5 research outputs found
Epidemic protection zones : centred on cases or based on connectivity?
When an exotic infectious disease invades a susceptible environment, protection
zones are enforced. Historically, such zones have been shaped as circles of
equal radius (ER), centred on the location of infected premises. Because the ER
policy seems to assume that epidemic dissemination is driven by a similar
number of secondary cases generated per primary case, it does not consider
whether local features, such as connectivity, influence epidemic dispersal. Here
we explored the efficacy of ER protection zones. By generating a geographically
explicit scenario that mimicked an actual epidemic, we created protection
zones of different geometry, comparing the cost-benefit estimates of ER protection
zones to a set of alternatives, which considered a pre-existing connecting
network (CN) â the road network. The hypothesis of similar number of cases
per ER circle was not substantiated: the number of units at risk per circle differed
up to four times among ER circles. Findings also showed that even a
small area (of <115 km2) revealed network properties. Because the CN policy
required 20% less area to be protected than the ER policy, and the CN-based
protection zone included a 23.8% greater density of units at risk/km2 than the
ER-based alternative, findings supported the view that protection zones are
likely to be less costly and more effective if they consider connecting structures,
such as road, railroad and/or river networks. The analysis of local geographical
factors (contacts, vectors and connectivity) may optimize the efficacy of control
measures against epidemics.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1865-1682ab2012ab2013 (Author correction
Connecting network properties of rapidly disseminating epizoonotics
BACKGROUND: To effectively control the geographical dissemination of infectious diseases, their properties need to be
determined. To test that rapid microbial dispersal requires not only susceptible hosts but also a pre-existing, connecting
network, we explored constructs meant to reveal the network properties associated with disease spread, which included the
road structure.
METHODS: Using geo-temporal data collected from epizoonotics in which all hosts were susceptible (mammals infected by
Foot-and-mouth disease virus, Uruguay, 2001; birds infected by Avian Influenza virus H5N1, Nigeria, 2006), two models were
compared: 1) âconnectivityâ, a model that integrated bio-physical concepts (the agentâs transmission cycle, road topology)
into indicators designed to measure networks (ânodesâ or infected sites with short- and long-range links), and 2) âcontactsâ,
which focused on infected individuals but did not assess connectivity.
RESULTS: The connectivity model showed five network properties: 1) spatial aggregation of cases (disease clusters), 2) links
among similar ânodesâ (assortativity), 3) simultaneous activation of similar nodes (synchronicity), 4) disease flows moving
from highly to poorly connected nodes (directionality), and 5) a few nodes accounting for most cases (a ââ20:800 pattern). In
both epizoonotics, 1) not all primary cases were connected but at least one primary case was connected, 2) highly
connected, small areas (nodes) accounted for most cases, 3) several classes of nodes were distinguished, and 4) the contact
model, which assumed all primary cases were identical, captured half the number of cases identified by the connectivity
model. When assessed together, the synchronicity and directionality properties explained when and where an infectious
disease spreads.
CONCLUSIONS: Geo-temporal constructs of Network Theoryâs nodes and links were retrospectively validated in rapidly
disseminating infectious diseases. They distinguished classes of cases, nodes, and networks, generating information usable
to revise theory and optimize control measures. Prospective studies that consider pre-outbreak predictors, such as
connecting networks, are recommended.The National Veterinary Research Institute, Vom, Plateau, Nigeria; the Center for Non-Linear Studies of Los Alamos
National Laboratory; and partially funded by Defense Threat Reduction Agency (DTRA) Grant CBT-09-IST-05-1-0092 (to JMF).http://www.plosone.orgab2012ab2013 (Author correction
Early network properties of the COVID-19 pandemic â the Chinese scenario
OBJECTIVES : To control epidemics, sites more affected by mortality should be identified.
METHODS : Defining epidemic nodes as areas that included both most fatalities per time unit and
connections, such as highways, geo-temporal Chinese data on the COVID-19 epidemic were investigated
with linear, logarithmic, power, growth, exponential, and logistic regression models. A z-test compared
the slopes observed.
RESULTS : Twenty provinces suspected to act as epidemic nodes were empirically investigated. Five
provinces displayed synchronicity, long-distance connections, directionality and assortativity â network
properties that helped discriminate epidemic nodes. The rank I node included most fatalities and was
activated
first. Fewer deaths were reported, later, by rank II and III nodes, while the data from rank IâIII
nodes exhibited slopes, the data from the remaining provinces did not. The power curve was the best
fitting model for all slopes. Because all pairs (rank I vs. rank II, rank I vs. rank III, and rank II vs. rank III) of
epidemic nodes differed statistically, rank IâIII epidemic nodes were geo-temporally and statistically
distinguishable.
CONCLUSIONS : The geo-temporal progression of epidemics seems to be highly structured. Epidemic
network properties can distinguish regions that differ in mortality. This real-time geo-referenced
analysis can inform both decision-makers and clinicians.http://www.elsevier.com/locate/ijidam2020Veterinary Tropical Disease
Relationship between method of anastomosis and anastomotic failure after right hemicolectomy and ileo-caecal resection: an international snapshot audit
Aim The anastomosis technique used following right-sided colonic
resection is widely variable and may affect patient outcome. This study
aimed to assess the association between leak and anastomosis technique
(stapled vs handsewn).
Method This was a prospective, multicentre, international audit
including patients undergoing elective or emergency right hemicolectomy
or ileo-caecal resection operations over a 2-month period in early 2015.
The primary outcome measure was the presence of anastomotic leak within
30 days of surgery, determined using a prespecified definition. Mixed
effects logistic regression models were used to assess the association
between leak and anastomosis method, adjusting for patient, disease and
operative cofactors, with centre included as a random-effect variable.
Results This study included 3208 patients, of whom 78.4\% (n = 2515)
underwent surgery for malignancy and 11.7\% (n = 375) underwent surgery
for Crohn's disease. An anastomosis was performed in 94.8\% (n = 3041)
of patients, which was handsewn in 38.9\% (n = 1183) and stapled in
61.1\% (n = 1858). Patients undergoing hand-sewn anastomosis were more
likely to be emergency admissions (20.5\% handsewn vs 12.9\% stapled)
and to undergo open surgery (54.7\% handsewn vs 36.6\% stapled). The
overall anastomotic leak rate was 8.1\% (245/3041), which was similar
following handsewn (7.4\%) and stapled (8.5\%) techniques (P = 0.3).
After adjustment for cofactors, the odds of a leak were higher for
stapled anastomosis (adjusted OR = 1.43; 95\% CI: 1.04-1.95; P = 0.03).
Conclusion Despite being used in lower-risk patients, stapled
anastomosis was associated with an increased anastomotic leak rate in
this observational study. Further research is needed to define patient
groups in whom a stapled anastomosis is safe