CDC released a health alert notification regarding a severe Mpox (previously known as Monkey Pox) outbreak within the Democratic Republic of the Congo (DRC). This current Mpox event differs from the 2022-2023 Global Mpox outbreak as it is due to a Clade I Mpox virus with an enhanced human to human transmission, more serious disease and higher mortality.
In the United States, there have been approximately 31,567 confirmed cases of the first (Clade II) Mpox virus with 55 (CFR 0.17) fatalities. As of the time of this post, no known Clade I Mpox infections have been detected in the United States.
The CDC has alerted clinicians to be particularly aware of any patients meeting the clinical criteria for suspected Mpox infection. In addition, any suspected Mpox cases with an epidemiologic connection to the DRC or individuals from the DRC within the last 21 days of detection should have a consultation with local public health authorities and/or the CDC.
Two vaccines are available in the United States under an Emergency Use Authorization from the CDC. These are the JYNNEOS® and ACAM2000® products. Although developed for the Orthopox virus, Smallpox, these vaccines are both effective against Clade I and II Mpox viruses.
Summary
As time passes, infections agents – particularly viral agents – continue to evolve and impact human populations. As the SARS-CoV-2 virus continues to find its place in human populations, we can expect varying levels of unpredictability in its clinical impacts. This makes anticipating upcoming seasonal impacts more difficult. Vigilance, collaboration of medical and public health professionals, education, and understanding are needed as we proceed into the future.
Learn more about TeamHealth’s Emerging Infectious Disease Taskforce (EIDT) and see a full list of references here.