Imperial College London

ProfessorNicholasGrassly

Faculty of MedicineSchool of Public Health

Prof of Infectious Disease & Vaccine Epidemiology
 
 
 
//

Contact

 

+44 (0)20 7594 3264n.grassly Website

 
 
//

Location

 

G36Medical SchoolSt Mary's Campus

//

Summary

 

Publications

Publication Type
Year
to

114 results found

O'Reilly KM, Chauvin C, Aylward RB, Maher C, Okiror S, Wolff C, Nshmirimana D, Donnelly CA, Grassly NCet al., 2011, A statistical model of the international spread of wild poliovirus in Africa used to predict and prevent outbreaks, PLoS Med, Vol: 8, Pages: 1-10, ISSN: 1549-1676

BACKGROUND: Outbreaks of poliomyelitis in African countries that were previously free of wild-type poliovirus cost the Global Polio Eradication Initiative US$850 million during 2003-2009, and have limited the ability of the program to focus on endemic countries. A quantitative understanding of the factors that predict the distribution and timing of outbreaks will enable their prevention and facilitate the completion of global eradication. METHODS AND FINDINGS: Children with poliomyelitis in Africa from 1 January 2003 to 31 December 2010 were identified through routine surveillance of cases of acute flaccid paralysis, and separate outbreaks associated with importation of wild-type poliovirus were defined using the genetic relatedness of these viruses in the VP1/2A region. Potential explanatory variables were examined for their association with the number, size, and duration of poliomyelitis outbreaks in 6-mo periods using multivariable regression analysis. The predictive ability of 6-mo-ahead forecasts of poliomyelitis outbreaks in each country based on the regression model was assessed. A total of 142 genetically distinct outbreaks of poliomyelitis were recorded in 25 African countries, resulting in 1-228 cases (median of two cases). The estimated number of people arriving from infected countries and <5-y childhood mortality were independently associated with the number of outbreaks. Immunisation coverage based on the reported vaccination history of children with non-polio acute flaccid paralysis was associated with the duration and size of each outbreak, as well as the number of outbreaks. Six-month-ahead forecasts of the number of outbreaks in a country or region changed over time and had a predictive ability of 82%. CONCLUSIONS: Outbreaks of poliomyelitis resulted primarily from continued transmission in Nigeria and the poor immunisation status of populations in neighbouring countries. From 1 January 2010 to 30 June 2011, reduced transmission in Nigeria and in

Journal article

Gambhir M, Basanez MG, Blake IM, Grassly Net al., 2010, Modelling trachoma for control programmes, Modelling Parasite Transmission and Control, Editors: Michael, Spear, Publisher: Austin, Texas: Landes Bioscience, ISBN: 9781441960641

Book chapter

Blake IM, Burton MJ, Solomon AW, West SK, Basanez M-G, Gambhir M, Bailey RL, Mabey DCW, Grassly NCet al., 2010, Targeting Antibiotics to Households for Trachoma Control, PLOS NEGLECTED TROPICAL DISEASES, Vol: 4, ISSN: 1935-2735

Journal article

Jenkins HE, Aylward RB, Gasasira A, Donnelly CA, Mwanza M, Corander J, Garnier S, Chauvin C, Abanida E, Pate MA, Adu F, Baba M, Grassly NCet al., 2010, Implications of a Circulating Vaccine-Derived Poliovirus in Nigeria., NEW ENGLAND JOURNAL OF MEDICINE, Vol: 362, Pages: 2360-2369, ISSN: 0028-4793

Journal article

Grassly NC, Jafari H, Bahl S, Durrani S, Wenger J, Sutter RW, Aylward RBet al., 2010, Asymptomatic Wild-Type Poliovirus Infection in India among Children with Previous Oral Poliovirus Vaccination, JOURNAL OF INFECTIOUS DISEASES, Vol: 201, Pages: 1535-1543, ISSN: 0022-1899

Journal article

Gambhir M, Basanez M-G, Blake IM, Grassly NCet al., 2010, Modelling Trachoma for Control Programmes, MODELLING PARASITE TRANSMISSION AND CONTROL, Vol: 673, Pages: 141-156, ISSN: 0065-2598

Journal article

Ribas L, Li MS, Doddington BJ, Robert J, Seidel JA, Kroll JS, Zimmerman LB, Grassly NC, Garner TW, Fisher MCet al., 2009, Expression Profiling the Temperature-Dependent Amphibian Response to Infection by Batrachochytrium dendrobatidis, PLOS One, Vol: 4, ISSN: 1932-6203

Amphibians are experiencing a panzootic of unprecedented proportions caused by the emergence of Batrachochytrium dendrobatidis (Bd). However, all species are not equally at risk of infection, and risk is further modified by environmental variables, specifically temperature. In order to understand how, and when, hosts mount a response to Bd we analysed infection dynamics and patterns of gene expression in the model amphibian species Silurana (Xenopus) tropicalis. Mathematical modelling of infection dynamics demonstrate the existence of a temperature-dependent protective response that is largely independent of the intrinsic growth-rate of Bd. Using temporal expression-profiling by microarrays and qRT-PCR, we characterise this response in the main amphibian lymphoid tissue, the spleen. We demonstrate that clearance of Bd at the host-optimal temperature is not clearly associated with an adaptive immune response, but rather is correlated with the induction of components of host innate immunity including the expression of genes that are associated with the production of the antimicrobial skin peptide preprocareulein (PPCP) as well as inflammatory responses. We find that adaptive immunity appears to be lacking at host-optimal temperatures. This suggests that either Bd does not stimulate, or suppresses, adaptive immunity, or that trade-offs exist between innate and adaptive limbs of the amphibian immune system. At cold temperatures, S. tropicalis loses the ability to mount a PPCP-based innate response, and instead manifests a more pronounced inflammatory reaction that is characterised by the production of proteases and higher pathogen burdens. This study demonstrates the temperature-dependency of the amphibian response to infection by Bd and indicates the influence that changing climates may exert on the ectothermic host response to pathogens.

Journal article

Grassly NC, Jafari H, Bahl S, Durrani S, Wenger J, Sutter RW, Aylward RBet al., 2009, Mucosal Immunity after Vaccination with Monovalent and Trivalent Oral Poliovirus Vaccine in India, JOURNAL OF INFECTIOUS DISEASES, Vol: 200, Pages: 794-801, ISSN: 0022-1899

Journal article

Fraser C, Donnelly CA, Cauchemez S, Hanage WP, Van Kerkhove MD, Hollingsworth TD, Griffin J, Baggaley RF, Jenkins HE, Lyons EJ, Jombart T, Hinsley WR, Grassly NC, Balloux F, Ghani AC, Rambaut A, Ferguson NMet al., 2009, Influenza: Making Privileged Data Public Response, SCIENCE, Vol: 325, Pages: 1072-1073, ISSN: 0036-8075

Journal article

Fraser C, Donnelly CA, Cauchemez S, Hanage WP, Van Kerkhove MD, Hollingsworth TD, Griffin J, Baggaley RF, Jenkins HE, Lyons EJ, Jombart T, Hinsley WR, Grassly NC, Balloux F, Ghani AC, Ferguson NM, Rambaut A, Pybus OG, Lopez-Gatell H, Alpuche-Aranda CM, Bojorquez Chapela I, Palacios Zavala E, Espejo Guevara DM, Checchi F, Garcia E, Hugonnet S, Roth Cet al., 2009, Pandemic Potential of a Strain of Influenza A (H1N1): Early Findings, SCIENCE, Vol: 324, Pages: 1557-1561, ISSN: 0036-8075

Journal article

Gambhir M, Basanez M-G, Burton MJ, Solomon AW, Bailey RL, Holland MJ, Blake IM, Donnelly CA, Jabr I, Mabey DC, Grassly NCet al., 2009, The Development of an Age-Structured Model for Trachoma Transmission Dynamics, Pathogenesis and Control, PLOS Neglected Tropical Diseases, Vol: 3, ISSN: 1935-2735

Background: Trachoma, the worldwide leading infectious cause of blindness, is due to repeated conjunctival infection with Chlamydia trachomatis. The effects of control interventions on population levels of infection and active disease can be promptly measured, but the effects on severe ocular sequelae require long-term monitoring. We present an age-structured mathematical model of trachoma transmission and disease to predict the impact of interventions on the prevalence of blinding trachoma.Methodology/Principal Findings: The model is based on the concept of multiple reinfections leading to progressive conjunctival scarring, trichiasis, corneal opacity and blindness. It also includes aspects of trachoma natural history, such as an increasing rate of recovery from infection and a decreasing chlamydial load with subsequent infections that depend upon a (presumed) acquired immunity that clears infection with age more rapidly. Parameters were estimated using maximum likelihood by fitting the model to pre-control infection prevalence data from hypo-, meso- and hyperendemic communities from The Gambia and Tanzania. The model reproduces key features of trachoma epidemiology: 1) the age-profile of infection prevalence, which increases to a peak at very young ages and declines at older ages; 2) a shift in this prevalence peak, toward younger ages in higher force of infection environments; 3) a raised overall profile of infection prevalence with higher force of infection; and 4) a rising profile, with age, of the prevalence of the ensuing severe sequelae (trachomatous scarring, trichiasis), as well as estimates of the number of infections that need to occur before these sequelae appear.Conclusions/Significance: We present a framework that is sufficiently comprehensive to examine the outcomes of the A (antibiotic) component of the SAFE strategy on disease. The suitability of the model for representing population-level patterns of infection and disease sequelae is discussed in

Journal article

Blake IM, Burton MJ, Bailey RL, Solomon AW, West S, Munoz B, Holland MJ, Mabey DCW, Gambhir M, Basanez M-G, Grassly NCet al., 2009, Estimating Household and Community Transmission of Ocular Chlamydia trachomatis, PLOS NEGLECTED TROPICAL DISEASES, Vol: 3, ISSN: 1935-2735

Journal article

Grassly NC, Ward ME, Ferris S, Mabey DC, Bailey RLet al., 2008, The Natural History of Trachoma Infection and Disease in a Gambian Cohort with Frequent Follow-Up, PLOS NEGLECTED TROPICAL DISEASES, Vol: 2, ISSN: 1935-2735

Journal article

Jenkins HE, Aylward RB, Gasasira A, Donnelly CA, Abanida EA, Koleosho-Adelekan T, Grassly NCet al., 2008, Effectiveness of immunization against paralytic poliomyelitis in Nigeria, NEW ENGLAND JOURNAL OF MEDICINE, Vol: 359, Pages: 1666-U111, ISSN: 0028-4793

Journal article

Grassly NC, Fraser C, 2008, Mathematical models of infectious disease transmission, NATURE REVIEWS MICROBIOLOGY, Vol: 6, Pages: 477-487, ISSN: 1740-1526

Journal article

Cooper A, Grassly N, Rambaut A, 2007, Using Molecular Data to Estimate Divergence Times, Palaeobiology II, Pages: 532-534, ISBN: 9780632051496

Book chapter

Grassly NC, Wenger J, Aylward RB, 2007, Potent questions about India's polio vaccine - Response, SCIENCE, Vol: 318, Pages: 914-+, ISSN: 0036-8075

Journal article

Grassly NC, Wenger J, Aylward RB, 2007, Response [6], Science, Vol: 318, Pages: 914-916, ISSN: 0036-8075

Journal article

Grassly NC, Wenger J, Bahl S, Sutter RW, Aylward RBet al., 2007, Protective efficacy of a monovalent oral type 1 poliovirus vaccine - Reply, LANCET, Vol: 370, Pages: 129-130, ISSN: 0140-6736

Journal article

Gambhir M, Basanez M-G, Turner F, Kumaresan J, Grassly NCet al., 2007, Trachoma: transmission, infection, and control, LANCET INFECTIOUS DISEASES, Vol: 7, Pages: 420-427, ISSN: 1473-3099

Journal article

Grassly NC, Wenger J, Durrani S, 2007, Protective efficacy of a monovalent oral type 1 poliovirus vaccine: a case-control study (vol 369, pg 1356, 2007), LANCET, Vol: 369, Pages: 1790-1790, ISSN: 0140-6736

Journal article

Grassly NC, Wenger J, Durrani S, Bahl S, Deshpande JM, Sutter RW, Heymann DL, Aylward RBet al., 2007, Protective efficacy of a monovalent oral type 1 poliovirus vaccine: a case-control study, LANCET, Vol: 369, Pages: 1356-1362, ISSN: 0140-6736

Journal article

Grassly NC, Fraser C, Wenger J, Deshpande JM, Sutter RW, Heymann DL, Aylward RBet al., 2006, New strategies for the elimination of polio from India, SCIENCE, Vol: 314, Pages: 1150-1153, ISSN: 0036-8075

Journal article

Grassly NC, Fraser C, 2006, Seasonal Infectious Disease Epidemiology, Proceedings of the Royal Society of London B, Vol: FirstCite Early Online Publish

Journal article

Stover J, Walker N, Grassly NC, Marston Met al., 2006, Projecting the demographic impact of AIDS and the number of people in need of treatment: updates to the Spectrum Projection Package, SEXUALLY TRANSMITTED INFECTIONS, Vol: 82, Pages: III45-III50, ISSN: 1368-4973

Journal article

Brown T, Grassly NC, Garnett G, Stanecki Ket al., 2006, Improving projections at the country level: the UNAIDS Estimation and Projection Package 2005, SEXUALLY TRANSMITTED INFECTIONS, Vol: 82, Pages: III34-III40, ISSN: 1368-4973

Journal article

Brown T, Grossly NC, Garnett G, Stanecki Ket al., 2006, Improving projections at the country level: the UNAIDS Estimation and Projection Package 2005, SEX TRANSM INFECT, Vol: 82, Pages: 34-40, ISSN: 1368-4973

Background: UNAIDS has developed the Estimation and Projection Package (EPP) as a tool for national programmes to use for making national estimates and short term projections of HIV prevalence. EPP provides direct input to Spectrum, which produces incidence, deaths, and AIDS impacts.Methods: The latest version, EPP 2005, includes substantial methodological improvements over the previous version. These include: (1) parallel, but unique, interfaces for generalised and concentrated epidemics; (2) use of maximum likelihood fitting procedures; (3) a new procedure, known as level fits, adjusting for expansion of national surveillance systems into lower prevalence sites; (4) provisions for handling turnover in at-risk populations, including the reassignment of HIV positive former members to lower risk populations; and (5) user-defined calibration to HIV prevalence levels from general population or other epidemiological surveys.Results: Following regional training in mid 2005, this new version has been applied by many national programmes to make their end of 2005 estimates of HIV infections. UNAIDS has combined these national estimates to form the 2005 global HIV and AIDS estimates.Conclusion: EPP 2005 is a substantial improvement over previous versions, forming a solid base for the next round of modifications. Proposed modifications for that next version are presented for the reader's information.

Journal article

Grassly NC, Timaeus IM, 2005, Methods to estimate the number of orphans as a result of AIDS and other causes in sub-Saharan Africa, JAIDS-JOURNAL OF ACQUIRED IMMUNE DEFICIENCY SYNDROMES, Vol: 39, Pages: 365-375, ISSN: 1525-4135

Journal article

Grassly NC, Garnett GP, 2005, The future of the HIV pandemic, BULLETIN OF THE WORLD HEALTH ORGANIZATION, Vol: 83, Pages: 378-382, ISSN: 0042-9686

Journal article

Grassly NC, Fraser C, Garnett GP, 2005, Host immunity and synchronized epidemics of syphilis across the United States, NATURE, Vol: 433, Pages: 417-421, ISSN: 0028-0836

Journal article

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://wlsprd.imperial.ac.uk:80/respub/WEB-INF/jsp/search-html.jsp Request URI: /respub/WEB-INF/jsp/search-html.jsp Query String: id=00334932&limit=30&person=true&page=3&respub-action=search.html