Journal Article > ResearchFull Text
Public Health Action. 2020 September 21; Volume 10; DOI:10.5588/pha.19.0074
Makelele JPK, Ade S, Takarinda KC, Manzi M, Gil Cuesta J, et al.
Public Health Action. 2020 September 21; Volume 10; DOI:10.5588/pha.19.0074
Setting: In 1995, a rapid response project for humanitarian and medical emergencies, including outbreak responses, named ‘Pool d’Urgence Congo’ (PUC), was implemented in the Democratic Republic of Congo by Médecins Sans Frontières.
Objective: To assess the outcomes of cholera and measles outbreak alerts that were received in the PUC surveillance system between 2016 and 2018.
Design: This was a retrospective cross-sectional study.
Results: Overall, 459 outbreak alerts were detected, respectively 69% and 31% for cholera and measles. Of these, 32% were actively detected and 68% passively detected. Most alerts (90%) required no intervention and 10% of alerts had an intervention. There were 25% investigations that were not carried out despite thresholds being met; 17% interventions were not performed, the main reported reason being PUC operational capacity was exceeded. Confirmed cholera and measles outbreaks that met an investigation threshold comprised respectively 90% and 76% of alerts; 59% of measles investigations were followed by a delayed outbreak response of 14 days (n = 10 outbreaks).
Conclusion: Some alerts for cholera and measles outbreaks that were detected in the PUC system did not lead to a response even when required; the main reported reason was limited operational capacity to respond to all of them.
Objective: To assess the outcomes of cholera and measles outbreak alerts that were received in the PUC surveillance system between 2016 and 2018.
Design: This was a retrospective cross-sectional study.
Results: Overall, 459 outbreak alerts were detected, respectively 69% and 31% for cholera and measles. Of these, 32% were actively detected and 68% passively detected. Most alerts (90%) required no intervention and 10% of alerts had an intervention. There were 25% investigations that were not carried out despite thresholds being met; 17% interventions were not performed, the main reported reason being PUC operational capacity was exceeded. Confirmed cholera and measles outbreaks that met an investigation threshold comprised respectively 90% and 76% of alerts; 59% of measles investigations were followed by a delayed outbreak response of 14 days (n = 10 outbreaks).
Conclusion: Some alerts for cholera and measles outbreaks that were detected in the PUC system did not lead to a response even when required; the main reported reason was limited operational capacity to respond to all of them.
Journal Article > Short ReportAbstract
Pediatr Infect Dis J. 2013 July 30; Volume 33 (Issue 1); DOI:10.1097/INF.0b013e3182a6e1cd
Moons P, Thallinger M
Pediatr Infect Dis J. 2013 July 30; Volume 33 (Issue 1); DOI:10.1097/INF.0b013e3182a6e1cd
During an outbreak of measles in a refugee camp in Ethiopia, 9 patients (age range 4 months to 18 years) were diagnosed with subcutaneous emphysema. Incidence of this rare complication of measles in this refugee camp was higher than previously reported. We hypothesize that the high incidence is most likely related to poor physical state of the refugee population with high rates of malnutrition.
Journal Article > ResearchFull Text
BMC Public Health. 2019 August 22; Volume 19 (Issue 1); DOI:10.1186/s12889-019-7500-z
Keating P, Carrion Martin AI, Blake A, Lechevalier P, Uzzeni F, et al.
BMC Public Health. 2019 August 22; Volume 19 (Issue 1); DOI:10.1186/s12889-019-7500-z
BACKGROUND:
Measles continues to circulate in the Democratic Republic of Congo, and the country suffered from several important outbreaks over the last 5 years. Despite a large outbreak starting in the former province of Katanga in 2010 and the resulting immunization activities, another outbreak occurred in 2015 in this same region. We conducted measles seroprevalence surveys in four health zones (HZ) in the former Katanga Province in order to assess the immunity against measles in children 6 months to 14 years after the 2015 outbreak.
METHODS:
We conducted multi-stage cluster surveys stratified by age group in four HZs, Kayamba, Malemba-Nkulu, Fungurume, and Manono. The age groups were 6-11 months, 12-59 months, and 5-14 years in Kayamba and Malemba-Nkulu, 6-59 months and 5-14 years in Manono and Fungurume. The serological status was measured on dried capillary blood spots collected systematically along with vaccination status (including routine Extended Program of Immunization (EPI), and supplementary immunization activities (SIAs)) and previous self-reported history of suspected measles.
RESULTS:
Overall seroprevalence against measles was 82.7% in Kayamba, 97.6% in Malemba-Nkulu, 83.2% in Manono, and 74.4% in Fungurume, and it increased with age in all HZs. It was 70.7 and 93.8% in children 12-59 months in Kayamba and Malemba-Nkulu, and 49.8 and 64.7% in children 6-59 months in Fungurume and Manono. The EPI coverage was low but varied across HZ. The accumulation of any type of vaccination against measles resulted in an overall vaccine coverage (VC) of at least 85% in children 12-59 months in Kayamba and Malemba-Nkulu, 86.1 and 74.8% in children 6-59 months in Fungurume and Manono. Previous measles infection in 2015-early 2016 was more frequently reported in children aged 12-59 months or 6-59 months (depending on the HZ).
CONCLUSION:
The measured seroprevalence was consistent with the events that occurred in these HZs over the past few years. Measles seroprevalence might prove a valuable source of information to help adjust the timing of future SIAs and prioritizing support to the EPI in this region as long as the VC does not reach a level high enough to efficiently prevent epidemic flare-ups.
Measles continues to circulate in the Democratic Republic of Congo, and the country suffered from several important outbreaks over the last 5 years. Despite a large outbreak starting in the former province of Katanga in 2010 and the resulting immunization activities, another outbreak occurred in 2015 in this same region. We conducted measles seroprevalence surveys in four health zones (HZ) in the former Katanga Province in order to assess the immunity against measles in children 6 months to 14 years after the 2015 outbreak.
METHODS:
We conducted multi-stage cluster surveys stratified by age group in four HZs, Kayamba, Malemba-Nkulu, Fungurume, and Manono. The age groups were 6-11 months, 12-59 months, and 5-14 years in Kayamba and Malemba-Nkulu, 6-59 months and 5-14 years in Manono and Fungurume. The serological status was measured on dried capillary blood spots collected systematically along with vaccination status (including routine Extended Program of Immunization (EPI), and supplementary immunization activities (SIAs)) and previous self-reported history of suspected measles.
RESULTS:
Overall seroprevalence against measles was 82.7% in Kayamba, 97.6% in Malemba-Nkulu, 83.2% in Manono, and 74.4% in Fungurume, and it increased with age in all HZs. It was 70.7 and 93.8% in children 12-59 months in Kayamba and Malemba-Nkulu, and 49.8 and 64.7% in children 6-59 months in Fungurume and Manono. The EPI coverage was low but varied across HZ. The accumulation of any type of vaccination against measles resulted in an overall vaccine coverage (VC) of at least 85% in children 12-59 months in Kayamba and Malemba-Nkulu, 86.1 and 74.8% in children 6-59 months in Fungurume and Manono. Previous measles infection in 2015-early 2016 was more frequently reported in children aged 12-59 months or 6-59 months (depending on the HZ).
CONCLUSION:
The measured seroprevalence was consistent with the events that occurred in these HZs over the past few years. Measles seroprevalence might prove a valuable source of information to help adjust the timing of future SIAs and prioritizing support to the EPI in this region as long as the VC does not reach a level high enough to efficiently prevent epidemic flare-ups.
Journal Article > CommentaryFull Text
PLOS Med. 2013 November 5; Volume 10 (Issue 11); DOI:10.1371/journal.pmed.1001544
Minetti A, Bopp C, Fermon F, Francois G, Grais RF, et al.
PLOS Med. 2013 November 5; Volume 10 (Issue 11); DOI:10.1371/journal.pmed.1001544
Andrea Minetti and colleagues compare measles outbreak responses from the Democratic Republic of the Congo and Malawi and argue that outbreak response strategies should be tailored to local measles epidemiology. Please see later in the article for the Editors' Summary.
Technical Report > Survey
Ouedraogo P, Simons E, Grellety E
2023 November 1
English
Français
INTRODUCTION
Since April 15, 2023, fighting erupted in Sudan between the army led by General Abdel Fattah al-Burhan and the paramilitary Rapid Support Forces (RSF) under the command of General Mohamed Hamdan Dogolo, known as Hemeti. This war has caused a major humanitarian crisis in Sudan, with violent fighting spreading throughout the country, particularly in Darfur, and aggravating pre-existing inter-community tensions.
By the end of March, almost 30,000 civilians had fled to Chad in search of safety. By September 2023, according to data from the United Nations High Commissioner for Refugees (UNHCR), clashes between military and paramilitary forces had driven more than 420,000 people to flee to Chad in successive waves, of whom around 327,000 had settled in the Ouaddaï province. Chadian refugees and returnees live in very precarious conditions, with limited access to primary healthcare, water and food. Little recent data is available on the mortality, nutritional status, and vaccination coverage of refugee populations in camps in eastern Chad, particularly in Toumtouma, Ourang and Arkoum camps. The results of these surveys are essential for Médecins Sans Frontières (MSF) to better plan its humanitarian interventions, coordinate effectively with other actors, and communicate about the refugee crisis in eastern Chad.
METHODOLOGY
Three cross-sectional surveys were carried out, the first with systematic random sampling in Toumtouma camp from August 7 to 13, and the next two with cluster random geospatial sampling in Ourang camp from August 17 to 22 and Arkoum camp from August 30 to September 4, 2023. Each survey covered retrospective mortality, frequency and type of violent events experienced, nutritional status of children aged 6 to 59 months, and measles vaccination coverage among children aged 6 months to 14 years. The recall period ran from January 1 to the day of the survey, i.e., a minimum of 210, 228 and 241 days respectively. Two phases were considered: 1) the pre-crisis phase (Toumtouma: January 1 - March 14, 2023 / Ourang and Arkoum: January 1 - April 14, 2023) and 2) the crisis phase (Toumtouma: March 15 - day of survey / Ourang and Arkoum: April 15 - day of survey). In Toumtouma camp, the crisis phase started earlier due to inter-community tensions that erupted end of March in West Darfur and drove important population displacements towards Chad.
RESULTS
Retrospective mortality: In Toumtouma camp, of the 1,032 households included (i.e., 6,372 people), 59.7% were refugees, 35.9% returnees and 4.4% displaced persons. The crude mortality rate (CMR) was significantly higher in phase 2 (CMR: 0.58 deaths/10,000 people/day [95% CI: 0.43 - 0.74]) than in phase 1 (CMR: 0.20 deaths/10,000 people/day [95% CI: 0.07 - 0.33]). Eighty-nine percent of those who died were men. Violence (77%; n=48) was the main cause of death reported, followed by diarrhea (6%; n=4) and respiratory infection (5%; n=3). Among the deaths, 68% occurred in their town or village of origin, 21% during displacement and 11% in an unknown location. Most people who died came from El Geneina (40%), Tandulti (35%) and Umm Dam (16%) in Darfur.
In Ourang camp, of the 1032 households included (i.e., 6302 people), 99.0% were refugees and 1.0% returnees. The CMR was significantly higher in phase 2 (CMR: 2.25 deaths/10,000 people/day [95% CI: 1.77 - 2.74]) than in phase 1 (CMR: 0.11 deaths/10,000 people/day [95% CI: 0.02 - 0.20]). Eighty-three percent of those who died were men (3.88 deaths/10,000 people/day [95% CI: 3.01 - 4.76] in phase 2). Violence (82%; n=147) was the main cause of death reported, followed by measles (5%; n=9). Among the deaths, 69% occurred in their town or village of origin, 25% during displacement and 6% in Adre, Chad. Most people who died came from El Geneina (96%) in Darfur.
In Arkoum camp, of the 1029 households included (i.e., 5324 people), 98.4% were refugees, 1.3% displaced and 0.4% returnees. The CMR was significantly higher in phase 2 (CMR: 0.67 deaths/10,000 people/day [95% CI: 0.46 - 0.89]) than in phase 1 (CMR: 0.15 deaths/10,000 people/day [95% CI: 0.03 - 0.26]). Seventy-seven percent of those who died were men; the mortality rate among men was 1.14 [95% CI: 0.72 - 1.55] in the second phase. Violence (50%; n=28) was the main cause of death reported, followed by diarrhea (16%; n=9). Among the deaths, 52% occurred in their town or village of origin, 27% during displacement, 5% after their arrival in Chad and 16% in an unknown location. Most people who died came from Mistre (54%) and Kongu (29%) in Darfur.
Frequency and main causes of violence: Among households in Toumtouma, Ourang and Arkoum camps, the overall frequency of violence was 3.3%, 11.7% and 4.4% respectively. The main types of violence were beatings (71.0% in Toumtouma, 71.1% in Ourang, and 79.7% in Arkoum), and shootings (27.1% in Toumtouma, 34.7% in Ourang, and 15.1% in Arkoum).
Prevalence of acute malnutrition: Among children aged 6-59 months, the prevalence of global acute malnutrition (GAM) according to MUAC and/or bilateral oedema was 5.5% [95% CI: 4.1 - 7.5] in Toumtouma, 11.3% [95% CI: 9.2 - 13.8] in Ourang, and 11.6% [95% CI: 9.5 - 14.5] in Arkoum camp. Rates of severe acute malnutrition (SAM) were 2.3% [95% CI: 1.4 - 3.6] in Toumtouma, 4.8% [95% CI: 3.6 - 6.4] in Ourang, and 4.6% [95% CI: 3.4 - 6.3] in Arkoum.
Measles vaccination: Measles vaccination coverage among children aged 6 months to 14 years was estimated at 58.6% [95% CI: 56.9 - 60.3] in Toumtouma, 75.9% [95% CI: 71.3 - 79.9] in Ourang, and 63.6% [95% CI: 58.2 - 68.7] in Arkoum.
CONCLUSIONS
In the three camps investigated, excess mortality was observed among households during the crisis phase (phase 2), with a significant difference in CMR due to deaths from violence among men. Among households living in Toumtouma camp, the CMR more than doubled and among households in Arkoum camp, it more than tripled. The population in Ourang camp seems to have been particularly affected by the violence, with CMR 20 times higher than in the pre- crisis period and mortality rates exceeding the standard emergency threshold (1 death/10,000 people/day). The vast majority of deaths occurred on the sites of origin or during displacement towards Chad (89% in Toutouma, 94% in Ourang and 79% in Arkoum). GAM and SAM prevalences among 6-59-month-olds were high in Ourang and Arkoum camps, with an alarming SAM prevalence of over 4%. In addition, the measles vaccination coverage, which ranged from 59% to 76% across the camps surveyed, was insufficient to prevent outbreaks.
Since April 15, 2023, fighting erupted in Sudan between the army led by General Abdel Fattah al-Burhan and the paramilitary Rapid Support Forces (RSF) under the command of General Mohamed Hamdan Dogolo, known as Hemeti. This war has caused a major humanitarian crisis in Sudan, with violent fighting spreading throughout the country, particularly in Darfur, and aggravating pre-existing inter-community tensions.
By the end of March, almost 30,000 civilians had fled to Chad in search of safety. By September 2023, according to data from the United Nations High Commissioner for Refugees (UNHCR), clashes between military and paramilitary forces had driven more than 420,000 people to flee to Chad in successive waves, of whom around 327,000 had settled in the Ouaddaï province. Chadian refugees and returnees live in very precarious conditions, with limited access to primary healthcare, water and food. Little recent data is available on the mortality, nutritional status, and vaccination coverage of refugee populations in camps in eastern Chad, particularly in Toumtouma, Ourang and Arkoum camps. The results of these surveys are essential for Médecins Sans Frontières (MSF) to better plan its humanitarian interventions, coordinate effectively with other actors, and communicate about the refugee crisis in eastern Chad.
METHODOLOGY
Three cross-sectional surveys were carried out, the first with systematic random sampling in Toumtouma camp from August 7 to 13, and the next two with cluster random geospatial sampling in Ourang camp from August 17 to 22 and Arkoum camp from August 30 to September 4, 2023. Each survey covered retrospective mortality, frequency and type of violent events experienced, nutritional status of children aged 6 to 59 months, and measles vaccination coverage among children aged 6 months to 14 years. The recall period ran from January 1 to the day of the survey, i.e., a minimum of 210, 228 and 241 days respectively. Two phases were considered: 1) the pre-crisis phase (Toumtouma: January 1 - March 14, 2023 / Ourang and Arkoum: January 1 - April 14, 2023) and 2) the crisis phase (Toumtouma: March 15 - day of survey / Ourang and Arkoum: April 15 - day of survey). In Toumtouma camp, the crisis phase started earlier due to inter-community tensions that erupted end of March in West Darfur and drove important population displacements towards Chad.
RESULTS
Retrospective mortality: In Toumtouma camp, of the 1,032 households included (i.e., 6,372 people), 59.7% were refugees, 35.9% returnees and 4.4% displaced persons. The crude mortality rate (CMR) was significantly higher in phase 2 (CMR: 0.58 deaths/10,000 people/day [95% CI: 0.43 - 0.74]) than in phase 1 (CMR: 0.20 deaths/10,000 people/day [95% CI: 0.07 - 0.33]). Eighty-nine percent of those who died were men. Violence (77%; n=48) was the main cause of death reported, followed by diarrhea (6%; n=4) and respiratory infection (5%; n=3). Among the deaths, 68% occurred in their town or village of origin, 21% during displacement and 11% in an unknown location. Most people who died came from El Geneina (40%), Tandulti (35%) and Umm Dam (16%) in Darfur.
In Ourang camp, of the 1032 households included (i.e., 6302 people), 99.0% were refugees and 1.0% returnees. The CMR was significantly higher in phase 2 (CMR: 2.25 deaths/10,000 people/day [95% CI: 1.77 - 2.74]) than in phase 1 (CMR: 0.11 deaths/10,000 people/day [95% CI: 0.02 - 0.20]). Eighty-three percent of those who died were men (3.88 deaths/10,000 people/day [95% CI: 3.01 - 4.76] in phase 2). Violence (82%; n=147) was the main cause of death reported, followed by measles (5%; n=9). Among the deaths, 69% occurred in their town or village of origin, 25% during displacement and 6% in Adre, Chad. Most people who died came from El Geneina (96%) in Darfur.
In Arkoum camp, of the 1029 households included (i.e., 5324 people), 98.4% were refugees, 1.3% displaced and 0.4% returnees. The CMR was significantly higher in phase 2 (CMR: 0.67 deaths/10,000 people/day [95% CI: 0.46 - 0.89]) than in phase 1 (CMR: 0.15 deaths/10,000 people/day [95% CI: 0.03 - 0.26]). Seventy-seven percent of those who died were men; the mortality rate among men was 1.14 [95% CI: 0.72 - 1.55] in the second phase. Violence (50%; n=28) was the main cause of death reported, followed by diarrhea (16%; n=9). Among the deaths, 52% occurred in their town or village of origin, 27% during displacement, 5% after their arrival in Chad and 16% in an unknown location. Most people who died came from Mistre (54%) and Kongu (29%) in Darfur.
Frequency and main causes of violence: Among households in Toumtouma, Ourang and Arkoum camps, the overall frequency of violence was 3.3%, 11.7% and 4.4% respectively. The main types of violence were beatings (71.0% in Toumtouma, 71.1% in Ourang, and 79.7% in Arkoum), and shootings (27.1% in Toumtouma, 34.7% in Ourang, and 15.1% in Arkoum).
Prevalence of acute malnutrition: Among children aged 6-59 months, the prevalence of global acute malnutrition (GAM) according to MUAC and/or bilateral oedema was 5.5% [95% CI: 4.1 - 7.5] in Toumtouma, 11.3% [95% CI: 9.2 - 13.8] in Ourang, and 11.6% [95% CI: 9.5 - 14.5] in Arkoum camp. Rates of severe acute malnutrition (SAM) were 2.3% [95% CI: 1.4 - 3.6] in Toumtouma, 4.8% [95% CI: 3.6 - 6.4] in Ourang, and 4.6% [95% CI: 3.4 - 6.3] in Arkoum.
Measles vaccination: Measles vaccination coverage among children aged 6 months to 14 years was estimated at 58.6% [95% CI: 56.9 - 60.3] in Toumtouma, 75.9% [95% CI: 71.3 - 79.9] in Ourang, and 63.6% [95% CI: 58.2 - 68.7] in Arkoum.
CONCLUSIONS
In the three camps investigated, excess mortality was observed among households during the crisis phase (phase 2), with a significant difference in CMR due to deaths from violence among men. Among households living in Toumtouma camp, the CMR more than doubled and among households in Arkoum camp, it more than tripled. The population in Ourang camp seems to have been particularly affected by the violence, with CMR 20 times higher than in the pre- crisis period and mortality rates exceeding the standard emergency threshold (1 death/10,000 people/day). The vast majority of deaths occurred on the sites of origin or during displacement towards Chad (89% in Toutouma, 94% in Ourang and 79% in Arkoum). GAM and SAM prevalences among 6-59-month-olds were high in Ourang and Arkoum camps, with an alarming SAM prevalence of over 4%. In addition, the measles vaccination coverage, which ranged from 59% to 76% across the camps surveyed, was insufficient to prevent outbreaks.
Journal Article > ResearchFull Text
Emerg Infect Dis. 2013 February 1; Volume 19 (Issue 2); DOI:10.3201/eid1902.120301
Minetti A, Kagoli M, Katsulukuta A, Huerga H, Featherstone A, et al.
Emerg Infect Dis. 2013 February 1; Volume 19 (Issue 2); DOI:10.3201/eid1902.120301
Despite high reported coverage for routine and supplementary immunization, in 2010 in Malawi, a large measles outbreak occurred that comprised 134,000 cases and 304 deaths. Although the highest attack rates were for young children (2.3%, 7.6%, and 4.5% for children <6, 6-8, and 9-11 months, respectively), persons >15 years of age were highly affected (1.0% and 0.4% for persons 15-19 and >19 years, respectively; 28% of all cases). A survey in 8 districts showed routine coverage of 95.0% for children 12-23 months; 57.9% for children 9-11 months; and 60.7% for children covered during the last supplementary immunization activities in 2008. Vaccine effectiveness was 83.9% for 1 dose and 90.5% for 2 doses. A continuous accumulation of susceptible persons during the past decade probably accounts for this outbreak. Countries en route to measles elimination, such as Malawi, should improve outbreak preparedness. Timeliness and the population chosen are crucial elements for reactive campaigns.
Journal Article > Meta-AnalysisFull Text
Vaccine. 2020 February 8; Volume 38 (Issue 11); DOI:10.1016/j.vaccine.2020.02.005
Juan-Giner A, Alsalhani A, Panunzi I, Lambert V, Van Herp M, et al.
Vaccine. 2020 February 8; Volume 38 (Issue 11); DOI:10.1016/j.vaccine.2020.02.005
Measles outbreaks occur periodically in remote and difficult to reach areas in countries such as the Democratic Republic of Congo. The possibility to keep measles vaccines at temperatures outside the cold chain for a limited period prior to administration would be an advantage for organizations such as Médecins Sans Frontières, which repeatedly respond to measles outbreaks in difficult contexts.
Using stability data at 37 °C and 40 °C provided by Serum Institute of India Private Limited we applied the product release model for Extended Controlled Temperature Conditions (ECTC) to evaluate the possibility of an out of the cold chain excursion.
Measles vaccine in the lyophilized form remains above the minimum required potency at the end of the shelf-life for up to 6 days at 37 °C or for 2 days at 40 °C.
This evaluation supports the use of a monodose presentation of measles vaccine in ECTC. This could be an advantage for outbreak response in isolated and difficult to reach areas. However the operational advantages of this approach need to be established.
Using stability data at 37 °C and 40 °C provided by Serum Institute of India Private Limited we applied the product release model for Extended Controlled Temperature Conditions (ECTC) to evaluate the possibility of an out of the cold chain excursion.
Measles vaccine in the lyophilized form remains above the minimum required potency at the end of the shelf-life for up to 6 days at 37 °C or for 2 days at 40 °C.
This evaluation supports the use of a monodose presentation of measles vaccine in ECTC. This could be an advantage for outbreak response in isolated and difficult to reach areas. However the operational advantages of this approach need to be established.
Journal Article > ResearchFull Text
Epidemiol Infect. 2011 October 5; Volume 140 (Issue 8); 1356-1365.; DOI:10.1017/S0950268811002032
Bharti N, Broutin H, Grais RF, Ferrari MJ, Djibo A, et al.
Epidemiol Infect. 2011 October 5; Volume 140 (Issue 8); 1356-1365.; DOI:10.1017/S0950268811002032
Throughout the African meningitis belt, meningococcal meningitis outbreaks occur only during the dry season. Measles in Niger exhibits similar seasonality, where increased population density during the dry season probably escalates measles transmission. Because meningococcal meningitis and measles are both directly transmitted, we propose that host aggregation also impacts the transmission of meningococcal meningitis. Although climate affects broad meningococcal meningitis seasonality, we focus on the less examined role of human density at a finer spatial scale. By analysing spatial patterns of suspected cases of meningococcal meningitis, we show fewer absences of suspected cases in districts along primary roads, similar to measles fadeouts in the same Nigerien metapopulation. We further show that, following periods during no suspected cases, districts with high reappearance rates of meningococcal meningitis also have high measles reintroduction rates. Despite many biological and epidemiological differences, similar seasonal and spatial patterns emerge from the dynamics of both diseases. This analysis enhances our understanding of spatial patterns and disease transmission and suggests hotspots for infection and potential target areas for meningococcal meningitis surveillance and intervention.
Journal Article > ResearchFull Text
Proc Biol Sci. 2010 September 22; Volume 277 (Issue 1695); DOI:10.1098/rspb.2010.0536
Ferrari MJ, Djibo A, Grais RF, Bharti N, Grenfell BT, et al.
Proc Biol Sci. 2010 September 22; Volume 277 (Issue 1695); DOI:10.1098/rspb.2010.0536
Seasonally driven cycles of incidence have been consistently observed for a range of directly transmitted pathogens. Though frequently observed, the mechanism of seasonality for directly transmitted human pathogens is rarely well understood. Despite significant annual variation in magnitude, measles outbreaks in Niger consistently begin in the dry season and decline at the onset of the seasonal rains. We estimate the seasonal fluctuation in measles transmission rates for the 38 districts and urban centres of Niger, from 11 years of weekly incidence reports. We show that transmission rates are consistently in anti-phase to the rainfall patterns across the country. The strength of the seasonal forcing of transmission is not correlated with the latitudinal rainfall gradient, as would be expected if transmission rates were determined purely by environmental conditions. Rather, seasonal forcing is correlated with the population size, with larger seasonal fluctuation in more populous, urban areas. This pattern is consistent with seasonal variation in human density and contact rates due to agricultural cycles. The stronger seasonality in large cities drives deep inter-epidemic troughs and results in frequent local extinction of measles, which contrasts starkly to the conventional observation that large cities, by virtue of their size, act as reservoirs of measles.
Journal Article > Short ReportFull Text
Science. 2011 December 9; Volume 334 (Issue 6061); DOI:10.1126/science.1210554
Bharti N, Tatem AJ, Ferrari MJ, Grais RF, Djibo A, et al.
Science. 2011 December 9; Volume 334 (Issue 6061); DOI:10.1126/science.1210554
Measles epidemics in West Africa cause a significant proportion of vaccine-preventable childhood mortality. Epidemics are strongly seasonal, but the drivers of these fluctuations are poorly understood, which limits the predictability of outbreaks and the dynamic response to immunization. We show that measles seasonality can be explained by spatiotemporal changes in population density, which we measure by quantifying anthropogenic light from satellite imagery. We find that measles transmission and population density are highly correlated for three cities in Niger. With dynamic epidemic models, we demonstrate that measures of population density are essential for predicting epidemic progression at the city level and improving intervention strategies. In addition to epidemiological applications, the ability to measure fine-scale changes in population density has implications for public health, crisis management, and economic development.