Comparative incidence and burden of respiratory viruses associated with hospitalization in adults in New York City

BACKGROUND

Although the burden of influenza is well characterized, the burden of community-onset non-influenza respiratory viruses has not been systematically assessed. Understanding the severity and seasonality of non-influenza viruses, including human coronaviruses, will provide a better understanding of the overall disease burden from respiratory viruses that could better inform resource utilization for hospitals and highlight the value of preventative strategies, including vaccines.

METHODS

From October 2017 to September 2019, a retrospective study was performed in a pre-defined catchment area to estimate the population-based incidence of community-onset respiratory viruses associated with hospitalization. Included patients were ≥18 years old, resided in New York City, were hospitalized for ≥24 hours, and had a respiratory virus detected within 3 calendar-days of admission. Disease burden was measured by hospital length of stay (LOS), intensive care unit (ICU) admissions, and in-hospital mortality and compared among those with laboratory-confirmed influenza versus those with laboratory-confirmed non-influenza viruses (human coronaviruses, parainfluenza viruses, respiratory syncytial virus, human metapneumovirus, and adenovirus).

RESULTS

During the study period, 4232 eligible patients were identified of whom 50.9% were ≥65 years of age. For each virus, the population-based incidence was highest for those ≥80 years of age. When compared to those with influenza viruses detected, those with non-influenza respiratory viruses detected (combined) had higher population-based incidence, significantly more ICU admissions, and higher in-house mortality.

CONCLUSIONS

The burden of non-influenza respiratory viruses for hospitalized adults is substantial. Prevention and treatment strategies are needed for non-influenza respiratory viruses, particularly for older adults.

Epidemiology and seasonality of human parainfluenza serotypes 1-3 in Australian children

Background

Parainfluenza viruses are significant contributors to childhood respiratory illness worldwide, although detailed epidemiological studies are lacking. Few recent Australian studies have investigated serotype‐specific PIV epidemiology, and there is a paucity of southern hemisphere PIV reports. We report age‐stratified PIV hospitalisation rates and a mathematical model of PIV seasonality and dynamics in Western Australia (WA).

Methods

We used linked perinatal, hospital admission and laboratory diagnostic data of 469 589 children born in WA between 1996 and 2012. Age‐specific rates of viral testing and PIV detection in hospitalised children were determined using person time‐at‐risk analysis. PIV seasonality was modelled using a compartmental SEIRS model and complex demodulation methods.

Results

From 2000 to 2012, 9% (n = 43 627) of hospitalised children underwent PIV testing, of which 5% (n = 2218) were positive for PIV‐1, 2 or 3. The highest incidence was in children aged 1‐5 months (PIV‐1:62.6 per 100 000 child‐years, PIV‐2:26.3/100 000, PIV‐3:256/100 000), and hospitalisation rates were three times higher for Aboriginal children compared with non‐Aboriginal children overall (IRR: 2.93). PIV‐1 peaked in the autumn of even‐numbered years, and PIV‐3 annually in the spring, whereas PIV‐2 had inconsistent peak timing. Fitting models to the higher incidence serotypes estimated reproduction numbers of 1.24 (PIV‐1) and 1.72 (PIV‐3).

Conclusion

PIV‐1 and 3 are significant contributors towards infant respiratory hospitalisations. Interventions should prioritise children in the first 6 months of life, with respect to the observed autumn PIV‐1 and spring PIV‐3 activity peaks. Continued surveillance of all serotypes and investigation into PIV‐1 and 3 interventions should be prioritised.

An anti-interferon activity shared by paramyxovirus C proteins: inhibition of Toll-like receptor 7/9-dependent alpha interferon induction

Paramyxovirus C protein targets the host interferon (IFN) system for virus immune evasion. To identify its unknown anti-IFN activity, we examined the effect of Sendai virus C protein on activation of the IFN-α promoter via various signaling pathways. This study uncovers a novel ability of C protein to block Toll-like receptor (TLR) 7- and TLR9-dependent IFN-α induction, which is specific to plasmacytoid dendritic cells. C protein interacts with a serine/threonine kinase IKKα and inhibits phosphorylation of IRF7. This anti-IFN activity of C protein is shared across genera of the Paramyxovirinae, and thus appears to play an important role in paramyxovirus immune evasion.

Pneumonias in adults due to mycoplasma, chlamydiae, and viruses

Pneumonias in adults due to mycoplasma, chlamydiae, and viruses are a common clinical problem. These microorganisms contribute to the etiologies in 6-35% of all cases of pneumonia and are the sole pathogens in 1-17% of hospitalized cases. Important trends and developments in the field include the emergence of a Chlamydia psittaci strain (TWAR) that is passaged from human to human, causes a mycoplasma-like illness, and that is relatively resistant to erythromycin, the recognition of respiratory syncytial virus as a pathogen in nursing home outbreaks and in immunosuppressed adults, the continuing high lethality of fully developed influenza pneumonia, the efficacy of acyclovir and adenine arabinoside in limiting the complications of varicella-zoster virus infections, and the increasing frequency of pneumonia caused by cytomegalovirus and the severity of this disorder in highly immunosuppressed patients. Developments in the rapid diagnosis and therapy of respiratory syncytial virus infections with an aerosolized antiviral drug in children may pave the way for comparable advances in difficult pneumonias in adult patients.