26 February 2008

Where can we expect new epidemics?

Pyotr Smirnov, "Newspaper.Ru»

Scientists have identified the location of "hot spots" in which new infections should be expected, and identified "our lesser brothers" who have repeatedly turned out to be traitors over the past 64 years, throwing this or that infection to humanity. In the list of dangerous places on the planet, the United States and Japan are next to Africa and Southeast Asia.

If you believe the disappointing forecasts of infectious diseases and epidemiologists, then the world should literally freeze in anticipation of a new unknown threat. And if earlier most of the work was reduced, if not to intimidation, then to calculating potential losses and predicting "Doomsday", then a new study by British and American scientists predicts exactly where and from whom danger should be expected.

They tracked the stages of development of more than 335 infectious diseases from 1940 to 2004, assessing the role and contribution of various risk factors in the occurrence, spread and course of the disease. The work of scientists (Kate E. Jones et al., Global trends in emerging infectious diseases) is published in the latest issue of Nature.

Причиной более чем половины из 335 рассмотренных вспышек инфекционных заболеваний были бактерии, около четверти – вирусы, а дальше – простейшие, грибы и гельминтыOf the 335 outbreaks considered, more than half were caused by bacteria, about a quarter by viruses, and then by protozoa, fungi and helminths in descending order. Although the United States holds the first place in the number of detected infections, cases were often described there that actually originated in other parts of the world, and brought by tourists or migrants. The second reason for the leadership of the West is antibiotic–resistant infections that arise due to large-scale and not always skillful and correct prescribing of antibiotics.

According to the team of researchers, outbreaks of such "known" infections as antibiotic-resistant tuberculosis, chlorokine-resistant malaria and HIV are the result of a significant increase in population density, an increase in international trade, travel and changes in farming methods. It is these shifts in the way of everyday life of the vast majority of people since the 40s that have become the key reasons for the catastrophic increase in the number of new infections.

The 1980s especially distinguished themselves. About 100 new infections have appeared in ten years. HIV also played a significant role in this. Like 60% of the infections considered, the immunodeficiency virus refers to zoonoses – that is, transmitted from animals to humans.

According to the latest data, 72% of all zoonoses came from the wild, the remaining 28% were a gift from pets. Among the latter are the Nipah virus in Malaysia and the much more famous SARS of Chinese origin, which caused almost a complete stop of tourist trips to Southeast Asia.

The authors agree with the position of most epidemiologists that the most important thing is to stop the spread of the disease at an early stage, even when there is no specific method of its treatment. As the case of the notorious SARS has shown, the logic is simple and unique – the earlier the infection is caught, the less damage it has managed to cause. Isolation and banal methods of individual protection like masks and travel restrictions play a much greater role in preventing the spread of certain infectious diseases, especially on a global scale.

As the authors themselves emphasized, this approach to preventing the spread of new types of infections is fundamentally different from the control and research of existing diseases, although their proposed strategy is very similar to the traditional one – the British call for more thorough control of the "hot spots of infection" of our planet.

Kate Jones, one of the authors of the work, a senior researcher at the London Institute of Zoology, urges modern specialists in the field of viral and infectious diseases to think much bigger, since it will be much more difficult to hide from new diseases in the modern world than it was before, and the danger that has arisen in a small region may threaten the entire population of the globe..

By the way, SARS is an indicator of the possible inaccuracy of the initial data of this work. More recently, microbiologists have shown that humanity received the SARS virus from bats, and not from predators. However, such an amendment still does not affect the conclusions made by the Jones team, since the source is still wild animals, and the focus of the epidemic on the world map has not shifted.

But the most important thing is that the emergence of new infections unknown to mankind does not significantly differ from the transformation of existing ones into an antibiotic–resistant form.

Therefore, the list of "hot spots" based on 64 years of history, along with the already "proven" equatorial Africa and Southeast Asia, can include at first glance prosperous Australia, Europe and North America.

But the biggest threat comes from the developing countries of eastern Latin America, Asia and Africa. Jones and her colleagues suggest that a new threat should be expected from there.

Now there are particularly intensive population migrations and mixing of different ethnic groups in this region, contact with diverse and often wild animals remains part of normal life. In addition, the situation with the development of medicine remains difficult here, in particular, with the availability of medicines and especially antibiotics of various generations, as well as modern antiviral drugs.

Число возникновения инфекций в разных регионах мира с 1940 по 2004 год
The number of infections in different regions from 1940 to 2004.
One circle corresponds to an outbreak of infection in a one–degree area, and the size of the circle corresponds to the number of cases.

Scientists emphasize that a more accurate localization on the map of the "hot spots" themselves requires much more calculations, for which the authors of the work plan to compare their data with climatic and demographic models in the near future. So they pay attention to the global environmental change, which is already causing the emergence of new directions of animal migration, and consequently, their prokaryotic and non-cellular satellites.

Portal "Eternal youth" www.vechnayamolodost.ru26.02.2008

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