Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


West Africa: meningitis epidemics driven by the wind


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:

More articles from Health and Medicine:

nachricht Advanced analysis of brain structure shape may track progression to Alzheimer's disease
26.10.2016 | Massachusetts General Hospital

nachricht Indian roadside refuse fires produce toxic rainbow
26.10.2016 | Duke University

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: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

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

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

3-D-printed magnets

26.10.2016 | Power and Electrical Engineering

Advanced analysis of brain structure shape may track progression to Alzheimer's disease

26.10.2016 | Health and Medicine

3-D-printed structures shrink when heated

26.10.2016 | Materials Sciences

More VideoLinks >>>