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 ◽  
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

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.

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 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.

scholarly journals Rapid, Simultaneous Detection ofClostridium sordelliiandClostridium perfringensin Archived Tissues by a Novel PCR-Based Microsphere Assay: Diagnostic Implications for Pregnancy-Associated Toxic Shock Syndrome Cases

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Julu Bhatnagar ◽  
Marlene DeLeon-Carnes ◽  
Kathryn L. Kellar ◽  
Kakali Bandyopadhyay ◽  
Zoi-Anna Antoniadou ◽  
...  
Keyword(s):  
Clostridium Perfringens ◽  
Simultaneous Detection ◽  
Case Fatality ◽  
Cost Effective ◽  
Human Pathogens ◽  
Toxic Shock ◽  
Clostridium Sordellii ◽  
Formalin Fixed Paraffin Embedded ◽  
Ffpe Tissues ◽  
Species Specific

Clostridium sordelliiandClostridium perfringensare infrequent human pathogens; however, the case-fatality rates for the infections are very high, particularly in obstetricC. sordelliiinfections (>90%). Deaths fromClostridium sordelliiandClostridium perfringenstoxic shock (CTS) are sudden, and diagnosis is often challenging. Formalin-fixed, paraffin-embedded (FFPE) tissues usually are the only specimens available for sudden fatal cases, and immunohistochemistry (IHC) for Clostridia is generally performed but it cannot identify species. A clear need exists for a rapid, species-specific diagnostic assay for FFPE tissues. We developed a duplex PCR-based microsphere assay for simultaneous detection ofC. sordelliiandC. perfringensand evaluated DNA extracted from 42Clostridiumisolates and FFPE tissues of 28 patients with toxic shock/endometritis (20 CTS, 8 non-CTS, as confirmed by PCR and sequencing). The microsphere assay correctly identifiedC. sordelliiandC. perfringensin all known isolates and in all CTS patients (10C. sordellii, 8C. perfringens, 2 both) and showed 100% concordance with PCR and sequencing results. The microsphere assay is a rapid, specific, and cost-effective method for the diagnosis of CTS and offers the advantage of simultaneous testing forC. sordelliiandC. perfringensin FFPE tissues using a limited amount of DNA.

scholarly journals Modeling the COVID-19 outbreaks and the effectiveness of the containment measures adopted across countries

2020 ◽  
Author(s):  
Edward De Brouwer ◽  
Daniele Raimondi ◽  
Yves Moreau
Keyword(s):  
Herd Immunity ◽  
Case Fatality ◽  
Severe Pneumonia ◽  
Optimal Level ◽  
World Health ◽  
Reproduction Ratio ◽  
The Public ◽  
Global Pandemic ◽  
Containment Measures ◽  
Health Organization

AbstractOn March 11, 2020, the World Health Organization declared the COVID-19 outbreak, originally started in China, a global pandemic. Since then, the outbreak has indeed spread across all continents, threatening the public health of numerous countries. Although the Case Fatality Rate (CFR) of COVID-19 is relatively low when optimal level of healthcare is granted to the patients, the high percentage of severe cases developing severe pneumonia and thus requiring respiratory support is worryingly high, and could lead to a rapid saturation of Intensive Care Units (ICUs). To overcome this risk, most countries enacted COVID-19 containment measures. In this study, we use a Bayesian SEIR epidemiological model to perform a parametric regression over the COVID-19 outbreaks data in China, Italy, Belgium, and Spain, and estimate the effect of the containment measures on the basic reproduction ratio R0.We find that the effect of these measures is detectable, but tends to be gradual, and that a progressive strengthening of these measures usually reduces the R0 below 1, granting a decay of the outbreak. We also discuss the biases and inconsistencies present in the publicly available data on COVID-19 cases, providing an estimate for the actual number of cases in Italy on March 12, 2020. Lastly, despite the data and model’s limitations, we argue that the idea of “flattening the curve” to reach herd immunity is likely to be unfeasible.

scholarly journals Epidemiology of the Zika virus outbreak in the Cabo Verde Islands, West Africa

2017 ◽  
Author(s):  
José Lourenço ◽  
Maria de Lourdes Monteiro ◽  
Tomás Valdez ◽  
Júlio Monteiro Rodrigues ◽  
Oliver G. Pybus ◽  
...  
Keyword(s):  
West Africa ◽  
Zika Virus ◽  
Attack Rate ◽  
Herd Immunity ◽  
Basic Reproductive Number ◽  
Reproductive Number ◽  
Mathematical Framework ◽  
Single Wave ◽  
Cabo Verde ◽  
Small Observation

AbstractIntroductionThe Zika virus (ZIKV) outbreak in the island nation of Cabo Verde was of unprecedented magnitude in Africa and the first to be associated with microcephaly in the continent.MethodsUsing a simple mathematical framework we present a first epidemiological assessment of attack and observation rates from 7,580 ZIKV notified cases and 18 microcephaly reports between July 2015 and May 2016.ResultsIn line with observations from the Americas and elsewhere, the single-wave Cabo Verdean ZIKV epidemic was characterized by a basic reproductive number of 1.85 (95% CI, 1.5 −2.2), with overall the attack rate of 51.1% (range 42.1 - 61.1) and observation rate of 2.7% (range 2.29 - 3.33).ConclusionCurrent herd-immunity may not be sufficient to prevent future small-to-medium epidemics in Cabo Verde. Together with a small observation rate, these results highlight the need for rapid and integrated epidemiological, molecular and genomic surveillance to tackle forthcoming outbreaks of ZIKV and other arboviruses.

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 The Uncertainties Underlying Herd Immunity against COVID-19

2020 ◽  
Author(s):  
Farid Rahimi ◽  
Amin Talebi Bezmin Abadi
Keyword(s):  
Antiviral Therapy ◽  
Case Fatality Rate ◽  
Herd Immunity ◽  
Case Fatality ◽  
Healthcare Systems ◽  
Fatality Rate ◽  
Economic Implications ◽  
Rate Transmission ◽  
The Social ◽  
And Control

Herd immunity happens when a relatively large proportion of a population becomes infected by an agent, subsequently recovers, and attains immunity against the same agent. That proportion thus indirectly protects the naïve population by preventing the spread of the infection. Herd immunity has been suggested to interrupt and control the COVID-19 pandemic. However, relying on establishing herd immunity can be catastrophic considering the virulence and lethality of SARS-CoV-2. Meanwhile our understanding of the pathogenesis, case-fatality rate, transmission routes, and antiviral therapy for COVID-19 remains limited now. Interrupting or slowing the COVID-19 transmission seems more opportune than vaccination, antiviral therapy, or herd immunity, all of which will take some time to yield. Thus, social distancing, face-masking, and hygiene are the most appropriate immediate countermeasures. Because the social fabrics, economic implications, and local demands of various nations are unique, early relaxation of restrictions may seem hasty particularly when fatality rates are high, or when the healthcare systems could be inadequate or become inundated. Conclusively, avoiding any overwhelmingly risky approach in fighting the pandemic is prudent.

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