Médecine


Duration of malaria transmission in sub-Saharan Africa (source, WHO)

Before you read the last word of this short essay, about 20 children under five will die from malaria somewhere on our planet.

Malaria strikes 500 million people a year and kills nearly 3 millions of people; mostly in sub-Saharan Africa. Caused by blood parasites – Plasmodium – transmitted to humans by the bite of infected female mosquitoes – Anopheles, the disease hits more than 100 countries, with 2.4 billion persons at risk – the third of the world’s population.

The bad news is that children carry the largest burden in endemic area; more than 1 million of them will not celebrate their fifth birthday. Yet, this number might seem not alarming by itself. But if you recall the 200 thousand deaths from the recent Asian tsunami, you can easily do the math and figure out that every year, in Africa, five tsunamis hit innocent children. Sadly, I have to say that the fight malaria against malaria receive, nevertheless, did not receive at least the same level of attention and support over the years, as did one tsunami.

Malaria is not a disease of developed countries, rather, it hits the poorest of the poor; not surprisingly, we can argue that the lack of potential market in developed countries for potent drug or vaccine against malaria has played against it for many years. This point was vividly highlighted during Bill Gates statement at the 2005 World Health Assembly, when he said to the rich countries, “let’s be frank, if these epidemics were raging in the developed world, people with resources would see the suffering and insist that we stop it” (2005, World Health Assembly).

If human being is born free and equal in both dignity and rights as stated in the Universal Declaration of Human Right, our common sense of humanity and decency should be called upon to use our science and our heart to save the lives of those innocent children. Today, more than ever, every death from malaria is a needless death. This disease is treatable and effective means for control and prevention are available. Nevertheless, the gap in bringing these solutions to those in need remains huge. Financial resources, policies and capacities to deliver them fall far short of what is required. These issues are common for malaria and other global health challenges as HIV/AIDS and tuberculosis. All constitute a major bottleneck for the development of the African continent, preventing the poorest of the poor from holding a rung onto the ladder of development.

Without being too cynical, we should keep in mind that two centuries ago, smallpox vaccine was discovered, and a century later the poliomyelitis vaccine became a reality. Our generation has no option for failure in the fight against malaria in this century. The greatest hope comes from the field of research with the sequencing of the genome of the parasite, the mosquito vector, and the host human. The renewed commitment of the recent decade from governments, donors, and scientific community will, we hope, definitively bring malaria into the museum./_

Landry Tsague.

Le virus aviaire, qui vient de faire une réapparition en Angleterre a été tranmis de l’oiseau à l’homme: la barrière des espèces séparant homme et animal a donc été franchie. Mais jusqu’ici aucune transmission d’homme à homme n’a été observée. Comment pourrait-elle se produire? Une première possibilité est celle qui semble à l’origine de la terrible “grippe espagnole” de 1918. Le virus aviaire, après s’être introduit chez l’homme, subit alors une modofication sur quelques bases de son ARN (mutation) qui lui permet de s’adapter à l’homme, puis de se transmettre d’homme à homme. Il est “humanisé”.

Une deuxième possibilité nécessite un intermédiaire animal que la biologie rapproche à la fois de l’oiseau et de l’homme: le cochon. Proche de l’oiseau, il peut assez facilement recevoir le virus aviaire. Celui-ci, rencontrant chez le porc un autre virus animal, peut échanger avec lui quelques fragments de génome (c’est le réassortiment, modification plus importante que la mutation). Proche de l’homm, le cochon pourra lui transmettre le virus ainsi formé avec transmission ultérieure d’homme à homme. Ce mécanisme semble avoir été celui des grippes asiatiques de 1957 et 1958. D’où l’intérêt de surveiller l’apparition possible d’une maladie suspecte dans les élevages de porcs en région d’épidémie aviaire.

Dans une troisième possibilité, l’homme se comporte comme le cochon, un virus aviaire ayant pénétré chez lui (plus difficilement que chez le porc) peut y rencontrer un virus de l’hommeet, grâce à un réassortiment (moins probable chez l’homme), il peut produire un virus “humanisé” susceptible de passer à d’autres hommes. Cette modification pourrait être possible avec le virus de la grippe humaine. D’où l’intérêt de la vaccination contre la grippe humaine pour que l’homme ne puisse se comporter comme un cochon. Le virus “humanisé”, quel que soit son mode d’apparition, entraînerait une épidémie humaine.

Serge NZIETCHUENG avec l’autorisation du professeur Edmond Bertarnd