The burden and severity of illness due to 2009 pandemic influenza A (H1N1) in a large US city during the late summer and early fall of 2009

Epidemiological features and trends in the mortality rates of 10 notifiable respiratory infectious diseases in China from 2004 to 2020: Based on national surveillance

Objectives

The aim of this study is to describe, visualize, and compare the trends and epidemiological features of the mortality rates of 10 notifiable respiratory infectious diseases in China from 2004 to 2020.

Setting

Data were obtained from the database of the National Infectious Disease Surveillance System (NIDSS) and reports released by the National and local Health Commissions from 2004 to 2020. Spearman correlations and Joinpoint regression models were used to quantify the temporal trends of RIDs by calculating annual percentage changes (APCs) in the rates of mortality.

Results

The overall mortality rate of RIDs was stable across China from 2004 to 2020 (R = -0.38, P = 0.13), with an APC per year of -2.2% (95% CI: -4.6 to 0.3; P = 0.1000). However, the overall mortality rate of 10 RIDs in 2020 decreased by 31.80% (P = 0.006) compared to the previous 5 years before the COVID-19 pandemic. The highest mortality occurred in northwestern, western, and northern China. Tuberculosis was the leading cause of RID mortality, and mortality from tuberculosis was relatively stable throughout the 17 years (R = -0.36, P = 0.16), with an APC of -1.9% (95% CI -4.1 to 0.4, P = 0.1000). Seasonal influenza was the only disease for which mortality significantly increased (R = 0.73, P = 0.00089), with an APC of 29.70% (95% CI 16.60-44.40%; P = 0.0000). The highest yearly case fatality ratios (CFR) belong to avian influenza A H5N1 [687.5 per 1,000 (33/48)] and epidemic cerebrospinal meningitis [90.5748 per 1,000 (1,010/11,151)]. The age-specific CFR of 10 RIDs was highest among people over 85 years old [13.6551 per 1,000 (2,353/172,316)] and was lowest among children younger than 10 years, particularly in 5-year-old children [0.0552 per 1,000 (58/1,051,178)].

Conclusions

The mortality rates of 10 RIDs were relatively stable from 2004 to 2020 with significant differences among Chinese provinces and age groups. There was an increased mortality trend for seasonal influenza and concerted efforts are needed to reduce the mortality rate of seasonal influenza in the future.

Emergency Department Utilization and Patient Outcomes During the COVID-19 Pandemic in America

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic precipitated fear of contagion and influenced many people to avoid the emergency department (ED). It is unknown if this avoidance effected overall health or disease mortality.

OBJECTIVE

We aimed to quantify the decreased ED volume in the United States, determine whether it occurred simultaneously across the country, find which types of patients decreased, and measure resultant changes in patient outcomes.

METHODS

We retrospectively accessed a multihospital, multistate electronic health records database managed by HCA Healthcare to obtain a case series of all patients presenting to an ED during the early COVID-19 pandemic (March 1-May 31, 2020) and the same dates in 2019 for comparison. We determined ED volume using weekly totals and grouped them by state. We also recorded final diagnoses codes and mortality data to describe patient types and outcomes.

RESULTS

The weekly ED volume from 160 facilities dropped 44% from 141,408 patients (week 1, March 1-7, 2020) to a nadir of 79,618 patients (week 7, April 12-18, 2020), before rising back to 105,667 (week 13, May 24-30, 2020). Compared with 2019, this overall decline was statistically significant (p < 0.001). The decline was universal across disease categories except for infectious disease and respiratory illnesses, which increased. All-cause mortality increased during the pandemic, especially for those with infectious disease, circulatory, and respiratory illnesses.

CONCLUSIONS

The COVID-19 pandemic and an apparent fear of contagion caused a decrease in ED presentations across our hospital system. The decline in ED volume was associated with increased ED mortality, perhaps from delayed ED presentations.

Emergency Medical Services Personnel's Pandemic Influenza Training Received and Willingness to Work during a Future Pandemic

Objective: Identify determinants of emergency medical service (EMS) personnel's willingness to work during an influenza pandemic. Background: Little is known about the willingness of EMS personnel to work during a future influenza pandemic or the extent to which they are receiving pandemic training. Methods: EMS personnel were surveyed in July 2018 - Feb 2019 using a cross-sectional approach; the survey was available both electronically and on paper. Participants were provided a pandemic scenario and asked about their willingness to respond if requested or required; additional questions assessed their attitudes and beliefs and training received. Chi-square tests assessed differences in attitude/belief questions by willingness to work. Logistic regressions were used to identify significant predictors of response willingness when requested or required, controlling for gender and race. Results: 433 individuals completed the survey (response rate = 82.9%). A quarter (26.8%, n = 116) received no pandemic training; 14.3% (n = 62) participated in a pandemic exercise. Significantly more EMS personnel were willing to work when required versus when only requested (88.2% vs 76.9%, X2 = 164.1, p < .001). Predictors of willingness to work when requested included believing it is their responsibility to work, believing their coworkers were likely to work, receiving prophylaxis for themselves and their family members, and feeling safe working during a pandemic. Discussion: Many emergency medical services personnel report lacking training or disaster exercises related to influenza pandemics, and a fair percentage are unwilling to work during a future event. This may limit healthcare surge capacity and could contribute to increased morbidity and mortality. Findings from this study indicate that prehospital staff's attitudes and beliefs about pandemics influence their willingness to work. Pre-event training and planning should address these concerns.

Utility of state-level influenza disease burden and severity estimates to investigate an apparent increase in reported severe cases of influenza A(H1N1) pdm09 - Arizona, 2015-2016

The Arizona Department of Health Services identified unusually high levels of influenza activity and severe complications during the 2015-2016 influenza season leading to concerns about potential increased disease severity compared with prior seasons. We estimated state-level burden and severity to compare across three seasons using multiple data sources for community-level illness, hospitalisation and death. Severity ratios were calculated as the number of hospitalisations or deaths per community case. Community influenza-like illness rates, hospitalisation rates and mortality rates in 2015-2016 were higher than the previous two seasons. However, ratios of severe disease to community illness were similar. Arizona experienced overall increased disease burden in 2015-2016, but not increased severity compared with prior seasons. Timely estimates of state-specific burden and severity are potentially feasible and may provide important information during seemingly unusual influenza seasons or pandemic situations.

Annual Burden of Occupationally-Acquired Influenza Infections in Hospitals and Emergency Departments in the United States

Infections among health-care personnel (HCP) occur as a result of providing care to patients with infectious diseases, but surveillance is limited to a few diseases. The objective of this study is to determine the annual number of influenza infections acquired by HCP as a result of occupational exposures to influenza patients in hospitals and emergency departments (EDs) in the United States. A risk analysis approach was taken. A compartmental model was used to estimate the influenza dose received in a single exposure, and a dose-response function applied to calculate the probability of infection. A three-step algorithm tabulated the total number of influenza infections based on: the total number of occupational exposures (tabulated in previous work), the total number of HCP with occupational exposures, and the probability of infection in an occupational exposure. Estimated influenza infections were highly dependent upon the dose-response function. Given current compliance with infection control precautions, we estimated 151,300 and 34,150 influenza infections annually with two dose-response functions (annual incidence proportions of 9.3% and 2.1%, respectively). Greater reductions in infectious were achieved by full compliance with vaccination and IC precautions than with patient isolation. The burden of occupationally-acquired influenza among HCP in hospitals and EDs in the United States is not trivial, and can be reduced through improved compliance with vaccination and preventive measures, including engineering and administrative controls.

Influenza and other respiratory viruses: standardizing disease severity in surveillance and clinical trials

INTRODUCTION

Influenza-Like Illness is a leading cause of hospitalization in children. Disease burden due to influenza and other respiratory viral infections is reported on a population level, but clinical scores measuring individual changes in disease severity are urgently needed. Areas covered: We present a composite clinical score allowing individual patient data analyses of disease severity based on systematic literature review and WHO-criteria for uncomplicated and complicated disease. The 22-item ViVI Disease Severity Score showed a normal distribution in a pediatric cohort of 6073 children aged 0-18 years (mean age 3.13; S.D. 3.89; range: 0 to 18.79). Expert commentary: The ViVI Score was correlated with risk of antibiotic use as well as need for hospitalization and intensive care. The ViVI Score was used to track children with influenza, respiratory syncytial virus, human metapneumovirus, human rhinovirus, and adenovirus infections and is fully compliant with regulatory data standards. The ViVI Disease Severity Score mobile application allows physicians to measure disease severity at the point-of care thereby taking clinical trials to the next level.

Relative incidence and individual-level severity of seasonal influenza A H3N2 compared with 2009 pandemic H1N1

Background

Two subtypes of influenza A currently circulate in humans: seasonal H3N2 (sH3N2, emerged in 1968) and pandemic H1N1 (pH1N1, emerged in 2009). While the epidemiological characteristics of the initial wave of pH1N1 have been studied in detail, less is known about its infection dynamics during subsequent waves or its severity relative to sH3N2. Even prior to 2009, few data was available to estimate the risk of severe outcomes following infection with one circulating influenza strain relative to another.

Methods

We analyzed antibodies in quadruples of sera from individuals in Hong Kong collected between July 2009 and December 2011, a period that included three distinct influenza virus epidemics. We estimated infection incidence using these assay data and then estimated rates of severe outcomes per infection using population-wide clinical data.

Results

Cumulative incidence of infection was high among children in the first epidemic of pH1N1. There was a change towards the older age group in the age distribution of infections for pH1N1 from the first to the second epidemic, with the age distribution of the second epidemic of pH1N1 more similar to that of sH3N2. We found no serological evidence that individuals were infected in both waves of pH1N1. The risks of excess mortality conditional on infection were higher for sH3N2 than for pH1N1, with age-standardized risk ratios of 2.6 [95% CI: 1.8, 3.7] for all causes and 1.5 [95% CI: 1.0, 2.1] for respiratory causes throughout the study period.

Conclusions

Overall increase in clinical incidence of pH1N1 and higher rates of severity in older adults in post pandemic waves were in line with an age-shift in infection towards the older age groups. The absence of repeated infection is good evidence that waning immunity did not cause the second wave. Despite circulating in humans since 1968, sH3N2 is substantially more severe per infection than the pH1N1 strain. Infection-based estimates of individual-level severity have a role in assessing emerging strains; updating seasonal vaccine components; and optimizing of vaccination programs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2432-7) contains supplementary material, which is available to authorized users.

Estimating the Burden of Pandemic Infectious Disease: The Case of the Second Wave of Pandemic Influenza H1N1 in Forsyth County, North Carolina

BACKGROUND

Understanding the burden of influenza A(H1N1)pdm09 virus during the second wave of 2009-2010 is important for future pandemic planning.

METHODS

Persons who presented to the emergency department (ED) or were hospitalized with fever and/or acute respiratory symptoms at the academic medical center in Forsyth County, North Carolina were prospectively enrolled and underwent nasal/throat swab testing for influenza A(H1N1)pdm09. Laboratory-confirmed cases of influenza A(H1N1)pdm09 virus identified through active surveillance were compared by capture-recapture analysis to those identified through independent, passive surveillance (physician-ordered influenza testing). This approach estimated the number of total cases, including those not captured by either surveillance method. A second analysis estimated the total number of influenza A(H1N1)pdm09 cases by multiplying weekly influenza percentages determined via active surveillance by weekly counts of influenza-associated discharge diagnoses from administrative data. Market share adjustments were used to estimate influenza A(H1N1)pdm09 virus ED visits or hospitalizations per 1,000 residents.

RESULTS

Capture-recapture analysis estimated that 753 residents (95% confidence interval [CI], 424-2,735) with influenza A(H1N1)pdm09 virus were seen in the academic medical center from September 2009 through mid-April 2010; this result yielded an estimated 4.7 (95% CI, 2.6-16.9) influenza A(H1N1)pdm09 virus ED visits or hospitalizations per 1,000 residents. Similarly, 708 visits were estimated using weekly influenza percentages and influenza-associated discharge diagnoses, yielding an estimated 4.4 influenza A(H1N1)pdm09 virus ED visits or hospitalizations per 1,000 residents.

CONCLUSION

This study demonstrates that the burden of influenza A(H1N1)pdm09 virus in ED and inpatient settings by capture-recapture analysis was 4-5 per 1,000 residents; this rate was approximately 8-fold higher than that detected by physician-ordered influenza testing.

Occupational exposures to influenza among healthcare workers in the United States

The objective of this study is to estimate the annual number of occupational exposures to influenza among healthcare workers that result from providing direct and supportive care to influenza patients in acute care, home care and long-term care settings. Literature review was used to identify healthcare utilization for influenza, and worker activity patterns. This information was used, with Monte Carlo simulation, to tabulate the mean annual number of occupational exposures. Given a medium-sized epidemic with a 6% annual symptomatic influenza incidence proportion, the mean number of occupational exposures was estimated to be 81.8 million annually. Among the approximately 14 million healthcare workers, this corresponds to 5.8 exposures per worker annually, on average. Exposures, however, are likely concentrated among subsets of healthcare workers. Occupational exposures were most numerous in ambulatory care settings (38%), followed by long-term care facilities (30%) and home care settings (21%). The annual number of occupational exposures to influenza is high, but not every occupational exposure will result in infection. Some infection control activities, like patient isolation, can reduce the number of occupational exposures.

Pediatric triage and allocation of critical care resources during disaster: Northwest provider opinion

INTRODUCTION

Following Hurricane Katrina and the 2009 H1N1 epidemic, pediatric critical care clinicians recognized the urgent need for a standardized pediatric triage/allocation system. This study collected regional provider opinion on issues of care allocation and pediatric triage in a disaster/pandemic setting.

METHODS

This study was a cross-sectional survey of United States (US) health care providers and public health workers who demonstrated interest in critical care and/or disaster care medicine by attending a Northwest regional pediatric critical care symposium on disaster preparation, held in 2012 at Seattle Children's Hospital in Seattle, Washington (USA). The survey employed an electronic audience response system and included demographic, ethical, and logistical questions. Differences in opinions between respondents grouped by professions and work locations were evaluated using a chi-square test.

RESULTS

One hundred and twelve (97%) of 116 total attendees responded to at least one question; however, four of these responders failed to answer every question. Sixty-two (55%) responders were nurses, 29 (26%) physicians, and 21 (19%) other occupations. Fifty-five (51%) responders worked in pediatric hospitals vs 53 (49%) in other locations. Sixty-three (58%) of 108 successful responses prioritized children predicted to have a good neuro-cognitive outcome. Seventy-one (68%) agreed that no pediatric age group should be prioritized. Twenty-two (43%) of providers working in non-pediatric hospital locations preferred a triage system based on an objective score alone vs 14 (26%) of those in pediatric hospitals (P = .038).

Case fatality risk of influenza A (H1N1pdm09): a systematic review

BACKGROUND

During the 2009 influenza pandemic, uncertainty surrounding the seriousness of human infections with the H1N1pdm09 virus hindered appropriate public health response. One measure of seriousness is the case fatality risk, defined as the probability of mortality among people classified as cases.

METHODS

We conducted a systematic review to summarize published estimates of the case fatality risk of the pandemic influenza H1N1pdm09 virus. Only studies that reported population-based estimates were included.

RESULTS

We included 77 estimates of the case fatality risk from 50 published studies, about one-third of which were published within the first 9 months of the pandemic. We identified very substantial heterogeneity in published estimates, ranging from less than 1 to more than 10,000 deaths per 100,000 cases or infections. The choice of case definition in the denominator accounted for substantial heterogeneity, with the higher estimates based on laboratory-confirmed cases (point estimates = 0-13,500 per 100,000 cases) compared with symptomatic cases (point estimates = 0-1,200 per 100,000 cases) or infections (point estimates = 1-10 per 100,000 infections). Risk based on symptomatic cases increased substantially with age.

CONCLUSIONS

Our review highlights the difficulty in estimating the seriousness of infection with a novel influenza virus using the case fatality risk. In addition, substantial variability in age-specific estimates complicates the interpretation of the overall case fatality risk and comparisons among populations. A consensus is needed on how to define and measure the seriousness of infection before the next pandemic.