Emerging diseases: resistance is organized

Alerts are increasing in recent years. Infectious diseases are causing more and more regular epidemics, but researchers are on the warpath and are brewing their weapons.

The twentieth century was the fight against viruses and bacteria, with the discovery of antibiotics and vaccination. The scientists thought they were done with them ... But Ebola, Zika and all their friends proved us wrong. Barely detected, infectious diseases are back in force, one new per year, and one alert every five years. Today, these diseases are described as "emerging". "It may be a completely new virus, like AIDS or SARS," says Professor Eric Caumes, a specialist in infectious and tropical diseases, but known pathogens also fall into this category when they undergo mutations, such as the antibiotic-resistant influenza or Koch bacillus (TB). "
In the family, we meet other old acquaintances. Those who appear in an unexpected corner of the globe (the chikungunya for example), or those who are back when they were thought to be controlled (yellow fever). But scientists are watching over ...

We have the names of the culprits!On the dock, we find bacterium, parasite or fungus, although it is most often a virus. "Hosted by a wild animal, it passes into humans by crossing the" species barrier ", that is to say, through genetic mutations that allow it to proliferate outside their favorite host," says the Professor Arnaud Fontanet, Director of the Epidemiology Unit for Emerging Diseases at the Institut Pasteur. AIDS and Ebola are transmitted to us by the big primates, SARS by the civet, and his cousin, the Mers-Cov, seems to have arrived by the dromedaries. Another responsible: the Aedes mosquito (including the famous tiger mosquito). Specimens are increasingly numerous on the surface of the globe and are the main vector of zika, chikungunya, dengue fever or yellow fever. Knowing this, scientists are monitoring particular species. For the flu, for example, they keep a close eye on poultry. As the virus is very unstable, it can mutate in the blink of an eye and go from the chicken to the man.
Men are also responsible for the extent of epidemics since the second half of the twentieth century. Deforestation brings wild animals closer, the proliferation of cities and air transport encourage the spread of viruses. Not to mention the gigantic increase in the world population, from 1.7 billion in the early twentieth century to 7 billion today. We have little taken on these elements. The only answer is medical: cure diseases, but first detect them as soon as possible.

Diagnosis: faster and more mobile
To pinpoint the beginning of the epidemic is to prevent its spread. Different levels of standby overlap. For example, at the international level, the World Health Organization oversees a network of laboratories. In France, Public Health France coordinates 70 surveillance systems and examines the evolution of a whole series of pathogens. "But researchers are mostly connected to each other around the world," said Professor Caumes. Specialists also have computer tools for decision support, such as algorithms to determine, for example, whether new cases of Legionnaires' disease present an epidemic risk or not.
When caregivers report suspicious symptoms, scientists can now rely on sophisticated devices to quickly identify the pathogenic strain. Biological tests include, in particular, DNA chips that directly detect the genetic sequences of viruses, or high throughput sequencing techniques. "These advances are important, but the challenge is mainly to develop mobile laboratories, able to move in difficult areas, take samples and make quick diagnoses," says Arnaud Fontanet.

Soon vaccines and drugs?Research focuses in particular on antivirals. The 2000s saw the appearance of treatments capable of preventing the proliferation of influenza in the body, like the famous Tamiflu. But by 2007, some influenza strains were already able to resist him. Other antivirals are under development, some of which may be available within five or six years. Researchers are also bombarding coronaviruses, such as SARS and Mers-Cov. The goal: to develop broad-spectrum antivirus that can fight against a virus that we do not know yet.
Several vaccine candidates are already advanced, especially against chikungunya, zika and dengue, although the results have disappointed the hopes for the latter pathology. In the fight against Ebola, a vaccine for primates has recently been developed and another for humans would be close to commercialization. "That of a Canadian team was tested during the 2014-2015 epidemic," explains Professor Arnaud Fontanet, "he has passed the various phases of the test and there are strong arguments to say that he protects effectively." Unfortunately, the development of vaccines sometimes suffers from the ephemeral nature of the disease. The finished epidemic may not happen again for years, public opinion moves on, and often funding dries up ...

Anticipate the epidemics of tomorrow
Some tracks seem more promising, even if the surprise remains always the rule in the occurrence of these health crises. Researchers fear a new influenza virus, as aggressive as bird flu, but highly contagious. Bacteria are also in the viewfinder. "Antibiotic resistance is a very serious emerging problem," says Dr. Caumes, "Some bacteria no longer respond to any known antibiotic, and research is poor in this area." In addition to the example of tuberculosis, the specialist cites Escherichia coli, these intestinal bacteria particularly responsible for urinary tract infections.
Scientists do not sit idly by waiting for the next disaster. They are working on processes to accelerate research when the time comes. A few months ago, the international alliance Coalition for Epidemic Preparedness Innovations (CEPI) came into being with the aim of developing vaccines for 11 pathogens responsible for epidemics. "This would advance the development to the point where it will remain only the test phase of the efficacy in humans, which will be performed during a reappearance of the disease," says Arnaud Fontanet. CEPI also undertakes public-private partnerships to obtain the necessary credits. The effect "Ebola" has poured donations: it's time to use them.

To read: "Emerging Diseases", Jean-Philippe Braly, Ed Quae.

Read also 10 reflexes to fight against a virus

Video: Changes in Clinical Diagnostics and Tracking Infectious Diseases (December 2019).

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