Dengue-Fieber

[Birgitt]

Manche der Waffen, die unsere Immunabwehr gegen eine Denguevirusinfektion in Stellung bringt, arbeiten auf lange Sicht eher dem Erreger zu, erkannte ein internationales Team von Virologen. Eine Sorte der körpereigenen Antikörper gegen das Virus, die eigentlich als Impfstoffe eingesetzt werden sollten, sorgt sogar dafür, dass Dengueviren ihre Zielzellen effizienter infizieren können. Dies könnte die ungeklärte Frage beantworten, warum einige Personen das Virus zuerst noch niederkämpfen können, dann aber bei einem späteren Zweitkontakt besonders anfällig sind ...

Impfstoffentwicklung: Mehr Schaden als Nutzen bei Dengueimpfung
06.05.2010 - spektrum

New clues into how the body fights off the tropical disease dengue fever could help in the search for a vaccine. The research, published in Science, also explains why those who recover from the virus have much worse symptoms if they catch it again ...

New clue to fighting dengue fever
06.05.2010 - BBC

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Birgitt

[Birgitt]

Alljährlich zittern die Länder Asiens vor einer neuen Dengueepidemie. Drei Forschungsprojekte stehen offenbar kurz davor, der heimtückischen Krankheit Herr zu werden ...

Kurz vor dem Durchbruch: Drei Forschungsprojekte gegen Dengue machen Hoffnung
27.07.2011 - spektrum

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Birgitt

[Birgitt]

Es gibt derzeit kein wirksames Medikament gegen das Dengue-Fieber, an dem jährlich bis zu 100 Millionen Menschen erkranken. Als Gegenmaßnahme bekämpfen Mediziner gerne den Überträger des Erregers auf den Menschen, die Gelbfiebermücke. In freier Wildbahn ist sie allerdings nicht auf Dauer auszurotten; daher soll die gefährliche Mückenpopulation ersetzt werden – mit Mücken, die das Virus nicht übertragen, dabei aber mindestens so leistungsfähig sind wie die Wildtyp-Mücken, die sie verdrängen sollen. Gelungen ist ein Austausch in freier Wildbahn aber noch nie. Jetzt wecken zwei Studien die Hoffnung, dass sich ein Erfolg doch erreichen lässt ...

Bakterien wappnen Mücken gegen Dengueviren
24.08.2011 - spektrum

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Birgitt

[Birgitt]

Das Denguefieber wird zuletzt immer häufiger als ernsthaft bedrohliche Krankheit der Zukunft wahrgenommen: Der in den Tropen durch Mücken übertragene Erreger verursacht zwar häufig nur grippeähnliche Symptome, kann aber auch innere Blutungen, hämorrhagisches Fieber oder einen fatalen Totalzusammenbruch des Immunsystems nach sich ziehen und zum Tode führen. Eine wirksame Behandlung oder vorbeugende Impfung ist nicht möglich. Schwer verläuft die Erkrankung allerdings vor allem nach einer Zweitinfektion – und dies offenbar in der Folge verschiedener Anpassungen des Immunsystems, die der Körper nach dem ersten Kontakt mit dem Virus einleitet. Einige neue Details dieser kontraproduktiven Immunreaktion hat nun ein Forscherteam um Eva Harris von der University of California in Berkeley herausgearbeitet ...

Halbwirksame Antikörper fördern gefährliche Fieberviren
22.12.2011 - spektrum.de

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Birgitt

[Birgitt]

Stechmücken mit fremden Genen sollen ganze Populationen ihrer Art vernichten und so eine der verheerendsten Krankheiten unserer Zeit eindämmen: das rasant um sich greifende Denguefieber. In Käfigen funktioniert die Strategie bereits. Dass aber vereinzelt schon transgene Moskitos ausgesetzt wurden, halten selbst viele Forscher für vorschnell ...

Moskitos mit Selbstmordgen
19.07.2012 - spektrum

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Birgitt

[Birgitt]

HEALTH: Dengue vaccine - still a long way off
11.09.2012 - IRIN

Dengue fever is classed by the World Health Organization (WHO) as a “major international public health concern”. WHO estimates that it infects 50-100 million people a year; it is a leading cause of death among children in Asia and Latin America, and it is now spreading outside its traditional heartlands to Africa and the Middle East.

But dengue is difficult to deal with. There is no cure, only treatment for the symptoms. And although there are effective vaccines against related viruses, like yellow fever and Japanese encephalitis, no one has yet succeeded in making a safe, effective vaccine against dengue.

Now a team of researchers working with the French drug company Sanofi Pasteur has carried out a randomized trial of a possible vaccine, involving more than 4,000 schoolchildren in northern Thailand, and have produced some interesting results. Their vaccine was only partly effective but the team’s findings - reported in the British medical journal, the Lancet - suggest that the development of a useful vaccine is getting closer.

Derek Wallace of Sanofi-Pasteur, one of the authors of the report, hailed their results as an important step. “Our study constitutes the first ever demonstration that a safe and effective dengue vaccine is possible,” he says. “Further trials [of the vaccine] are currently under way in a number of different countries, and we hope that the positive results of this trial will be confirmed by these larger studies.”

The trial took place in Thailand’s Muang District, based at Ratchaburi Regional Hospital, and involved researchers from Bangkok’s Mahidol University. Children aged 4-11 from 35 local schools were enrolled in the trials. Two-thirds of them were given three doses of the vaccine, known as CYD-TDV (a recombinant, live, attenuated tetravalent vaccine, based on yellow fever 17D vaccine strain, produced in Vero cells). The control group received either rabies vaccine or a placebo.

The children were vaccinated three times, at six-monthly intervals, and the researchers looked at the presence of dengue antibodies in their blood, as well as checking all cases of fever, mild or serious, and recording which were due to dengue.

The results were mixed. While the vaccine appears to be safe and well tolerated, it had only a limited effect. It gave useful protection against three strains of the disease, those known as DENV 1, 3 and 4. But although the vaccinated children produced antibodies to DENV 2, they still caught the disease just as often as the children in the control group. And unfortunately DENV 2 is the most common strain of dengue fever in northern Thailand.

Caveats

Scott Halstead of the International Vaccine Institute in Seoul, points out that even these results were made less useful by the fact that they did not test the vaccine on teenagers, who are more likely to get the severe form of the disease. He said: “Results from this vaccine trial provide hard evidence of protection against DENV 1, 3 and 4 mild disease but insufficient data to calculate vaccine efficacy rates for severe disease. Future dengue vaccine trials should provide robust evidence of efficacy against severe disease by selecting populations weighted to assure inclusion of sufficient numbers of at risk children.”

Bill Messer, clinical assistant professor at the Division of Infectious Diseases in the University of North Carolina School of Medicine, is blunter, pointing out that Sanofi Pasteur has been trying to refine the vaccine for the past decade (it started presenting papers on it in about 2001) but that the vaccine still cannot produce a "robust" response.

“This [study] is an encouraging first step, but far from where we need to be. It did not show the vaccine can prevent severe cases. That is an important endpoint [for a dengue vaccine]. You need to show recipient populations protection against severe dengue in order to encourage [vaccination],” he said.

While most dengue patients do not have symptoms or only mild pain and a rash, up to 10 percent develop a lethal “severe” form of the disease (previously known as dengue haemorrhagic fever). Only five children in the study had severe dengue, too few to analyse, a limitation the authors noted was being corrected in ongoing studies with 30,000 adults and children in dengue-endemic countries.

Messer also said the number of people tested thus far in Thailand is insufficient to prove the vaccine will not cause severe dengue. Health experts have expressed concern that complications from a dengue vaccine may result in infection rather than confer protection.

Despite some positive results from the trials, it seems that a dengue vaccine is still a long way off.

Quelle: IRIN

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Birgitt

[Birgitt]

Im Herbst brach das Dengue-Fiebers auf der portugiesischen Insel Madeira aus - es wandert nach Norden. Wissenschaftler haben nun die Ausbreitung der bisher unheilbaren Virus-Erkrankung und die Zahl der Neuinfektionen genauer betrachtet. Das Ergebnis: Das Risiko ist bisher von der Weltgesundheitsorganisation (WHO) als zu gering eingeschätzt worden. Denn weltweit sind dreimal mehr Menschen von Dengue-Fieber betroffen, als bislang angenommen: 390 Millionen Neuinfektionen gibt es pro Jahr, die WHO ging bislang von nur 50 bis 100 Millionen aus. Ein internationales Forscherteam unter Beteiligung der Uniklinik Heidelberg hat jetzt neben den neuen Daten auch eine Risiko-Karte der globalen Dengue-Verbreitung im Fachmagazin "Nature" veröffentlicht ...

Dengue-Risiko weltweit viermal höher als gedacht
11.04.2013 - scinexx / Uni Heidelberg

http://www.idams.eu/

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Birgitt

[Birgitt]

DENGUE/DHF UPDATE (86): ASIA
****************************
A ProMED-mail post
http://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org

*****

New dengue virus serotype 5
Date: Mon 21 Oct 2013
Source: Science Insider, American Association for the Advancement of Science (AAAS) [edited]
http://news.sciencemag.org/health/2013/ ... e-50-years


Scientists have discovered a new type of the virus that causes a centuries-old pestilence, dengue. The surprising find, announced at a major dengue conference [in Bangkok] today [21 Oct 2013], is bound to complicate efforts to develop a vaccine against a tropical disease that is becoming a more pervasive global menace. But it could shed light on where the pathogen came from and whether it is evolving into a greater threat. The finding "may change the way we think about dengue virus evolution and emergence," says Duane Gubler, a dengue expert at the Duke-NUS Graduate Medical School in Singapore.

There is no vaccine or drug against dengue, which is spread by mosquitoes and causes fever and sometimes excruciating joint pain and muscle aches. Patients typically recover on their own, though severe cases need medical support. Occasionally, the illness progresses to dengue hemorrhagic fever, a potentially fatal complication in which blood leaks through vessel walls. A dengue infection confers lifetime immunity to that particular type. But subsequent infection with a 2nd type increases the likelihood of serious illness. With that in mind, vaccine developers have strived to protect against all four types simultaneously.

That may have gotten more challenging. By chance, researchers screening dengue viral samples found a virus collected during an outbreak in Malaysia's Sarawak state in 2007 that they suspected was different from the four original serotypes. They sequenced the virus and found that it is phylogenetically distinct from the other 4 types. Experiments found that monkey antibodies produced against the new type differ significantly from those resulting from the previously known dengue viruses. "We discovered and characterized a new dengue serotype," announced Nikos Vasilakis, a virologist at University of Texas Medical Branch in Galveston, here today at the Third International Conference on Dengue and Dengue Haemorrhagic Fever.

"They've done a very good job in characterizing the virus, and it's convincing that it is distinct from the other four," says Thomas Scott, a dengue expert at the University of California, Davis.

What it may mean for controlling dengue is unclear. So far, dengue 5 has been linked to only one outbreak in humans. Vasilakis suspects that it is circulating, possibly among macaques, in the forests of Sarawak. If it spreads, it could make human vaccine development more challenging. "We don't need another complication in controlling dengue," Scott says.

Current efforts to rein in the disease are falling short. In talks here today [21 Oct 2013], researchers from Malaysia, the Philippines, and Thailand said that despite control programs launched in the 2000s, dengue cases are increasing, though the death toll is down thanks to better management of severe cases. "Dengue is spreading from urban to rural areas and to countries, such as Nepal, where it has not been seen before," said Samlee Plianbangchang, the World Health Organization Southeast Asia regional director. The annual global incidence, close to 390 million cases, is about 3 times the burden previously estimated, researchers reported in April in Nature.

Despite a recent setback in vaccine development, Plianbangchang said that projects in the pipeline have researchers "looking forward to a vaccine in the near future." But he adds that a vaccine will complement, not replace, efforts to contain dengue through mosquito control and public awareness. "Dengue will be with us for many years and could get worse," he said.

--
communicated by:
ProMED-mail
<promed@promedmail.org>

[Given the long-term, intensive dengue virus surveillance going on in Southeast Asia, it is surprising that a new dengue virus serotype, dengue virus 5, has been discovered only now. However, if the suggestion above that the virus has been maintained in non-human primates, perhaps the spillover into humans, with ongoing transmission, is a very rare event. Since the new serotype was isolated in 2007, with no subsequent reports since then, perhaps it is not being maintained in the human population currently. Intensified surveillance and virus typing of isolates collected over the past 6 years will provide an indication of its presence in time and space in Malaysia and Southeast Asia generally. - Mod.TY]

[Alexander]

Malaria, Dengue- und Chikungunya-Fieber werden zunehmend von Reisenden nach Europa eingeschleppt. Die Weltgesundheitsorganisation (WHO) warnt vor leichtsinnigen Umgang mit den exotischen Krankheiten. Exotische Krankheiten wie das Chikungunya-Fieber können sich durch unachtsame Reisende und wärmere Temperaturen auch in Europa breitmachen. Davor hat das Regionalbüro der Weltgesundheitsorganisation (WHO) am Mittwoch in Kopenhagen gewarnt. Das Chikungunya-Fieber tritt normalerweise in den Tropen auf und verursacht unter anderem Muskel- und Gelenkschmerzen ...

Merkur: WHO warnt vor Dengue-Fieber in Europa

Grüsse
Alexander

[Birgitt]

Von Mücken übertragen und ziemlich ansteckend: Gegen das Dengue-Fieber konnte man sich bislang nicht wirklich schützen. Jetzt gibt es in Deutschland die erste zugelassene Impfung dagegen – und womöglich bald sogar ein Gegenmittel ...

Erster Impfstoff gegen Dengue-Fieber auf dem deutschen Markt
17.03.2023 - BR

Weitere Informationen dazu siehe: CRM - Centrum für Reisemedizin und PEI - Paul-Ehrlich-Institut.

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Birgitt

[Birgitt]

Vor allem der amerikanische Kontinent registriert extrem hohe Zahlen von Dengue-Infektionen. Der Großteil davon entfällt auf Brasilien [...] Das Eindämmen sei wichtig, weil sich die Krankheit sonst auch in Ländern ausbreiten könne, in denen sie bislang kaum vorkommt ...

Hohe Zahl von Dengue-Fällen alarmiert WHO
31.05.2024 - spektrum

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Birgitt