Jiafeng Pan

A stochastic differential equation SIS epidemic model

In this paper we extend the classical susceptible-infected-susceptible epidemic model from a deterministic framework to a stochastic one and formulate it as a stochastic differential equation (SDE) for the number of infectious individuals

Human Papillomavirus Prevalence and Herd Immunity after Introduction of Vaccination Program, Scotland, 2009-2013

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Cumulative and temporal associations between antimicrobial prescribing and community-associated Clostridium difficile infection: population-based case control study using administrative data

. We then prove that this SDE has a unique global positive solution

Human Papilloma Virus (HPV) Oral Prevalence in Scotland (HOPSCOTCH): a feasibility study in dental settings

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Use of HPV testing for cervical screening in vaccinated women—Insights from the SHEVa (Scottish HPV Prevalence in Vaccinated Women) study

and establish conditions for extinction and persistence of

Reduction in colposcopy workload and associated clinical activity following HPV catch-up vaccination programme in Scotland : an ecological study

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Risk stratification of cervical disease using detection of human papillomavirus (HPV) E4 protein and cellular MCM protein in clinical liquid based cytology samples

. We discuss perturbation by stochastic noise. In the case of persistence we show the existence of a stationary distribution and derive expressions for its mean and variance. The results are illustrated by computer simulations, including two examples based on real-life diseases.

Improving predictive asthma algorithms with modelled environment data for Scotland: an observational cohort study protocol

Prevalence was reduced, and early evidence indicates herd immunity.

The SIS epidemic model with Markovian switching

Background Community-associated Clostridium difficile infection (CA-CDI; defined as cases without prior hospitalization in the previous 12 weeks who were either tested outside of hospital or tested within 2 days of admission to hospital) is a major public health problem. This study estimates the magnitude of the association between temporal and cumulative prescribing of antimicrobials in primary care and CA-CDI. Methods Three national patient-level datasets, covering CDI cases, community prescriptions and hospitalizations, were linked by the NHS Scotland unique patient identifier, the Community Health Index (CHI). All validated cases of CDI from August 2010 to July 2013 were extracted and up to six population-based controls were matched to each case from the CHI register for Scotland. Statistical analysis used conditional logistic regression. Results The 1446 unique cases of CA-CDI were linked with 7964 age-, sex- and location-matched controls. Cumulative exposure to any antimicrobial in the previous 6 months has a monotonic dose-response association with CA-CDI. Individuals with more than 28 DDDs to any antimicrobial (19.9% of cases) had an OR of 4.4 (95% CI 3.4-5.6) compared with those unexposed. Individuals exposed to 29+ DDDs of high-risk antimicrobials (cephalosporins, clindamycin, co-amoxiclav or fluoroquinolones) had an OR of 17.9 (95% CI 7.6-42.2). Elevated CA-CDI risk following high-risk antimicrobial exposure was greatest in the first month (OR = 12.5, 95% CI 8.9-17.4), but was still present 4-6 months later (OR = 2.6, 95% CI 1.7-3.9). Cases exposed to 29+ DDDs had prescription patterns more consistent with repeated therapeutic courses, using different antimicrobials, than long-term prophylactic use. Conclusions This analysis demonstrated temporal and dose-response associations between CA-CDI risk and antimicrobials, with an impact of exposure to high-risk antimicrobials remaining 4-6 months later.

Parameter estimation for the stochastic SIS epidemic model

The purpose of this study was to test the feasibility of undertaking a full population investigation into the prevalence, incidence, and persistence of oral Human Papilloma Virus (HPV) in Scotland via dental settings. Male and female patients aged 16–69 years were recruited by Research Nurses in 3 primary care and dental outreach teaching centres and 2 General Dental Practices (GDPs), and by Dental Care Teams in 2 further GDPs. Participants completed a questionnaire (via an online tablet computer or paper) with socioeconomic, lifestyle, and sexual history items; and were followed up at 6-months for further questionnaire through appointment or post/online. Saline oral gargle/rinse samples, collected at baseline and follow-up, were subject to molecular HPV genotyping centrally. 1213 dental patients were approached and 402 individuals consented (participation rate 33.1%). 390 completed the baseline questionnaire and 380 provided a baseline oral specimen. Follow-up rate was 61.6% at 6 months. While recruitment was no different in Research Nurse vs Dental Care Team models the Nurse model ensured more rapid recruitment. There were relatively few missing responses in the questionnaire and high levels of disclosure of risk behaviours (99% answered some of the sexual history questions). Data linkage of participant data to routine health records including HPV vaccination data was successful with 99.1% matching. Oral rinse/gargle sample collection and subsequent HPV testing was feasible. Preliminary analyses found over 95% of samples to be valid for molecular HPV detection prevalence of oral HPV infection of 5.5% (95%CI 3.7, 8.3). It is feasible to recruit and follow-up dental patients largely representative / reflective of the wider population, suggesting it would be possible to undertake a study to investigate the prevalence, incidence, and determinants of oral HPV infection in dental settings.