scholarly journals Evolution of human respiratory virus epidemics

F1000Research ◽  
2021 ◽  
Vol 10 ◽  
pp. 447
Author(s):  
Nash Rochman ◽  
Yuri Wolf ◽  
Eugene V. Koonin
Keyword(s):  
Disease Burden ◽  
Herd Immunity ◽  
Public Health Intervention ◽  
Case Fatality ◽  
Compartment Model ◽  
Major Effect ◽  
Mathematical Framework ◽  
Human Pathogens ◽  
Evolutionary Trajectory ◽  
Pathogen Fitness

Background: It is often assumed that pathogens evolve towards reduced virulence, but counterexamples abound. Faced with a new pathogen, such as SARS-CoV-2, it is highly desirable to be able to forecast the case fatality rate (CFR) and overall disease burden into the future. Considerable effort has been invested towards the development of a mathematical framework for predicting virulence evolution. Although many approaches accurately recapitulate complex outcomes, most rely on an assumed trade-off between CFR and infection rate. It is often impractical to empirically validate this constraint for human pathogens. Methods: A compartment model with parameters tuning the degree to which symptomatic individuals are isolated and the duration of immunity is constructed and evaluated at both short timescales and at equilibrium (when it exists). Results: We reveal kinetic constraints where the variation of multiple parameters in concert leads to decreased CFR and increased pathogen fitness, whereas independent variation of the parameters decreases pathogen fitness. Smallpox, SARS-CoV-2, and influenza are analyzed as diverse representatives of human respiratory viruses. We show that highly virulent viruses, such as smallpox, are likely often constrained by host behavior, whereas moderately virulent viruses, such as SARS-CoV-2, appear to be typically constrained by the relationship between the duration of immunity and CFR. Conclusions: Evolution of human respiratory epidemics appears to be often kinetically constrained and a reduction in CFR should not be assumed. Our findings imply that, without continued public health intervention, SARS-CoV-2 is likely to continue presenting a substantial disease burden. The existence of a parameter regime admitting endemic equilibrium suggests that herd immunity is unachievable. However, we demonstrate that even partial isolation of symptomatic individuals can have a major effect not only by reducing the number of fatalities in the short term but also by potentially changing the evolutionary trajectory of the virus towards reduced CFR.

scholarly journals Evolution of Human Respiratory Virus Epidemics

2020 ◽  
Author(s):  
Nash D. Rochman ◽  
Yuri I. Wolf ◽  
Eugene V. Koonin
Keyword(s):  
Herd Immunity ◽  
Public Health Intervention ◽  
Case Fatality ◽  
Compartment Model ◽  
Major Effect ◽  
Mathematical Framework ◽  
Human Pathogens ◽  
Evolutionary Trajectory ◽  
Multiple Parameters ◽  
Pathogen Fitness

AbstractBackgroundWhile pathogens often evolve towards reduced virulence, many counterexamples are evident. When faced with a new pathogen, such as SARS-CoV-2, it is highly desirable to be able to forecast the case fatality rate (CFR) into the future. Considerable effort has been invested towards the development of a mathematical framework for predicting virulence evolution. Although these approaches accurately recapitulate some complex outcomes, most rely on an assumed trade-off between mortality and infectivity. It is often impractical to empirically validate this constraint for human pathogens.ResultsUsing a compartment model with parameters tuning the degree to which symptomatic individuals are isolated and the duration of immunity, we reveal kinetic constraints where the variation of multiple parameters in concert leads to decreased virulence and increased pathogen fitness, whereas independent variation of the parameters decreases pathogen fitness. Smallpox, SARS-CoV-2, and Influenza are analyzed as diverse representatives of human respiratory viruses. We show that highly virulent viruses, such as Smallpox, are likely often constrained by host behavior, whereas moderately virulent viruses, such as SARS-CoV-2, appear to be typically constrained by the relationship between the duration of immunity and CFR.ConclusionsThe evolution of human respiratory epidemics appears to be often kinetically constrained and a reduction in virulence should not be assumed. Our findings imply that, without continued public health intervention, SARS-CoV-2 is likely to continue presenting a substantial disease burden. The existence of a parameter regime admitting endemic equilibrium suggests that herd immunity is unachievable. However, we demonstrate that even partial isolation of symptomatic individuals can have a major effect not only by reducing the number of fatalities in the short term but also by potentially changing the evolutionary trajectory of the virus towards reduced virulence.

scholarly journals Evolution of human respiratory virus epidemics

F1000Research ◽  
2021 ◽  
Vol 10 ◽  
pp. 447
Author(s):  
Nash Rochman ◽  
Yuri Wolf ◽  
Eugene V. Koonin
Keyword(s):  
Disease Burden ◽  
Herd Immunity ◽  
Case Fatality ◽  
Compartment Model ◽  
Major Effect ◽  
Mathematical Framework ◽  
Human Pathogens ◽  
Evolutionary Trajectory ◽  
Epidemic Dynamics ◽  
Pathogen Fitness

Background: Pathogens are often assumed to evolve towards reduced virulence, but counterexamples abound. Faced with a new pathogen, such as SARS-CoV-2, it is crucial to be able to forecast the case fatality rate (CFR) and the overall disease burden. Considerable effort has been invested towards developing a mathematical framework for predicting virulence evolution. Although many approaches accurately recapitulate complex outcomes, most rely on an assumed trade-off between CFR and infection rate. It is often impractical to empirically validate this constraint for human pathogens. Methods: A compartment model with parameters tuning the degree to which symptomatic individuals are isolated and the duration of immunity is constructed and evaluated at both short timescales and at equilibrium. Results: We reveal kinetic constraints whereby variation of multiple parameters in concert leads to decreased CFR and increased pathogen fitness, whereas independent variation of the parameters decreases pathogen fitness. Smallpox, SARS-CoV-2, and influenza are analyzed as diverse representatives of human respiratory viruses. We show that highly virulent viruses, such as smallpox, are often constrained by the host behavior, whereas moderately virulent viruses, such as SARS-CoV-2, appear to be typically constrained by the relationship between the duration of immunity and CFR. Conclusions: Evolution of human respiratory epidemics appears to be often kinetically constrained and a reduction in CFR should not be assumed. These results agree with previous work demonstrating an increase in virulence for smallpox and further predict that SARS-CoV-2 is likely to continue presenting a substantial disease burden. Herd immunity against SARS-CoV-2 and viruses with similar life history traits might be unachievable without vaccination. However, partial isolation of symptomatic individuals can have a major effect on the epidemic dynamics not only by reducing the number of fatalities in the short term but also by changing the evolutionary trajectory of moderate CFR viruses towards reduced CFR.

scholarly journals A general model for the demographic signatures of the transition from pandemic emergence to endemicity

2021 ◽  
Vol 7 (33) ◽  
pp. eabf9040
Author(s):  
Ruiyun Li ◽  
C. Jessica E. Metcalf ◽  
Nils Chr. Stenseth ◽  
Ottar N. Bjørnstad
Keyword(s):  
Human Population ◽  
Disease Burden ◽  
Mitigation Strategies ◽  
Mathematical Framework ◽  
Human Pathogens ◽  
Incidence And Mortality ◽  
Social Mixing ◽  
Mixing Patterns ◽  
Age Structured

Anticipating the medium- and long-term trajectory of pathogen emergence has acquired new urgency given the ongoing COVID-19 pandemic. For many human pathogens, the burden of disease depends on age and previous exposure. Understanding the intersection between human population demography and transmission dynamics is therefore critical. Here, we develop a realistic age-structured mathematical model that integrates demography, social mixing, and immunity to establish a plausible range for future age incidence and mortality. With respect to COVID-19, we identify a plausible transition in the age structure of risks once the disease reaches seasonal endemism across a range of immunity durations and relative severity of primary versus subsequent reinfections. We train the model using diverse real-world demographies and age-structured mixing to bound expectations for changing age incidence and disease burden. The mathematical framework is flexible and can help tailor mitigation strategies in countries worldwide with varying demographies and social mixing patterns.

scholarly journals A general model for the demographic signatures of the transition from pandemic emergence to endemicity

2021 ◽  
Author(s):  
Ruiyun Li ◽  
C. Jessica E. Metcalf ◽  
Nils Chr. Stenseth ◽  
Ottar N Bjornstad
Keyword(s):  
Protective Immunity ◽  
Human Population ◽  
Disease Burden ◽  
Mitigation Strategies ◽  
Mathematical Framework ◽  
Human Pathogens ◽  
Social Mixing ◽  
Mixing Patterns ◽  
Age Structured

Anticipating the medium- and long-term trajectory of pathogen emergence has acquired new urgency given the ongoing COVID-19 pandemic. For many human pathogens the burden of disease depends on age and prior exposure. Understanding the intersection between human population demography and transmission dynamics is therefore critical. Here, we develop a realistic age-structured (RAS) mathematical model that integrates demography, social mixing and immunity to establish the suite of possible scenarios of future age-incidence and burden of mortality. With respect to COVID-19, we identify a plausible transition in the age-structure of risks once the disease reaches seasonal endemism, whether assuming long-lasting or brief protective immunity, and across a range of assumptions of relative severity of primary versus subsequent reinfections. We train the model using diverse real-world demographies and age-structured social mixing patterns to bound expectations for changing age-incidence and disease burden. The mathematical framework is flexible and can help tailoring mitigation strategies countries worldwide with varying demographies and social mixing patterns.

scholarly journals Association of COVID-19 case fatality rate with disease burden: an ecological analysis in Italy during the first wave

2021 ◽  
Vol 111 ◽  
pp. 186-189
Author(s):  
Laura Timelli ◽  
Giuseppina Liuzzi ◽  
Alessandro Cannavacciuolo ◽  
Nicola Petrosillo ◽  
Vincenzo Puro ◽  
...  
Keyword(s):  
Case Fatality Rate ◽  
Disease Burden ◽  
Case Fatality ◽  
Fatality Rate ◽  
Ecological Analysis

Seroprevalence ofBordetella pertussisin the Mexican population: a cross-sectional study

2013 ◽  
Vol 142 (4) ◽  
pp. 706-713 ◽  
Author(s):  
C. CONDE-GLEZ ◽  
E. LAZCANO-PONCE ◽  
R. ROJAS ◽  
R. DeANTONIO ◽  
L. ROMANO-MAZZOTTI ◽  
...  
Keyword(s):  
Socioeconomic Status ◽  
Disease Burden ◽  
Public Health Intervention ◽  
Booster Vaccination ◽  
Cross Sectional Study ◽  
Serum Samples ◽  
Nutrition Survey ◽  
Cross Sectional ◽  
Health And Nutrition ◽  
Sources Of Infection

SUMMARYSerum samples collected during the National Health and Nutrition survey (ENSANUT 2006) were obtained from subjects aged 1–95 years (January–October 2010) and analysed to assess the seroprevalence ofBordetella pertussis(BP) in Mexico. Subjects' gender, age, geographical region and socioeconomic status were extracted from the survey and compiled into a subset database. A total of 3344 subjects (median age 29 years, range 1–95 years) were included in the analysis. Overall, BP seroprevalence was 47·4%. BP seroprevalence was significantly higher in males (53·4%,P = 0·0007) and highest in children (59·3%) decreasing with advancing age (P = 0·0008). BP seroprevalence was not significantly different between regions (P = 0·1918) and between subjects of socioeconomic status (P = 0·0808). Women, adolescents and young adults were identified as potential sources of infection to infants. Booster vaccination for adolescents and primary contacts (including mothers) for newborns and infants may provide an important public health intervention to reduce the disease burden.

Understanding vaccine hesitancy: the evidence

2021 ◽  
Vol 32 (7) ◽  
pp. 282-287
Author(s):  
Alison While
Keyword(s):  
Public Health ◽  
Health Professionals ◽  
Herd Immunity ◽  
Public Health Intervention ◽  
Health Intervention ◽  
Vaccine Hesitancy ◽  
Important Public Health ◽  
Positive Attitudes ◽  
The Uk

Vaccine hesitancy is a concern both globally and within the UK. Alison While reviews the evidence relating to vaccine hesitancy, its underlying factors and the sociodemographic variations Vaccination is an important public health intervention, but its effectiveness depends upon the uptake of vaccination reaching sufficient levels to yield ‘herd’ immunity. While the majority of the UK hold positive attitudes about vaccination, some people, including health professionals, decline vaccinations. This article reviews the evidence relating to vaccine hesitancy, its underlying factors and the sociodemographic variations.

scholarly journals COVID-19 Healthcare Planning: Predicting Mortality and the Role of the Herd Immunity Barrier in the General Population

2020 ◽  
Vol 12 (13) ◽  
pp. 5228
Author(s):  
Julio Emilio Marco-Franco ◽  
Natividad Guadalajara-Olmeda ◽  
Silvia González-de Julián ◽  
David Vivas-Consuelo
Keyword(s):  
General Population ◽  
Case Fatality Rate ◽  
Meta Analysis ◽  
Herd Immunity ◽  
Case Fatality ◽  
Fatality Rate ◽  
Daily Monitoring ◽  
Age Related ◽  
The Impact ◽  
Carlos Iii

Using a mathematical model for COVID-19 incorporating data on excess of mortality compared to the corresponding period of the previous year obtained from the daily monitoring of mortality in Spain (MoMo), the prediction of total number of casualties in Spain for the first outbreak has been computed. From this figure, and following a stepwise meta-analysis of available reports, the case fatality rate (CFR) and the infectious case fatality rate (IFR) for the outbreak have been estimated. As the impact of age on these rates is notable, it is proposed to include an age-related adjusted fatality ratio in future comparative analyses between studies, calculated by adjusting the results by risk ratio to a reference age band (e.g., 60–69). From the casualty figures, and the corresponding CFR and IFR ratios, the forecast of serologically positive cases in the general Spanish population has been estimated at approximately 1% (0.87–1.3%) of the samples. If the data are confirmed by the ongoing study of the Carlos III Institute, until a vaccine is found, the immunity acquired in the general population after the infectious outbreak is far from the 65–70% herd immunity required as a barrier for COVID-19.

scholarly journals The Epidemiology of Herpes Zoster in Immunocompetent, Unvaccinated Adults ≥50 Years Old: Incidence, Complications, Hospitalization, Mortality, and Recurrence

2019 ◽  
Vol 222 (5) ◽  
pp. 798-806 ◽  
Author(s):  
Hung Fu Tseng ◽  
Katia Bruxvoort ◽  
Bradley Ackerson ◽  
Yi Luo ◽  
Hilary Tanenbaum ◽  
...  
Keyword(s):  
Herpes Zoster ◽  
Disease Burden ◽  
Health Care Organization ◽  
Case Fatality ◽  
Recurrence Risk ◽  
Care Organization ◽  
Health Records ◽  
Epidemiology Data ◽  
Potential Impact ◽  
Immunocompetent Adults

Abstract Background Data on the epidemiology of herpes zoster (HZ), particularly in the unvaccinated immunocompetent population, are needed to assess disease burden and the potential impact of vaccination. Methods The study at a large health care organization comprised: (1) incidence estimated from immunocompetent adults aged ≥50 years unvaccinated with zoster vaccine live who had incident HZ in 2011–2015; (2) proportion of HZ-related nonpain complications assessed by double abstraction of electronic health records (EHRs) of 600 incident patients 2011–2015; (3) HZ-related hospitalizations among HZ patients diagnosed in 2015; (4) HZ-related death determined from automated data and EHRs; and (5) recurrent HZ identified from a cohort initially diagnosed with HZ in 2007–2008 and followed through 2016. Results HZ incidence rate was 9.92/1000 person-years (95% confidence interval [CI], 9.82–10.01). Proportions of cutaneous, neurologic, and other complications were 6.40% (95% CI,1.73%–11.07%), 0.77% (95% CI, .00%–2.36%), and 1.01% (95% CI, .00%–2.93%), respectively. Only 0.86% of patients had an HZ-related hospitalization. The case-fatality rate was 0.04%. Recurrence rate was 10.96/1000 person-years (95% CI, 10.18–11.79) with 10-year recurrence risk of 10.26% (95% CI, 9.36%–11.23%). Conclusions These recent HZ epidemiology data among an immunocompetent, unvaccinated population measure real-world disease burden.

scholarly journals 2716. Persistence of 13-Valent Pneumococcal Conjugate Vaccine (PCV13) Serotypes in Invasive Pneumococcal Disease in Adults in Southern Ontario Canada Despite Routine Pediatric Vaccination

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S955-S956
Author(s):  
Allison McGeer ◽  
Agron Plevneshi ◽  
Karen Green ◽  
Brenda Coleman ◽  
Sarah Nayani ◽  
...  
Keyword(s):  
Invasive Pneumococcal Disease ◽  
Pneumococcal Disease ◽  
Medical Information ◽  
Herd Immunity ◽  
Case Fatality ◽  
Population Data ◽  
Vaccination Programs ◽  
Significant Difference ◽  
Statistics Canada ◽  
Pediatric Vaccination

Abstract Background In Ontario, Canada, PCV13 is covered for immunocompromised (IC) adults over 50y. PCV13 programs are thought not to be cost-effective in other adults because it is assumed that herd immunity from pediatric vaccination programs (PCV7 since 2005; PCV13 since 2010) will reduce PCV13 disease burden dramatically in adults. We analyzed data from the Toronto Invasive Bacterial Diseases Network (TIBDN) to ask whether PCV13-type invasive pneumococcal disease (IPD) in adults persists in our population. Methods TIBDN performs population-based surveillance for IPD in Toronto+Peel Region, Ontario (pop4.1M). All microbiology laboratories receiving specimens from residents report cases of IPD and submit isolates to a central study lab for serotyping; annual audits are conducted. Demographic, medical and vaccination information are obtained from patients, families and physicians. Population data are from Statistics Canada. Results Since 1995, 10,365 episodes of IPD have been identified; detailed medical information was available for 9,801 (95%) and serotyping for 9411 (91%). Among 8658 adult cases, 4,273 (49%) were in those aged 15–64 years, and 4,285 (51%) in those aged >645 years. The most common diagnoses were pneumonia (5,978/8,025, 74%) and bacteremia without focus (1,030, 13%); 470 (4.6%) cases had meningitis; the case fatality rate (CFR) was 21%. The incidence of disease due to STs in PCV13 in adults declined from 7.0/100,000/year 2001 to 2.9/100,000/year in 2015–2018 and was stable from 2015–2018 (Figure 1). The incidence was > 5/100,000/year in non-IC patients over 65 years, and younger patients with cancer and kidney disease (Figure 2). In IPD from 2015 to 2018, adult patients with PCV13 ST disease were younger (median age 64 years vs. 67 years, P = .03) than other patients; there was no significant difference in the proportion with at least one underlying chronic condition (253, 69% PCV13ST, vs. 541,74% other ST, P = 0.08), or in CFR (59, 16% PCV13 vs. 145, 20% other, P = 0.13). The ST distribution of cases due to PCV13 STs is shown in Figure 3. Conclusion A significant burden of IPD due to PCV13 serotypes persists in adults in our population despite 8 years of routine pediatric PCV13 vaccination. This burden needs to be considered in assessing the value and cost-effectiveness of PCV programs for adults. Disclosures All authors: No reported disclosures.

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