Estimating prevalence trends in adult gonorrhoea and syphilis in low- and middle-income countries with the Spectrum-STI model: results for Zimbabwe and Morocco from 1995 to 2016.
To develop a tool for estimating national trends in adult prevalence of sexually transmitted infections by low- and middle-income countries, using standardised, routinely collected programme indicator data.



The Spectrum-STI model fits time trends in the prevalence of active syphilis through logistic regression on prevalence data from antenatal clinic-based surveys, routine antenatal screening and general population surveys where available, weighting data by their national coverage and representativeness. Gonorrhoea prevalence was fitted as a moving average on population surveys (from the country, neighbouring countries and historic regional estimates), with trends informed additionally by urethral discharge case reports, where these were considered to have reasonably stable completeness. Prevalence data were adjusted for diagnostic test performance, high-risk populations not sampled, urban/rural and male/female prevalence ratios, using WHO's assumptions from latest global and regional-level estimations. Uncertainty intervals were obtained by bootstrap resampling.



Estimated syphilis prevalence (in men and women) declined from 1.9% (95% CI 1.1% to 3.4%) in 2000 to 1.5% (1.3% to 1.8%) in 2016 in Zimbabwe, and from 1.5% (0.76% to 1.9%) to 0.55% (0.30% to 0.93%) in Morocco. At these time points, gonorrhoea estimates for women aged 15-49 years were 2.5% (95% CI 1.1% to 4.6%) and 3.8% (1.8% to 6.7%) in Zimbabwe; and 0.6% (0.3% to 1.1%) and 0.36% (0.1% to 1.0%) in Morocco, with male gonorrhoea prevalences 14% lower than female prevalence.



This epidemiological framework facilitates data review, validation and strategic analysis, prioritisation of data collection needs and surveillance strengthening by national experts. We estimated ongoing syphilis declines in both Zimbabwe and Morocco. For gonorrhoea, time trends were less certain, lacking recent population-based surveys.
Avenir Health, Geneva, Switzerland.
Eline L
EL
Korenromp
Avenir Health, Glastonbury, Connecticut, USA.
Guy
G
Mahiané
London, UK.
Jane
J
Rowley
Malawi-Liverpool Wellcome Trust, Blantyre, Malawi.
Nico
N
Nagelkerke
Weill Cornell Medical College-Qatar, Cornell University, Doha, Qatar.
Laith
L
Abu-Raddad
Skin & Genito-Urinary Medicine Clinic, Harare, Zimbabwe.
Francis
F
Ndowa
Ministry of Health, Direction de l'Epidémiologie & Service de Maladies Sexuellement Transmissibles, Rabat, Morocco.
Amina
A
El-Kettani
UNAIDS Morocco Country Office, Rabat, Morocco.
Houssine
H
El-Rhilani
London School of Hygiene and Tropical Medicine, London, UK.
Philippe
P
Mayaud
London School of Hygiene and Tropical Medicine, London, UK.
R Matthew
RM
Chico
Avenir Health, Glastonbury, Connecticut, USA.
Carel
C
Pretorius
Avenir Health, Glastonbury, Connecticut, USA.
Kendall
K
Hecht
Department of Reproductive Health and Research, World Health Organization, Geneva, Switzerland.
Teodora
T
Wi
D000328:Adult; D005260:Female; D006069:Gonorrhea / Q000453:epidemiology*; D049673:History, 20th Century; D049674:History, 21st Century; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D009018:Morocco / Q000453:epidemiology; D011159:Population Surveillance / Q000379:methods*; D015995:Prevalence; D013587:Syphilis / Q000453:epidemiology*; D015030:Zimbabwe / Q000453:epidemiology
AFRICA; GONORRHOEA; MATHEMATICAL MODEL; SURVEILLANCE; SYPHILIS