Disease Ecology Research Group
We are interested in quantifying the ecological parameters important for the transmission and control of endemic infections of humans. We use and derive mathematical and statistical results in infectious disease epidemiology and population biology to analyse data collected through routine surveillance and intervention studies. We collaborate with several organisations that work in the field, including the World Health Organisation, UNAIDS and the International Trachoma Initiative. At present we have projects focusing on polio persistence, the transmission and control of sexually transmitted infections, models of trachoma transmission and methods to estimate global statistics on HIV/AIDS.
Polio persistence
The World Health Organisation committed to global polio eradication in 1988, since when the number of paralytic cases has fallen from about 350,000 to just 1,255 in 2004. However, endemic transmission continues in South East Asia and West Africa despite mass vaccination, with subsequent export of infection to countries with poor vaccine coverage leading to significant outbreaks. We are investigating the causes of polio persistence using routine surveillance data collected on cases of acute flaccid paralysis.
People
Nicholas Grassly, Christophe Fraser, Helen Jenkins
Collaborating Institutes
World Health Organisation, National Polio Surveillance Project (NPSP)-India, National Primary Health Care Development Agency-Nigeria
Selected publications
Jenkins HE, Aylward RB, Gasasira A, Donnelly CA, Koleosho-Adelekan T, Abanida EA and Grassly NC The effectiveness of immunization against polio in Nigeria. New Engl J Med 2008. 359: 1666-1674. [full text]
Grassly NC, Wenger J, Durrani S, et al. Protective efficacy of a monovalent oral type 1 poliovirus vaccine: a case-control study. Lancet 2007. 369:1356-1362.
Grassly NC, Fraser C, Wenger J, et al. New strategies for the elimination of polio from India. Science 2006. 314:1150 - 1153. [full text link available from personal webpage]
Trachoma
Repeated infection of the eyes with Chlamydia trachomatis leads to inflammation, scarring and eventually blindness. Trachoma remains the leading cause of infectious blindness despite being easily treatable with a single oral dose of antibiotics. The WHO has committed to the global eradication of blindness due to infection with C. trachomatis (but not the infection itself) by 2020 through a combined treatment and prevention strategy. Central to the success of this strategy is an understanding of the transmission dynamics of trachoma and the surprisingly loose relationship between infection and disease. We are therefore developing models of the transmission of infection and the host immune response that will be fit to data on the prevalence of both clinically diagnosed disease and bacterial infection estimated through quantitative and qualitative PCR.
People
Isobel Blake, Nicholas Grassly, Maria-Gloria Basanez,
Collaborating Institutes
International Trachoma Initiative, London School of Hygiene and Tropical Medicine
Selected publications
Blake IM, Burton MJ, Bailey R, Solomon AW, West SK, Munoz B, Mabey D, Gambhir M, Basanez M-G & Grassly NC (2009) Estimating household and community transmission of ocular Chlamydia trachomatis. PLoS Negl Trop Dis e401. doi:10.1371/journal.pntd.0000401 [full text]
Grassly NC, Ward ME, Ferris S, Mabey DC & Bailey RL (2008) The natural history of trachoma infection and disease in a Gambian cohort with frequent follow-up. PLoS Negl Trop Dis 2: e341. [full text]
Gambhir M, Basanez M-G, Turner F, Kumaresan J, Grassly N. Trachoma: transmission, infection, and control. Lancet Infect Dis 2007;7:420-27. [full text]
Sexually Transmitted Infections
The incidence of sexually transmitted infections (STIs) is strongly dependent on the sexual behaviour of individuals and the network of sexual partners that connect them. However, the biology and aetiology of these infections is also important, and can interact with behaviour and population processes to produce complex disease dynamics. We are interested in disentangling these processes to allow correct interpretation of trends in the incidence of STIs and the success or failure of control programmes to be identified.
People
Nicholas Grassly, Geoff Garnett, Christophe Fraser, Helen Ward
Collaborating Institutes
US Centers for Disease Control and Prevention (CDC), The Joint United Nations Programme on HIV/AIDS (UNAIDS), UK Health Protection Agency (HPA)
Selected publications
Grassly NC, Fraser C & Garnett GP. Host immunity and synchronized epidemics of syphilis across the United States. Nature433, 417-421 (2005). [pdf]
Grassly NC et al. Modelling emerging HIV epidemics: the role of injecting drug use and sexual transmission in the Russian Federation, China and India. International Journal of Drug Policy14, 25-43. (2003). [pdf]
Global statistics on HIV/AIDS
Estimates of the number of people infected with HIV, deaths from AIDS, orphans due to AIDS and other measures of disease burden that can reasonably be compared across countries are central to planning and advocacy by national and international organisations. In many cases, the challenge is to produce valid statistics from patchy and often biased surveillance data. We have been central to the development of methods to produce national and global statistics on HIV/AIDS through the UNAIDS Reference Group on Estimates, Modelling and Projections, now co-ordinated by Peter White in this department. We are continuing to work on these methods, with a particular focus on correctly characterising the uncertainty in national and global statistics.
People
Nicholas Grassly, Geoff Garnett, Simon Gregson, Peter White
Collaborating Institutes
UNAIDS, WHO
Selected publications
Grassly NC and Timaeus IM. Methods to estimate the number of orphans as a result of AIDS and other causes in sub-Saharan Africa J AIDS39, 365-75 (2005)
Grassly NC and Garnett GP. The future of the HIV pandemic Bull WHO83, 378-82. (2005) [pdf]
Walker N, Grassly NC, Garnett GP, Stanecki KA & Ghys PD. Estimating the global burden of HIV/AIDS: what do we really know about the HIV pandemic? Lancet 363, 2180-5 (2004)
Grassly NC et al. Uncertainty in estimates of HIV/AIDS: the estimation and application of plausibility bounds. Sex. Transm. Infect. 2004. 80: i31-i38. [pdf]
Stover J et al. Can we reverse the HIV/AIDS pandemic with an expanded response? Lancet 360, 73-7 (2002)
