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SUMMARY:Metapopulation epidemic model fitted to spatiotemporal spread of r
ubella in Japan\, 2012-13
DTSTART;VALUE=DATE-TIME:20180712T003000Z
DTEND;VALUE=DATE-TIME:20180712T010000Z
DTSTAMP;VALUE=DATE-TIME:20220814T125616Z
UID:indico-contribution-56-64@conferences.maths.unsw.edu.au
DESCRIPTION:Speakers: Hiroshi Nishiura (Hokkaido University)\n*Background:
* Japan experienced a nationwide rubella epidemic from 2012 to 2013\, most
ly in urban prefectures with large population sizes. The present study aim
ed to capture the spatiotemporal patterns of rubella using a parsimonious
metapopulation epidemic model and examine the potential usefulness of spat
ial vaccination.\n\n*Methodology/Principal Findings:* A metapopulation epi
demic model in discrete time and space was devised and applied to rubella
notification data from 2012 to 2013. Linearly approximating growth pattern
s in six different time periods using the particle Markov chain Monte Carl
o method yielded estimates of effective reproduction numbers of 1.37 (95%
CrI: 1.12\, 1.77) and 1.37 (95% CrI: 1.24\, 1.48) in Tokyo and Osaka group
s\, respectively\, during the growing phase of the epidemic in 2013. The r
ubella epidemic in 2012 involved substantial uncertainties in its paramete
r estimates and forecasts. We examined multiple scenarios of spatial vacci
nation with coverages of 1%\, 3% and 5% for all of Japan to be distributed
in different combinations of prefectures. Scenarios indicated that vaccin
ating the top six populous urban prefectures (i.e.\, Tokyo\, Kanagawa\, Os
aka\, Aichi\, Saitama and Chiba) could potentially be more effective than
random allocation. However\, greater uncertainty was yielded by initial se
eds of infectious individuals\, initial fraction susceptible and stochasti
city.\n\n*Conclusions:* While the forecast in 2012 was accompanied by broa
d uncertainties\, a narrower uncertainty bound of parameters and reliable
forecast were achieved during the greater rubella epidemic in 2013. By bet
ter capturing the underlying epidemic dynamics\, possibly with age-depende
nt and prefecture-specific susceptibility distributions\, spatial vaccinat
ion could potentially be substantially discriminated from random vaccinati
on.\n\nhttps://conferences.maths.unsw.edu.au/event/2/contributions/64/
LOCATION:University of Sydney New Law School/--101
URL:https://conferences.maths.unsw.edu.au/event/2/contributions/64/
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SUMMARY:A general framework to account for unobserved heterogeneity in epi
demiology
DTSTART;VALUE=DATE-TIME:20180712T010000Z
DTEND;VALUE=DATE-TIME:20180712T013000Z
DTSTAMP;VALUE=DATE-TIME:20220814T125616Z
UID:indico-contribution-56-170@conferences.maths.unsw.edu.au
DESCRIPTION:Speakers: Gabriela Gomes (Liverpool School of Tropical Medicin
e\, UK\, and Centro de Investigação em Biodiversidade e Recursos Genéti
cos\, Universidade do Porto\, Portugal)\nUnobserved heterogeneity was intr
oduced in 1920 as a modifier of individual hazards. The concept was termed
frailty in demography to describe variation in individual longevity [1]\,
and has been incorporated in methods for survival analysis. As the fraile
st individuals are removed earlier from a heterogeneous group\, mean hazar
ds appear to decrease over time – cohort selection – leading to some o
f the most elusive effects in population science. Despite the accumulation
of documented fallacies induced by cohort selection\, the issue remains l
argely overlooked. I will expose the ubiquity of the phenomenon and propos
e a general framework to infer and compare trait distributions\, with exam
ples of current interest in epidemiology and related disciplines: \n(1) Va
ccines appear less effective in high-incidence settings. Are they\, really
[2]? \n(2) What is the real effect of *Wolbachia* on mosquito susceptibil
ity to dengue viruses [3]? \n(3) As populations of bacteria are exposed to
antibiotics\, their mortality rates decline due to selection for noninher
ited resistance4. How much does this phenomenon share with what has been d
escribed in human demography [1]? \n(4) What does cohort selection add to
the debate between neutral and niche theories of biodiversity? \n\n[1] Vau
pel JW\, Manton KG\, Stallard E (1979) Impact of heterogeneity in individu
al frailty on the dynamics of mortality. *Demography* 16: 439-454.\n[2] Go
mes MGM\, Gordon SB\, Lalloo DG (2016) Clinical trials: the mathematics of
falling vaccine efficacy with rising disease incidence. *Vaccine* 34: 300
7-3009.\n[3] King JG\, Souto-Maior C\, Sartori L\, Maciel-de-Freitas R\, G
omes MGM (2018) Variation in *Wolbachia* effects on *Aedes* mosquitoes is
a key determinant of invasiveness and vectorial capacity. *Nat Commun* (in
press).\n[4] Balaban NQ\, Merrin J\, Chait R\, Kowalik L\, Leibler S (200
4) Bacterial persistence as a phenotypic switch. *Science* 305: 1622-1625.
\n\nhttps://conferences.maths.unsw.edu.au/event/2/contributions/170/
LOCATION:University of Sydney New Law School/--101
URL:https://conferences.maths.unsw.edu.au/event/2/contributions/170/
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SUMMARY:Vector feeding preference annihilates backward bifurcation and red
uces endemicity
DTSTART;VALUE=DATE-TIME:20180712T020000Z
DTEND;VALUE=DATE-TIME:20180712T023000Z
DTSTAMP;VALUE=DATE-TIME:20220814T125616Z
UID:indico-contribution-56-187@conferences.maths.unsw.edu.au
DESCRIPTION:Speakers: Rocio Marilyn Caja Rivera (University of Notre Dame)
\nWe propose and analyze a mathematical model of a vector-borne disease th
at includes vector feeding preference for carrier hosts and intrinsic incu
bation in hosts. Analysis of the model reveals the following novel results
. We show theoretically and numerically that vector feeding preference for
carrier hosts plays an important role for the existence of both the endem
ic equilibria and backward bifurcation when the basic reproduction number
$R_0$ is less than one. Moreover\, by increasing the vector feeding prefer
ence value\, backward bifurcation is eliminated and endemic equilibria for
hosts and vectors are diminished.\n\nTherefore\, the vector protects itse
lf and this benefits the host. As an example of these phenomena\, we prese
nt a case of Andean Cutaneous Leishmaniasis (ACL) in Peru. We use paramete
r values from previous studies\, primarily from Peru to introduce bifurcat
ion diagrams and compute global sensitivity of $R_0$ in order to quantify
and understand the effects of the important parameters of our model. Globa
l sensitivity analysis via partial rank correlation coefficient (PRCC) sho
ws that $R_0$ is highly sensitive to both sandflies feeding preference and
mortality rate of sandflies.\n\nhttps://conferences.maths.unsw.edu.au/eve
nt/2/contributions/187/
LOCATION:University of Sydney New Law School/--101
URL:https://conferences.maths.unsw.edu.au/event/2/contributions/187/
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SUMMARY:Modelling Human African Trypanosomiasis and the effects of domesti
c animals on transmission
DTSTART;VALUE=DATE-TIME:20180712T013000Z
DTEND;VALUE=DATE-TIME:20180712T020000Z
DTSTAMP;VALUE=DATE-TIME:20220814T125616Z
UID:indico-contribution-56-193@conferences.maths.unsw.edu.au
DESCRIPTION:Speakers: Meghan Burke (Kennesaw State University)\nThe Human
African Trypanosomiasis (HAT) parasite\, which causes African Sleeping Sic
kness\, is transmitted by the tsetse fly as a vector. It has several poss
ible hosts\, including wild and domestic animals\, who are not as negative
ly impacted by the disease as the human host. It has long been assumed th
at because domestic animals can be hosts for the parasite\, that keeping d
omestic animals near human populations increases the spread of the disease
. However\, several parameters found in the literature\, including the sh
orter lifespan of the male vector\, and the female vector's preference for
domestic animals\, made us question this assumption. \n\n We developed a
differential equation compartmental model to examine whether increasing th
e domestic animal population can be used to deflect the infection from hum
ans and reduce its impact. We have used numerical simulations and have ex
amined the Basic Reproduction Number ($R_0$) for the model to quantify the
effect of the domestic animal population on human infection. These analy
ses allow us to propose novel methods of controlling the impact of the dis
ease on humans.\n\nhttps://conferences.maths.unsw.edu.au/event/2/contribut
ions/193/
LOCATION:University of Sydney New Law School/--101
URL:https://conferences.maths.unsw.edu.au/event/2/contributions/193/
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