Respiratory Diseases Roundup

Influenza Deaths Surpass COVID-19, Emerging Variants, and Viral Risks

Miranda Manier, BA

Influenza Deaths Surpass COVID-19 Mortality for the First Time Since Pandemic Onset1

Recent data from the CDC indicate that influenza deaths exceeded COVID-19 deaths in the United States for the first time since the pandemic began. For the week ending January 25, 1.7% of all deaths nationwide were attributed to influenza, compared with 1.5% from COVID-19. Influenza-related hospitalizations were more than three times higher than those for COVID-19 amid a record influenza season. The most significant disparities were observed in California, Hawaii, Washington, Oregon, and Wyoming, where influenza-related deaths were at least double those of COVID-19.

This winter's influenza season has seen one of the highest infection rates since the 2009 H1N1 pandemic. CDC estimates suggest between 13,000 and 65,000 influenza-related deaths have already occurred, surpassing last season's totals. In contrast, COVID-19 deaths are estimated between 18,000 and 31,000 for the winter. Despite relatively high COVID-19 vaccination rates among adults older than 65 years of age, influenza vaccination uptake has declined, particularly among children, with rates falling from 58% in 2020 to under 45% this season. Health officials emphasize the importance of influenza vaccination to curb severe illness and mortality as activity remains elevated in 33 states and the District of Columbia.

Emergence and Spread of LP.8.1 SARS-CoV-2 Variant2

A new SARS-CoV-2 variant, LP.8.1, a descendant of the JN.1 lineage, is emerging globally, particularly in Canada, the United States, Japan, and Australia. LP.8.1 has nine additional spike protein mutations compared to JN.1, and eight distinct mutations relative to XEC, the previously dominant variant. Epidemiological modeling estimates LP.8.1 has a slightly higher effective reproduction number than XEC, at 1.067 in the United States, but with smaller differences in Japan (1.019). The variant’s spread suggests it may have a competitive advantage in certain regions, potentially influenced by population immunity from prior infections and vaccinations.

Laboratory analysis of LP.8.1 pseudoviruses indicates that its infectivity is significantly lower than that of JN.1, while maintaining higher immune resistance similar to XEC and KP.3.1.1. Specific spike protein mutations, including Ser31del and Phe186Leu, were found to increase infectivity, whereas His445Arg and Phe456Leu reduced it. Neutralization assays with sera from JN.1 and KP.3.3-infected individuals and those vaccinated with a JN.1-based mRNA vaccine showed comparable immune evasion between LP.8.1, XEC, and KP.3.1.1. Further real-world epidemiological data are needed to determine LP.8.1’s potential impact on transmission and vaccine efficacy across different populations.

Changing Patterns in SARS-CoV-2 Reinfection Risk Post-Omicron3

A recent epidemiological study examines shifts in SARS-CoV-2 reinfection risk before and after the emergence of the omicron variant. Prior to omicron, natural infection conferred durable and long-lasting protection against reinfection, with minimal decline over time. However, in the omicron era, protection waned quickly, diminishing within a year. These findings highlight a fundamental shift in SARS-CoV-2 immune dynamics, with viral evolution increasingly favoring immune escape rather than intrinsic transmissibility.

This shift suggests that SARS-CoV-2 is adapting to evade prior immunity, altering reinfection patterns and underscoring the need for periodic vaccine updates. The study highlights the importance of ongoing surveillance and booster immunization strategies to counteract declining immunity. These findings contribute to a broader understanding of how SARS-CoV-2 continues to evolve, reinforcing the role of updated vaccines in maintaining protection against emerging variants.

Cardiovascular Complications in Pediatric Respiratory Virus Hospitalizations4

A cross-sectional analysis of hospitalized children and young adults (≤ 20 years) from 2020 to 2021 compared cardiovascular complications associated with COVID-19, influenza, and respiratory syncytial virus (RSV). Among 212,655 respiratory virus hospitalizations, myocarditis was more common in COVID-19 cases (0.9%) than in influenza (0.2%) and RSV (0.1%). Adjusted analysis showed a 61% lower risk of myocarditis in influenza cases and an 85% lower risk in RSV cases compared with COVID-19. Bradyarrhythmias and heart block were also more frequent in COVID-19 (0.8%) compared to influenza (0.5%) and RSV (0.2%), with RSV cases exhibiting a 49% lower adjusted risk.

No significant differences were observed in the rates of tachyarrhythmias, sudden cardiac arrest, or in-hospital mortality between the three viruses after adjusting for confounders. The findings indicate that COVID-19 carries a higher risk of cardiovascular complications in children and young adults compared to influenza and RSV, emphasizing the need for heightened clinical vigilance, preventive measures, and timely treatment to mitigate severe outcomes.

References

  1. Tin A. Flu deaths may have surpassed COVID deaths nationwide for first time since start of pandemic, early CDC data suggests. CBS News. Updated on February 11, 2025. Accessed February 27, 2025. https://www.cbsnews.com/news/flu-deaths-surpass-covid-for-first-time-since-pandemic-started/
  2. Chen L, Kaku Y, Okumura K, et al. Virological characteristics of the SARS-CoV-2 LP.8.1 variant. Lancet Infect Dis. 2025:S1473-3099(25)00079-9. doi:10.1016/S1473-3099(25)00079-9
  3. Chemaitelly H, Ayoub HH, Coyle P, et al. Differential protection against SARS-CoV-2 reinfection pre- and post-Omicron. Nature. Published online February 5, 2025. doi:10.1038/s41586-024-08511-9
  4. Khanal S, Khanal B, Chou FS, Moon-Grady AJ, Ghimire LV. Comparison of mortality and cardiovascular complications due to COVID-19, RSV, and influenza in hospitalized children and young adults. BMC Cardiovasc Disord. 2024;24(1):686. doi:10.1186/s12872-024-04366-0