Even during the Height of the 2009 Pandemic (Oct) - ILI’s Aren’t Always The Flu
#15,889
When it comes to epidemics, pandemics, and infectious diseases, the past 20 years has shown that conventional wisdom isn't what it used to be. Many of the widely held assumptions from early in the 21st century have been shown to be shortsighted, or even naive.
Twenty years ago, coronaviruses were thought to be relatively benign producers of mild, flu-like illnesses in humans, and incapable of producing a pandemic.
That perception began to change in 2003 - with the SARS epidemic (and the emergence of MERS-CoV in 2012) - but novel influenza remained at the top of most expert's pandemic threats list until COVID-19 emerged roared to life in early 2020.
- Seven years ago conventional wisdom held that Ebola was too virulent, and incapacitated its victims too quickly, to ever spark a regional, multi-national epidemic. It would `burn itself out' before it could spread. Then the West African Outbreak occurred, killing 11,000+ (see Conventional Wisdom And Epidemic Disease Spread).
- Conventional wisdom also said that wild and migratory birds couldn't spread HPAI avian flu viruses across vast distances because `sick birds don't fly' (see WHO: Migratory Birds & The Potential Spread Of Avian Influenza).
- Up until relatively recently, Influenza B was considered to be a `less serious ' health threat than influenza A, a notion belied by a number of studies over the past decade showing the impact of this strain (see ERJ: When “B” becomes “A” : The Emerging Threat of Influenza B Virus).
DOH: 2nd NJ Facility Reporting Adenovirus Outbreak & 10th Fatality At Wanaque Center
Non-influenza Respiratory Viral Infections (NRIVs) are less well studied (and tested for) than influenza, and therefore don't tend to get the same level of respect, yet they produce a high burden of illness, hospitalization, and death each year.
While we have vaccines and antivirals for the `flu', for NRIVs care is mostly supportive while the virus runs its course (note: There is an adenovirus vaccine, but it is only approved for the military).
All of which brings us to a new study, published today in the Canadian Medical Association Journal (CMAJ), which looks at the burden of NRIVs among hospitalized adults across 3 seasons (2015-2018) in Edmonton, Alberta and Toronto, Ontario.
Not only were NRIVs responsible for more than half of all admissions (54.6%), they produced similar rates of illness and deaths to Influenza A.
First a brief press release, followed by a link and the Abstract from the study. Follow the link to read it in its entirety. I'll have a brief postscript when you return.
Noninfluenza viruses have rates of illness, death similar to flu
CANADIAN MEDICAL ASSOCIATION JOURNAL
Noninfluenza respiratory viral infections (NIRV) are associated with illness and death rates similar to influenza in hospitalized adults, according to new research in CMAJ (Canadian Medical Association Journal).
In a study of 2119 adults admitted to two hospitals over three seasons (2015-2018) in Edmonton, Alberta, and Toronto, Ontario, with confirmed viral acute respiratory infections, more than half (54.6%) were NIRV infections compared with influenza viruses (45.4%). Among patients with NIRV infections, 21.1% needed respiratory support, 18.2% required lengthy hospital stays and 8.4% died within 30 days of diagnosis. About 15% of NIRV infections were acquired in hospital.
"These findings show that clinical status changes for patients with NIRV infections were comparable to patients with influenza," writes Dr. Nelson Lee, Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, with coauthors. "The associated costs of hospital admission were substantial."
Patients with NIRV infections were generally younger than those with influenza, although many had underlying conditions, such as compromised immune systems.
"Our findings highlight unmet needs and research gaps in therapeutics and vaccines for people at high risk of NIRV infection," the authors conclude.
Burden of noninfluenza respiratory viral infections in adults admitted to hospital: analysis of a multiyear Canadian surveillance cohort from 2 centres
Nelson Lee, Stephanie Smith, Nathan Zelyas, Scott Klarenbach, Lori Zapernick, Christian Bekking, Helen So, Lily Yip, Graham Tipples, Geoff Taylor and Samira Mubareka
CMAJ March 29, 2021 193 (13) E439-E446; DOI: https://doi.org/10.1503/cmaj.201748
Abstract
BACKGROUND: Data on the outcomes of noninfluenza respiratory virus (NIRV) infections among hospitalized adults are lacking. We aimed to study the burden, severity and outcomes of NIRV infections in this population.
METHODS: We analyzed pooled patient data from 2 hospital-based respiratory virus surveillance cohorts in 2 regions of Canada during 3 consecutive seasons (2015/16, 2016/17, 2017/18; n = 2119). We included patients aged ≥ 18 years who developed influenza-like illness or pneumonia and were hospitalized for management. We included patients confirmed positive for ≥ 1 virus by multiplex polymerase chain reaction assays (respiratory syncytial virus [RSV], human rhinovirus/enterovirus (hRV), human coronavirus (hCoV), metapneumovirus, parainfluenza virus, adenovirus, influenza viruses). We compared patient characteristics, clinical severity conventional outcomes (e.g., hospital length-of stay, 30-day mortality) and ordinal outcomes (5 levels: discharged, receiving convalescent care, acute ward or intensive care unit [ICU] care and death) for patients with NIRV infections and those with influenza.
RESULTS: Among 2119 adults who were admitted to hospital, 1156 patients (54.6%) had NIRV infections (hRV 14.9%, RSV 12.9%, hCoV 8.2%) and 963 patients (45.4%) had influenza (n = 963). Patients with NIRVs were younger (mean 66.4 [standard deviation 20.4] yr), and more commonly had immunocompromising conditions (30.3%) and delay in diagnosis (median 4.0 [interquartile range (IQR) 2.0–7.0] days). Overall, 14.6% (12.4%–19.5%) of NIRV infections were acquired in hospital. Admission to ICU (18.2%, median 6.0 [IQR 3.0–13.0] d), hospital length-of-stay (median 5.0 [IQR 2.0–10.0] d) and 30-day mortality (8.4%; RSV 9.5%, hRV 6.6%, hCoV 9.2%) and the ordinal outcomes were similar for patients with NIRV infection and those with influenza. Age > 60 years, immunocompromised state and hospital-acquired viral infection were associated with worse outcomes. The estimated median cost per acute care admission was $6000 (IQR $2000–$16 000).
INTERPRETATION: The burden of NIRV infection is substantial in adults admitted to hospital and associated outcomes may be as severe as for influenza, suggesting a need to prioritize therapeutics and vaccines for at-risk people.
The global burden of lower respiratory tract infections is substantial, leading to many hospital admissions and deaths, especially among young children and older adults.1 Respiratory viruses are responsible for almost half of such infections in adults that require in-hospital management; previous studies estimate that 28%–62% are caused by noninfluenza respiratory viruses (NIRVs).2–4 With some geographical and seasonal variations, respiratory syncytial virus (RSV), human rhinovirus (hRV) and human coronavirus (hCoV) are among the most frequently identified NIRV infections.1–7
Most infected adults develop mild, self-limiting illnesses, but increasing evidence suggest that NIRVs, either alone or with coinfecting bacteria, can result in severe pneumonia and death.8,9 For instance, RSV has been shown to cause severe respiratory failure, with fatality rates comparable to or exceeding those observed among adults admitted to hospital with influenza.10–12
Data on hRV, hCoV and other NIRVs are more limited, owing to the lack of accurate diagnostics and systematic case-finding approaches.7–9 However, with the increasing availability of multiplex polymerase chain reaction (PCR) assays that can simultaneously detect influenza and NIRVs, these infections are now readily diagnosed as part of a syndromic approach in patients who present with acute respiratory illnesses.2–5,13,14 The burden, clinical significance and impacts of NIRVs on the health care system remain inadequately characterized.
To address this gap, we analyzed the relative frequencies, patient characteristics, location of acquisition (community or hospital), severity and clinical outcomes of patients with NIRV and influenza infections diagnosed by multiplex PCR in a cohort of adults admitted to hospital in 2 large Canadian health care centres during a 3-year surveillance period. The associated health care resource use was also estimated.
(Continue . . . )
One of the big unknowns is what happens after COVID-19 runs its course.
Does influenza A quickly regain its prior position as king of the respiratory virus hill, or does something else - at least temporarily - fill the vacuum? If it is influenza A, will it be a return of H1N1 or H3N2, or will some other subtype seize the day?
We've essentially gone a year without influenza A or B, or any other (non-COVID) NRIV - and community immunity presumably wanes across the board with every passing month. Whether this situation changes this summer, next fall, or potentially sometime in 2022 or 2023, we will find ourselves in uncharted territory.
In the fall of 2017, in PLoS Comp. Bio.: Spring & Early Summer Most Likely Time For A Pandemic, we looked at a study that found that pandemics are most apt to emerge in the `off season', when novel viruses have less competition from other seasonal viruses, and community immunity is low.
While the big concern would be the emergence of a novel avian or swine flu virus, epidemics of `lesser' respiratory viruses - whether it be seasonal flu viruses, adenoviruses, enteroviruses, parainfluenza viruses, etc. - could prove daunting as well.
Today's study suggests that such an event - even with a noninfluenza respiratory virus - could produce substantial morbidity and mortality.
