Siler et al., 1926). Widespread movements of troop s and refugees during and after World War II introduced vectors and viruses into many new areas, and this trend h as continued (Calish er, 2005 ) with the growth of global transport networks (Tatem et al., this volume, pp. 293–343). By the end of the 20th century, annual epidemics o f dengue were occurring in many parts of Central and South America (Pinheiro, 1989; Rod- riguez-Roche et al., 2005), throughout the Pacific Islands (Effler et al., 2005) and Sou th East Asia and w ith occasional o utbreaks in North Australia (Doherty et al., 1967)andAfrica. 2.2.2. Symptoms Infection with any of the four dengue serotypes may result in a spec- trum of clinical manifestations. After an incubation period of around five to six days (Siler et al., 1926; Innis et al., 1988), patients develop symptoms including joint pain, fever and headaches (Halstead, 1997; Nisalak et al., 2002). Dengue fever has unsurprisingly been mistaken for yellow fever as well as other diseases including influenza, measles, typhoid and malaria (Hare, 1898; Siler et al., 1926; Lopez-Correa et al., 1979; Holmes et al., 1998). Although highly uncomfortable, dengue fever is rarely fatal and survivors appear to have lifelong immunity to the homologous serotype. Far more serious is dengue haemorrhagic fever (DHF), where addi- tional symptoms develop, including haemorrhaging and shock. The mortality from DHF can exceed 30% if appropriate care is unavailable. The most significant risk factor for DHF is when secondary infection with a different serotype occurs in people who have already had, and recovered from, a primary dengue infection. It is suggested that virus infection is enhanced by the presence of pre-existing heterotypic anti- bodies (Halstead, 1970, 1988; Halstead et al., 1980). Under this ‘anti- body-dependent enhancement’ hypothesis, pre-existing antibodies bind to the h eterotypic dengue virus p articles but fail to n eutralise them once cross-reactive antibodies have decayed below a certain level. These in- fectious an tibody–virus complexes bind to receptors on macrophages more easily, resulting in a higher level of viral uptake. The presence of antibodies to a heterotypic serotype has been demonstrated to increase the ability of d engue viru s particles to infect monocytes in both in vitro D.J. ROGERS ET AL.190 Plate 6.7 Risk map for yellow fever. This risk map is the average of 100 bootstrap models each based on a sample of 300 presence and 300 absence pixels selected at random with replacement from the training set for this disease. Risk is on a probability scale from zero to 1.0. Probabilities from 0.0 to 0.49 are coloured green (darker to lighter) and indicate conditions not suitable for the disease (i.e. predicted absence of disease). Probabilities from 0.50 to 1.0 are coloured yellow through to dark red, indicating conditions increasingly suitable for the disease. The database observations of presence are indicated by the blue dots and the WHO 2003 map for yellow fever by the thick black outline. Plate 6.7 (continued) Plate 6.8 Risk map f or dengue. This risk map is the average of 100 bootstrap models each based on a sample of 900 presenc e and 900 absence pixels selected at random with replacement from the training set for this disease. Risk is on a probability scale from zero to 1.0. Probabilities from 0.0 t o 0.49 a re coloured green (darker t o lighter) and indicate con ditions not suitable for the disease (i.e. predicted absence of dise ase ). Probabilities fro m 0.50 to 1.0 are co loured yellow through to dark red, indicating c onditions increasingly suitable for the disease. The database observations of presence are indicated by the blue dots and the WHO 2003 map for dengue by the thick black outline. Plate 6.8 (continued) Global Epidemiology, Ecology and Control of Soil-Transmitted Helminth Infections S. Brooker 1 , A.C.A. Clements 1,2 and D.A.P. Bundy 3 1 Department of Infectious and Tropical Disease, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK 2 Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College, Norfolk Place, London W2 1PG, UK 3 Human Development Division, The World Bank, Washington DC 20433, USA Abstract 221 1. Introduction. . 222 2. Transmission Dynamics and the Environment 224 3. Ecological Correlates. . 227 4. Predicting Distributions 231 5. Urbanization . 232 6. Global Control Strategies 234 7. Control Applications of GIS/RS . . 237 8. Global Distributions. . . 243 9. Predicted Numbers of Infections . 246 10. The Future . . 250 Acknowledgements. . . 252 References . . 252 ABSTRACT Soil-transmitted helminth (STH) infections are among the most prev- alent of chronic human infections worldwide. Based on the demon- strable impact on child development, there is a global commitment to finance and implement control strategies with a focus on school-based ADVANCES IN PARASITOLOGY VOL 62 ISSN: 0065-308X $35.00 DOI: 10.1016/S0065-308X(05)62007-6 Copyright r 2006 Elsevier Ltd. All rights of reproduction in any form reserved 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 1020304050 Temperature (°C) Temperature (°C) Proportion surviving (a) (b) 0 20 40 60 80 100 120 140 0 1020304050 Development time (days) Model fit T. trichiura Model fit A. lumbricoides Model fit hookworm Observed T. trichiura Observed A. lumbricoides Observed hookworm Figure 1 Relationship between temperature and (a) hookworm survival and (b) development duration. Points indicate experimental data (Seamster, 1950; Beer, 1973; Nwosu, 1978; Udonsi and Atata, 1987) and lines are fits derived from fractional polynomials analyses. Regres- sion details: parasite survival y ¼ 0.884+(À22.88x À0.5 )+(À7.73ln(x)); A. lumbricoides duration y ¼ 8.601+(À63.718x À2 )+2.526x À3 ; T. trichiura duration y ¼ 26.079+41209.68x À2 +(À1715.02x À2 ); hookworm duration y ¼ 3.701+40.88x À2 +(À46.18x À2 ). S. BROOKER ET AL.226 . with a focus on school-based ADVANCES IN PARASITOLOGY VOL 62 ISSN: 0 06 5-3 08X $35.00 DOI: 10.10 16/ S0 06 5-3 08X(05 )62 00 7 -6 Copyright r 20 06 Elsevier Ltd. All rights of reproduction in any form reserved 0 0.1 0.2 0.3 0.4 0.5 0 .6 0.7 0.8 0.9 1 0. Control of Soil-Transmitted Helminth Infections S. Brooker 1 , A.C.A. Clements 1,2 and D.A.P. Bundy 3 1 Department of Infectious and Tropical Disease, London School of Hygiene and Tropical Medicine,. Symptoms Infection with any of the four dengue serotypes may result in a spec- trum of clinical manifestations. After an incubation period of around five to six days (Siler et al., 19 26; Innis et