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Article ; Online: Parasite-induced shifts in host movement may explain the transient coexistence of high- and low-pathogenic disease strains.

Fofana, Abdou Moutalab / Hurford, Amy

2022 Volume 35, Issue 8, Page(s) 1072–1086

Abstract: Many parasites induce decreased host movement, known as lethargy, which can impact disease spread and the evolution of virulence. Mathematical models have investigated virulence evolution when parasites cause host death, but disease-induced decreased ... ...

Abstract	Many parasites induce decreased host movement, known as lethargy, which can impact disease spread and the evolution of virulence. Mathematical models have investigated virulence evolution when parasites cause host death, but disease-induced decreased host movement has received relatively less attention. Here, we consider a model where, due to the within-host parasite replication rate, an infected host can become lethargic and shift from a moving to a resting state, where it can die. We find that when the lethargy and disease-induced mortality costs to the parasites are not high, then evolutionary bistability can arise, and either moderate or high virulence can evolve depending on the initial virulence and the magnitude of mutation. These results suggest, firstly, the coexistence of strains with different virulence, which may explain the transient coexistence of low- and high-pathogenic strains of avian influenza viruses, and secondly, that medical interventions to treat the symptoms of lethargy or prevent disease-induced host deaths can result in a large jump in virulence and the rapid evolution of high virulence. In complement to existing results that show bistability when hosts are heterogeneous at the population level, we show that evolutionary bistability may arise due to transmission heterogeneity at the individual host level.
MeSH term(s)	Animals ; Biological Evolution ; Host-Parasite Interactions/genetics ; Lethargy ; Models, Biological ; Parasites/genetics ; Virulence/genetics
Language	English
Publishing date	2022-07-05
Publishing country	Switzerland
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	1465318-7
ISSN	1420-9101 ; 1010-061X
ISSN (online)	1420-9101
ISSN	1010-061X
DOI	10.1111/jeb.14053
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Article: Parasite‐induced shifts in host movement may explain the transient coexistence of high‐ and low‐pathogenic disease strains

Fofana, Abdou Moutalab / Hurford, Amy

Journal of evolutionary biology. 2022 Aug., v. 35, no. 8

2022

Abstract	Many parasites induce decreased host movement, known as lethargy, which can impact disease spread and the evolution of virulence. Mathematical models have investigated virulence evolution when parasites cause host death, but disease‐induced decreased host movement has received relatively less attention. Here, we consider a model where, due to the within‐host parasite replication rate, an infected host can become lethargic and shift from a moving to a resting state, where it can die. We find that when the lethargy and disease‐induced mortality costs to the parasites are not high, then evolutionary bistability can arise, and either moderate or high virulence can evolve depending on the initial virulence and the magnitude of mutation. These results suggest, firstly, the coexistence of strains with different virulence, which may explain the transient coexistence of low‐ and high‐pathogenic strains of avian influenza viruses, and secondly, that medical interventions to treat the symptoms of lethargy or prevent disease‐induced host deaths can result in a large jump in virulence and the rapid evolution of high virulence. In complement to existing results that show bistability when hosts are heterogeneous at the population level, we show that evolutionary bistability may arise due to transmission heterogeneity at the individual host level.
Keywords	avian influenza ; complement ; death ; evolution ; mortality ; mutation ; parasites ; virulence
Language	English
Dates of publication	2022-08
Size	p. 1072-1086.
Publishing place	John Wiley & Sons, Ltd
Document type	Article
Note	JOURNAL ARTICLE
ZDB-ID	1465318-7
ISSN	1420-9101 ; 1010-061X
ISSN (online)	1420-9101
ISSN	1010-061X
DOI	10.1111/jeb.14053
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Is SARS-CoV-2 elimination or mitigation best? Regional and disease characteristics determine the recommended strategy

Martignoni, Maria M. / Arino, Julien / Hurford, Amy

medRxiv

Abstract: Public health responses to the COVID-19 pandemic varied across the world. Some countries (e.g., mainland China, New Zealand, and Taiwan) implemented elimination strategies involving strict travel measures and periods of rigorous non-pharmaceutical ... ...

Abstract	Public health responses to the COVID-19 pandemic varied across the world. Some countries (e.g., mainland China, New Zealand, and Taiwan) implemented elimination strategies involving strict travel measures and periods of rigorous non-pharmaceutical interventions (NPIs) in the community, aiming to achieve periods with no disease spread; while others (e.g., many European countries and the United States of America) implemented mitigation strategies involving less strict NPIs for prolonged periods, aiming to limit community spread. Travel measures and community NPIs have high economic and social costs, and there is a need for guidelines that evaluate the appropriateness of an elimination or mitigation strategy in regional contexts. To guide decisions, we identify key criteria and provide indicators and visualizations to help answer each question. Considerations include determining whether disease elimination is: (1) necessary to ensure health care provision; (2) feasible from an epidemiological point of view; and (3) cost effective when considering, in particular, the economic costs of travel measures and treating infections. We discuss our recommendations by considering the regional and economic variability of Canadian provinces and territories, and the epidemiological characteristics of different SARS-CoV-2 variants.
Keywords	covid19
Language	English
Publishing date	2024-02-07
Publisher	Cold Spring Harbor Laboratory Press
Document type	Article ; Online
DOI	10.1101/2024.02.01.24302169
Database	COVID19

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Article: Resource and seasonality drive interspecific variability in simulations from a dynamic energy budget model.

Mariño, Joany / Dufour, Suzanne C / Hurford, Amy / Récapet, Charlotte

Conservation physiology

2023 Volume 11, Issue 1, Page(s) coad013

Abstract: Animals show a vast array of phenotypic traits in time and space. Such variation patterns have traditionally been described as ecogeographical rules; for example, the tendency of size and clutch size to increase with latitude (Bergmann's and Lack's rules, ...

Abstract	Animals show a vast array of phenotypic traits in time and space. Such variation patterns have traditionally been described as ecogeographical rules; for example, the tendency of size and clutch size to increase with latitude (Bergmann's and Lack's rules, respectively). Despite considerable research into these variation patterns and their consequences for biodiversity and conservation, the processes behind trait variation remain controversial. Here, we show how food variability, largely set by climate and weather, can drive interspecific trait variation by determining individual energy input and allocation trade-offs. Using a dynamic energy budget (DEB) model, we simulated different food environments, as well as interspecific variability in the parameters for energy assimilation, mobilization and allocation to soma. We found that interspecific variability is greater when the resource is non-limiting in both constant and seasonal environments. Our findings further show that individuals can reach larger biomass and greater reproductive output in a seasonal environment than in a constant environment of equal average resource due to the peaks of food surplus. Our results agree with the classical patterns of interspecific trait variation and provide a mechanistic understanding that supports recent hypotheses which explain them: the resource and the eNPP (net primary production during the growing season) rules. Due to the current alterations to ecosystems and communities, disentangling the mechanisms of trait variation is increasingly important to understand and predict biodiversity dynamics under climate change, as well as to improve conservation strategies.
Language	English
Publishing date	2023-03-30
Publishing country	England
Document type	Journal Article
ZDB-ID	2721508-8
ISSN	2051-1434
ISSN	2051-1434
DOI	10.1093/conphys/coad013
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Article: Extensive SARS-CoV-2 testing reveals BA.1/BA.2 asymptomatic rates and underreporting in school children.

Martignoni, Maria M / Mohammadi, Zahra / Loredo-Osti, J Concepción / Hurford, Amy

Canada communicable disease report = Releve des maladies transmissibles au Canada

2023 Volume 49, Issue 4, Page(s) 155–165

Abstract: Background: Case underreporting during the coronavirus disease 2019 (COVID-19) pandemic has been a major challenge to the planning and evaluation of public health responses. School children were often considered a less vulnerable population and ... ...

Abstract	Background: Case underreporting during the coronavirus disease 2019 (COVID-19) pandemic has been a major challenge to the planning and evaluation of public health responses. School children were often considered a less vulnerable population and underreporting rates may have been particularly high. In January 2022, the Canadian province of Newfoundland and Labrador (NL) was experiencing an Omicron variant outbreak (BA.1/BA.2 subvariants) and public health officials recommended that all returning students complete two rapid antigen tests (RATs) to be performed three days apart. Methods: To estimate the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we asked parents and guardians to report the results of the RATs completed by K-12 students (approximately 59,000 students) using an online survey. Results: When comparing the survey responses with the number of cases and tests reported by the NL testing system, we found that one out of every 4.3 (95% CI, 3.1-5.3) positive households were captured by provincial case count, with 5.1% positivity estimated from the RAT results and 1.2% positivity reported by the provincial testing system. Of positive test results, 62.9% (95% CI, 44.3-83.0) were reported for elementary school students, and the remaining 37.1% (95% CI, 22.7-52.9) were reported for junior high and high school students. Asymptomatic infections were 59.8% of the positive cases. Given the low survey participation rate (3.5%), our results may suffer from sample selection biases and should be interpreted with caution. Conclusion: The underreporting ratio is consistent with ratios calculated from serology data and provides insights into infection prevalence and asymptomatic infections in school children; a currently understudied population.
Language	English
Publishing date	2023-04-01
Publishing country	Canada
Document type	Journal Article
ZDB-ID	1146585-2
ISSN	1188-4169
ISSN	1188-4169
DOI	10.14745/ccdr.v49i04a08
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Article ; Online: Importation models for travel-related SARS-CoV-2 cases reported in Newfoundland and Labrador during the COVID-19 pandemic

Mohammadi, Zahra / Cojocaru, Monica / Arino, Julien / Hurford, Amy

medRxiv

Abstract: During the COVID-19 pandemic there was substantial variation between countries in the severity of the travel restrictions implemented suggesting a need for better importation models. Data to evaluate the accuracy of importation models is available for ... ...

Abstract	During the COVID-19 pandemic there was substantial variation between countries in the severity of the travel restrictions implemented suggesting a need for better importation models. Data to evaluate the accuracy of importation models is available for the Canadian province of Newfoundland and Labrador (NL; September 2020 to June 2021) as arriving travelers were frequently tested for SARS-CoV-2 and travel-related cases were reported. Travel volume to NL was estimated from flight data, and travel declaration forms completed at entry to Canada, and at entry to NL during the pandemic. We found that during the pandemic travel to NL decreased by 82%, the percentage of travelers arriving from Qu&eacutebec decreased (from 14 to 4%), and from Alberta increased (from 7 to 17%). We derived and validated an epidemiological model predicting the number of travelers testing positive for SARS-CoV-2 after arrival in NL, but found that statistical models with less description of SARS-CoV-2 epidemiology, and with parameters fitted from the validation data more accurately predicted the daily number of travel-related cases reported in NL originating from Canada (R<sup>2</sup> = 0.55, ΔAICc = 137). Our results highlight the importance of testing travelers and reporting travel-related cases as these data are needed for importation models to support public health decisions.
Keywords	covid19
Language	English
Publishing date	2023-06-12
Publisher	Cold Spring Harbor Laboratory Press
Document type	Article ; Online
DOI	10.1101/2023.06.08.23291136
Database	COVID19

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Article ; Online: When host populations move north, but disease moves south: Counter-intuitive impacts of climate change on disease spread

Moran, E. Joe / Martignoni, Maria M. / Lecomte, Nicolas / Leighton, Patrick / Hurford, Amy

Theor Ecol. 2023 Mar., v. 16, no. 1 p.13-19

2023

Abstract: Empirical observations and mathematical models show that climate warming can lead to the northern (or, more generally, poleward) spread of host species ranges and their corresponding diseases. Here, we consider an unexpected possibility whereby climate ... ...

Abstract	Empirical observations and mathematical models show that climate warming can lead to the northern (or, more generally, poleward) spread of host species ranges and their corresponding diseases. Here, we consider an unexpected possibility whereby climate warming facilitates disease spread in the opposite direction to the directional shift in the host species range. To explore this possibility, we consider two host species, both susceptible to a disease, but spatially isolated due to distinct thermal niches, and where prior to climate warming the disease is endemic in the northern species only. Previous theoretical results show that species distributions can lag behind species thermal niches when climate warming occurs. As such, we hypothesize that climate warming may increase the overlap between northern and southern host species ranges, due to the northern species lagging behind its thermal tolerance limit. To test our hypothesis, we simulate climate warming as a reaction-diffusion equation model with a Susceptible-Infected (SI) epidemiological structure, for two competing species with distinct temperature-dependent niches. We show that climate warming, by shifting both species niches northwards, can facilitate the southward spread of disease, due to increased range overlap between the two populations. As our model is general, our findings may apply to viral, bacterial, and prion diseases that do not have thermal tolerance limits and are inextricably linked to their hosts distributions, such as the spread of rabies from arctic to red foxes.
Keywords	climate ; climate change ; disease transmission ; equations ; heat tolerance ; hosts ; models ; prions ; rabies
Language	English
Dates of publication	2023-03
Size	p. 13-19.
Publishing place	Springer Netherlands
Document type	Article ; Online
ZDB-ID	2391025-2
ISSN	1874-1746 ; 1874-1738
ISSN (online)	1874-1746
ISSN	1874-1738
DOI	10.1007/s12080-022-00551-z
Database	NAL-Catalogue (AGRICOLA)

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Article: Modelling the impact of travel restrictions on COVID-19 cases in Newfoundland and Labrador.

Hurford, Amy / Rahman, Proton / Loredo-Osti, J Concepción

Royal Society open science

2021 Volume 8, Issue 6, Page(s) 202266

Abstract: In many jurisdictions, public health authorities have implemented travel restrictions to reduce coronavirus disease 2019 (COVID-19) spread. Policies that restrict travel within countries have been implemented, but the impact of these restrictions is not ... ...

Abstract	In many jurisdictions, public health authorities have implemented travel restrictions to reduce coronavirus disease 2019 (COVID-19) spread. Policies that restrict travel within countries have been implemented, but the impact of these restrictions is not well known. On 4 May 2020, Newfoundland and Labrador (NL) implemented travel restrictions such that non-residents required exemptions to enter the province. We fit a stochastic epidemic model to data describing the number of active COVID-19 cases in NL from 14 March to 26 June. We predicted possible outbreaks over nine weeks, with and without the travel restrictions, and for contact rates 40-70% of pre-pandemic levels. Our results suggest that the travel restrictions reduced the mean number of clinical COVID-19 cases in NL by 92%. Furthermore, without the travel restrictions there is a substantial risk of very large outbreaks. Using epidemic modelling, we show how the NL COVID-19 outbreak could have unfolded had the travel restrictions not been implemented. Both physical distancing and travel restrictions affect the local dynamics of the epidemic. Our modelling shows that the travel restrictions are a plausible reason for the few reported COVID-19 cases in NL after 4 May.
Language	English
Publishing date	2021-06-16
Publishing country	England
Document type	Journal Article
ZDB-ID	2787755-3
ISSN	2054-5703
ISSN	2054-5703
DOI	10.1098/rsos.202266
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Article ; Online: Downsizing of COVID-19 contact tracing in highly immune populations.

Martignoni, Maria M / Renault, Josh / Baafi, Joseph / Hurford, Amy

PloS one

2022 Volume 17, Issue 6, Page(s) e0268586

Abstract: Contact tracing is a key component of successful management of COVID-19. Contacts of infected individuals are asked to quarantine, which can significantly slow down (or prevent) community spread. Contact tracing is particularly effective when infections ... ...

Abstract	Contact tracing is a key component of successful management of COVID-19. Contacts of infected individuals are asked to quarantine, which can significantly slow down (or prevent) community spread. Contact tracing is particularly effective when infections are detected quickly, when contacts are traced with high probability, when the initial number of cases is low, and when social distancing and border restrictions are in place. However, the magnitude of the individual contribution of these factors in reducing epidemic spread and the impact of population immunity (due to either previous infection or vaccination), in determining contact tracing outputs is not fully understood. We present a delayed differential equation model to investigate how the immunity status and the relaxation of social distancing requirements affect contact tracing practices. We investigate how the minimal contact tracing efficiency required to keep an outbreak under control depends on the contact rate and on the proportion of immune individuals. Additionally, we consider how delays in outbreak detection and increased case importation rates affect the number of contacts to be traced daily. We show that in communities that have reached a certain immunity status, a lower contact tracing efficiency is required to avoid a major outbreak, and delayed outbreak detection and relaxation of border restrictions do not lead to a significantly higher risk of overwhelming contact tracing. We find that investing in testing programs, rather than increasing the contact tracing capacity, has a larger impact in determining whether an outbreak will be controllable. This is because early detection activates contact tracing, which will slow, and eventually reverse exponential growth, while the contact tracing capacity is a threshold that will easily become overwhelmed if exponential growth is not curbed. Finally, we evaluate quarantine effectiveness in relation to the immunity status of the population and for different viral variants. We show that quarantine effectiveness decreases with increasing proportion of immune individuals, and increases in the presence of more transmissible variants. These results suggest that a cost-effective approach is to establish different quarantine rules for immune and nonimmune individuals, where rules should depend on viral transmissibility after vaccination or infection. Altogether, our study provides quantitative information for contact tracing downsizing in vaccinated populations or in populations that have already experienced large community outbreaks, to guide COVID-19 exit strategies.
MeSH term(s)	COVID-19/epidemiology ; COVID-19/prevention & control ; Contact Tracing/methods ; Disease Outbreaks/prevention & control ; Humans ; Quarantine ; SARS-CoV-2
Language	English
Publishing date	2022-06-10
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2267670-3
ISSN	1932-6203 ; 1932-6203
ISSN (online)	1932-6203
ISSN	1932-6203
DOI	10.1371/journal.pone.0268586
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Extensive SARS-CoV-2 testing reveals BA.1/BA.2 asymptomatic rates and underreporting in school children

Martignoni, Maria M / Mohammadi, Zahra / Loredo-Osti, JC / Hurford, Amy

medRxiv

Abstract: Case underreporting during the COVID-19 pandemic has been a major challenge to the planning and evaluation of public health responses. Inconsistent underreporting can undermine effective risk assessment due to high uncertainty in predicted future ... ...

Abstract	Case underreporting during the COVID-19 pandemic has been a major challenge to the planning and evaluation of public health responses. Inconsistent underreporting can undermine effective risk assessment due to high uncertainty in predicted future scenarios. Underreporting rates have been particularly high among children and youth, given that asymptomatic school children were often considered a less vulnerable population. In January 2022, the Canadian province of Newfoundland and Labrador (NL) was experiencing an Omicron variant outbreak (BA.1/BA.2 subvariants) and public health officials recommended that all students returning to elementary, junior high, and high schools (~59,452 students) complete two rapid antigen tests (RATs) to be performed three days apart. To estimate the prevalence of SARS-CoV-2, we asked parents and guardians to report the results of the RATs completed by K-12 students using an online survey, and to specify the students9 school level and if students with positive RAT results had symptoms. When comparing the survey responses with the number of cases and tests reported by the NL testing system, we found that 1 out of every 4.3 (3.1-5.3) positive households were captured by provincial case count, with 5.1% positivity estimated from the RAT results, and 1.2% positivity reported by the provincial testing system. The survey data indicate that a higher percentage of SARS-CoV-2 cases were found in elementary schools, with 62.9% of positive cases (95% CI: 44.3%, 83.0%) reported from elementary school students, and the remaining 37.1% (95% CI: 22.7%, 52.9%) reported from junior high and high school students. Asymptomatic infections were 59.8% of the positive cases, with no significant difference between asymptomatic rates in elementary schools (60.8%) or in junior high and high schools (58.1%). Given the low survey participation rate (3.5%), our results may suffer from sample selection biases, and should be interpreted with caution. Nonetheless, our estimate of the underreporting ratio is consistent with ratios calculated from serology data, and our study provides insights into infection prevalence and asymptomatic infections in school children, a currently understudied population.
Keywords	covid19
Language	English
Publishing date	2023-01-18
Publisher	Cold Spring Harbor Laboratory Press
Document type	Article ; Online
DOI	10.1101/2023.01.15.23284579
Database	COVID19

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