Eventual role of asymptomatic cases of dengue for the introduction and spread of dengue viruses in non-endemic regions.

In dengue virus infections the asymptomatic cases are much more frequent than the symptomatic ones, but their true role in the introduction and subsequent spread of dengue viruses in non-endemic regions remains to de clarified. We analyzed data from English and French literatures to assess if viremia in asymptomatic dengue infections might be sufficient to represent a true risk. During outbreaks of dengue a large number of individuals are infected and since viremia levels in symptomatic patients are known to vary by many orders of magnitude, it is reasonable to augur that a proportion of asymptomatic cases might reach levels of viremia sufficient to infect competent mosquitoes. In addition, a number of new ways of contamination in man by dengue viruses were recently described such as blood transfusion, bone marrow transplantation, and nosocomial infections that may be worth considering.

Characterization of a novel wood mouse virus related to murid herpesvirus 4.

Two novel gammaherpesviruses were isolated, one from a field vole (Microtus agrestis) and the other from wood mice (Apodemus sylvaticus). The genome of the latter, designated wood mouse herpesvirus (WMHV), was completely sequenced. WMHV had the same genome structure and predicted gene content as murid herpesvirus 4 (MuHV4; murine gammaherpesvirus 68). Overall nucleotide sequence identity between WMHV and MuHV4 was 85 % and most of the 10 kb region at the left end of the unique region was particularly highly conserved, especially the viral tRNA-like sequences and the coding regions of genes M1 and M4. The partial sequence (71 913 bp) of another gammaherpesvirus, Brest herpesvirus (BRHV), which was isolated ostensibly from a white-toothed shrew (Crocidura russula), was also determined. The BRHV sequence was 99.2 % identical to the corresponding portion of the WMHV genome. Thus, WMHV and BRHV appeared to be strains of a new virus species. Biological characterization of WMHV indicated that it grew with similar kinetics to MuHV4 in cell culture. The pathogenesis of WMHV in wood mice was also extremely similar to that of MuHV4, except for the absence of inducible bronchus-associated lymphoid tissue at day 14 post-infection and a higher load of latently infected cells at 21 days post-infection.

[Lessons from the Greek dengue epidemic of 1927-1928]. / En 1927-1928, la dengue s'abattait sur la Grèce: les enseignements d'une epidémie.

Epidemics of dengue have occurred in Greece in 1881, 1889, 1895-1897 and 1910, but the outbreak which has affected this country in 1927-1928 has been of a peculiar severity and geographic extension. More than one million inhabitants were sick and about 1500 died. The outbreak extended to the whole Greek territory and evolved in two epidemics waves. The first one occurred during the second half of 1927, was not very extensive and relatively benign. The second wave, explosive, started on July 1928, reached its summit in August and then declined until November. During this second part of the outbreak severe clinical events were identified, such as hemorrhagic, neurological or renal disorders, along with infections during pregnancy. The mosquito Aedes aegypti was the alone vector of the disease and dengue type 1 virus was the main etiological agent both in 1927 and 1928. The eventual activity of the dengue type 2 virus and its possible role in the pathogenesis of severe clinical forms of dengue, during 1928, remains unclear. Relatively speaking, it is possible to parallel this "historical" outbreak with the recent epidemic episode which appeared in 2007 in the Ravenne's area in northern Italy. This outbreak was caused by the Chikungunya virus after its importation from southern India by an infected traveller. There were 249 autochthonous registered cases but no severity nor death was observed. The local vector was Aedes albopictus, an invasive mosquito of Asian origin which has progressively invaded a number of European countries including France. Thus, Europe is now at risk to the emergence of outbreaks caused by "exotic" viruses imported by travellers returning from other parts of the world.

[Sixty years ago, cell cultures finally permitted the poliomyelitis virus to multiply easily]. / Il y a 60 ans (1949), les cultures cellulaires permettaient enfin de multiplier aisément les virus de la poliomyélite.

In 1949, three American virologists, John F. Enders, Thomas H. Weller and Frederick C. Robbins, from the Harvard Medical Scholl and working at the Children's Medical Centre, Boston, Mass., have provoked a true revolution in Virology. Here, they have succeeded in readily multiplying the three poliomyelitis viruses in vitro, in non-nervous cells cultures. A few years afterwards (1954), they were collectively honoured by the Nobel Prize of Physiology and Medicine. This discovery not only has quickly led to the production of efficient poliomyelitis vaccines (J. E. Salk, 1953; A. B. Sabin, 1955) but also has permitted to easily isolate a number of already known viruses (measles, rubella, mumps, herpes simplex and herpes zoster) or until then totally unknown viruses (adenovirus, echovirus, cytomegalovirus). These progresses have significantly contributed to improve diagnosis, sanitary surveillance and vaccinal prophylaxis of human and animal viral diseases. Moreover, the cells cultures techniques have also benefited to other domains of fundamental Biology, such as cellular biology, genetics, cancerology, biology of the reproduction and regenerative medicine as well.

[The centenary of the discovery of the vibrio El Tor (1905) or dubious beginnings of the seventh pandemic of cholera]. / Le centenaire de la découverte du vibrion d'El Tor (1905) ou les débuts incertains de la septième pandémie du choléra.

As a direct result of the 1865 cholera epidemic, health authorities have realized that the Mecca pilgrimage represented a permanent risk for the global diffusion of this scourge. It was decided to open five quarantine stations along the Red Sea, among them the El Tor station. There, Felix Gotschlich, in 1905, isolated for the first time the El Tor vibrio from pilgrims deceased when coming back from Mecca. This vibrio had atypical biologic properties. Although agglutinated by specific antisera, it was haemolytic for human and animal red cells, a character not shared by the true Vibrio cholerae. Moreover there was no cholera epidemic at this time both in Mecca or at El Tor station, and the pilgrims have deceased from illnesses other than cholera. Was this vibrio actually pathogen? This question was the origin of never-ending discussions among bacteriologists and it was concluded that this micro-organism was only a "laboratory curious". In fact, from 1937 to 1958, four epidemics of so-called "paracholera" or "enteritis choleriformis", with very high death rates, occurred in the south of Celebes (Sulawesi) Islands and the responsible was the El Tor vibrio. However according to the alleged non-pathogenic character of this bacteria, local authorities omitted to declare infected this area. Awakening was quite rude! By 1961, again from Celebes Islands ,the El Tor vibrio emerged as true pathogen responsible for the 7th pandemic, invading about 100 countries around the world. It has killed hundreds of thousands of patients since 1961. Then it turned evident that the El Tor vibrio was in fact a peculiar biotype of Vibrio cholerae O1. By 1992, new epidemics appeared in India and Bangladesh due to a new biotype, Vibrio cholerae O 139 Bengal, antigenically distinct from but genetically related to the El Tor vibrio.

[Global threats from emerging viral diseases]. / Les virus bougent: périls planétaires.

Emerging viral diseases are nothing new. Smallpox probably reached Europe from Asia in the 5th century, and yellow fever emerged in the Americas during the 16th century as a consequence of the African slave trade. Dengue fever arose simultaneously in South-East Asia, Africa, and North America during the 18th century. In 1918-1919 the so-called Spanish flu spread like wildfire through all five continents, killing between 25 and 40 million people. The second half of the 20th century saw the emergence of HIV/AIDS (1981), among other viral diseases. Even more worrying is the fact that emerging and re-emerging viral diseases have had a tendency to spread more quickly and more widely during the last decade, invading whole countries and continents; witness the recent outbreaks of Nipah virus, West Nile, Rift Valley fever, SARS, monkeypox, avian flu (H5N1) and Chikungunya. The complex factors underlying these new trends are briefly discussed.

[Modern Egypt and the history of microbiology. The campaign of Bonaparte]. / Egypte moderne et histoire de la microbiologie: De i'expédition de Bonaparte à nos jours.

The history of microbiology and parasitology in Egypt started with Bonaparte's campaign and the contemporary clinical reports from the physicians of the "Armee d'Orient" (1798-1903). Later, basic discoveries in parasitology and bacteriology have been the facts of German scientists such as Theodor Bilharz, Robert Koch and Arthur Looss. At the beginning of the First World War German physicians were evicted from Cairo and British parasitologists took over as Robert Leiper succeeded in clarifying the life cycle of schistosomiasis. Virology studies on poliomyelitis in Egypt started in 1942-1943 but British virologists were quickly supplanted by the Americans as the U.S. NAMRU-3 laboratory opened in Cairo in the 50s. Many basic contributions to the epidemiology of the viral diseases in the Nile valley have been established during the past forty years, concerning enteroviruses, mosquito and tick-borne arboviruses as well as hepatitis C virus.

[Chikungunya virus: its recent spread to the southern Indian Ocean and Reunion Island (2005-2006)]. / Le virus chikungunya: son extension récente dans le sud de l'Océan Indien et à l'lle de la Réunion (2005-2006).

Chikungunya virus (alphavirus, Togaviridae) is transmitted by mosquitoes of the Aedes genus and responsible for a dengue-like acute disease characterized by severe arthralgias sometimes persisting during months and eventually years. Its geographical distribution is large, including west, central, east and southern tropical Africa, India and South-eastern Asia. Since 2005 february, Chikungunya disease invaded a number of islands in southern Indian Ocean, namely Comoro, Mauritius, Seychelles and Reunion islands. In this French department, it was responsible for 110000 to 200000 infections, neurological disorders, many deaths and some congenital infections not previously observed during preceding epidemics.

[When the Egyptian mummies are speaking about the infections that have made them ill]. / Quand les momies égyptiennes nous parlent des infections qui les tourmentaient.

The microbiological study of mummies has started in 1910 when Sir M.A. Ruffer first applied the histologic methods to the study of mummified tissues and found Schistosoma haematobium ovas dated from the XXth dynasty. Up to the 1990 years, morphological methods including radiology, computed tomography, endoscopy, history, electron microscopy, and serology have been the main tools used in Paleopathology. They led to identify schistosomiasis, dracunculiasis, trichinosis, ascariasis and bone tuberculosis as the most prevalent diseases of the ancient residents of Egypt. The recent introduction of molecular methods (PCR) allowed t confirm the high prevalence of helminth diseases and tuberculosis among these populations, but also added new data exemplified by the widespread distribution of Plasmodium falciparum malaria. In addition, cases of bacterial septicemias and diphteria possibily occurred. Thousands of human and animal mummies remain to be studied with the hope to discover another pathogens responsible for viral or zoonotic infections prevalent during the pharaons' times.

[Impact of global climate changes on arboviruses transmitted to humans by mosquitoes and ticks]. / Incidence des changements climatiques planétaires sur les arboviroses transmises à l'homme par des moustiques et des tiques.

Global warming [+0.5-0.6 degree C during the second half of the 20th century] seems a reality although climatologists did not reach a common agreement on its actual origin, and this phenomenon may still increase along the 21st century [+1.5 to 6 degrees C]. Epidemiologists are anxious at the eventual effects of the resulting climate change on the evolution of arbovirus infections transmitted to human beings by hematophagous vectors such as mosquitoes and ticks. Analysis of the literature devoted to this problem did not lead to precise conclusions and the mathematical models used seems insufficient for they take into account mainly the climatic factors and not enough the human ones. Examples of dengue, european tick-borne encephalitis and other arbovirus infections are discussed. Peculiar attention is devoted to the eventual effects of climatic changes on the hibernation process in some small mammals and the timing of bird's migrations, involved in enzootic cycles of arboviruses. It is likely that arbovirus diseases may locally extend, both in latitude and altitude, leading to outbreaks, but regressions may also occur.

Viral evolution and emerging viral infections: what future for the viruses? A theoretical evaluation based on informational spaces and quasispecies.

Emergence of new viruses is dependent on the intrinsic and extrinsic constraints exerting on viral evolution. Intrinsic constraints are semantic and grammatical in nature. They are analysed here in reference to Hamming's spaces, driving to a new interpretation of the evolution of the quasispecies of Manfred Eigen. Extrinsic constraints are relevant to the fact that viral evolution is always a co-evolution story, with two or three partners implicated (the viruses, their hosts and eventually their vectors). They imply that viral phylogenies are disconnected, and viruses constitute a polyphyletic system. A possible consequence is that potential viral families are already known, or at least are present in nature, in such a manner that the frames for future viral evolution are already determined and that the probability for the emergence of a new frame is nil. Nevertheless, the emergence of new pathogens in the existing frames remain possible.

Histoire des virus: de la variole au SIDA

Aborda a questão da origem da febre amarela, as pesquisas medicas desenvolvidas sobre a doenca e a atuacao do medico cubano Carlos Finlay na descoberta de seu modo de transmissao.(MAM)