Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

West Africa: meningitis epidemics driven by the wind

05.04.2005


A meningitis epidemic hits West Africa every year, affecting 25 000 to 200 000 people. It has long been known that the timing of this epidemic and its spatial distribution within the “Meningitis Belt”, situated between 10° and 15° North, are closely linked to climatic conditions. Involved in the AMMA programme ( 1 ), IRD and University of Paris-VII researchers ( 2) produced the first quantified description of this relationship using statistical methods. They linked up the annual changes in atmospheric humidity and wind speed to epidemiological data collected over several years in this region. The number of cases of meningitis thus appears in synchrony with seasonal climate variations, epidemic onset coinciding with the time when the winter winds are strongest. These results should be useful for the development of epidemiological early-warning systems in this region, in order to prevent epidemics and try and limit their effect.



The Sahelo-Sudanian band of Africa is an endemic area for meningococcal meningitis (MCM). The disease, an infection of the meninges by the bacteria Neisseria meningitidis, is highly contagious and affects 25 000 to 200 000 people per year, particularly children. Outbreaks occur every year between February and May. Their geographical distribution is contained within what is called the Meningitis Belt circumscribed between 10° and 15° of latitude North. Several factors contribute to epidemic onset, in particular loss of immunity among communities in the face of the bacterial agent, owing to the renewal of generations and the increase in the number of individuals who have never been in contact with it, and also because of climatic conditions. Sahelo-Sudanian Africa is under a climate of alternating dry season in winter and a monsoon season in summer. This alternation is linked to the shift in latitude of the Intertropical Front which corresponds to the convergence zone between the northern winds, called the Harmattan, and the monsoon winds coming from the South. In winter, Sahelo-Sudanian Africa receives the influence of the Harmattan winds. These warm, dry winds, are dust-loaded and cause damage to the mucous membranes of the respiratory system. Conditions are propitious for the transmission of the MCM bacteria to the blood and hence for triggering meningitis epidemics.

Through their involvement in the AMMA programme (1), researchers from the IRD and partner institutes (2) have just for the first time quantified this link between the epidemics cycle and climate variations. Statistical methods brought out evidence of a coincidence between the seasonal variability of the number of cases of meningitis recorded in Mali and the climate dynamics on the scale of this zone.


The Harmattan winds are the dominant feature of the winter climate of Sahelo-Sudanian Africa. The research team therefore sought to assess the influence of these winds on the epidemics. In order to do this, they used wind speed and atmospheric humidity data to develop synthetic atmospheric indices essential for building models of annual climate cycles. These indices were then correlated with epidemiological datasets coming from WHO (World Health Organization) weekly reports on Mali, between 1994 and 2002.

For each of these nine years, a winter maximum for the Harmattan was established. This represents the week when the wind index was highest. On average, this maximum corresponds to the sixth week of the year, between 7 and 15 February, when the Intertropical Front is situated at its southern latitude. Statistical analysis shows that changes in the wind speed index in the course of these seasons are concomitant with the rise in the number of people infected with meningitis, the start of the epidemic coinciding with the Harmattan winter maximum. The end of the epidemics is usually signalled by a recession in the sixteenth week, with the onset of the rainy season, which removes the conditions favourable for meningococcus transmission. The same analysis was then conducted on the atmospheric humidity index. It reinforced the message of these results, the lowest atmospheric humidity and the epidemic onset also corresponded to the sixth week of the year, 7 to 15 February.

Thanks to this preliminary research, combining climate science and health sciences, it is possible to think in terms of setting up epidemiological monitoring systems in order to have early warning of meningitis epidemics in this region of West Africa and attempt to limit their impact. However, these results do not provide a way of defining a possible link between the intensity of winter and the size of the epidemic. Moreover, the climate model used is founded on a period of only nine years, and possibly large variations of climate or epidemics over a larger time-scale cannot be taken into account. This model will consequently have to be tested over longer periods and on a finer spatial scale, in order to study these variations in more detail and assess their impact on the progression of the disease within Mali.

The setting-up of an Environmental Research Observatory (ORE AMMA-Catch), devoted to collecting measurements of climatic and health parameters in West Africa, should contribute to extending and continuing this research in a public health perspective.

Marie Guillaume – DIC

Translation : Nichlas Flay

1. Several IRD research units (UR 086 LODYC/LOCEAN, UMR 7617 IRD-CNRS-UPMC and UR 165 UMR 2724 IRD-CNRS ) have worked with the University of Paris VII (UFR GHSS).

2. The AMMA programme ( Analyse multidisciplinaire de la mousson africaine) was launched at the start of 2002 on the initiative of the IRD, the CNES, the CNRS, Météo-France and the African organizations ACMAD (African Center for Meteorological Applications to Development) and AGRHYMET (Centre d’Agro-hydro-meteorologie of Niamey, Niger).

Helene Deval | EurekAlert!
Further information:
http://www.ird.fr

More articles from Health and Medicine:

nachricht NTU scientists build new ultrasound device using 3-D printing technology
07.12.2016 | Nanyang Technological University

nachricht How to turn white fat brown
07.12.2016 | University of Pennsylvania School of Medicine

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>