Tag Archives: dengue

Pandemic restrictions could be linked to 750,000 fewer dengue cases

Almost three-quarters of a million fewer cases of dengue were registered in 2020, which researchers suspect is linked to COVID-19restrictions on people’s movements and interactions, according to a new study. For the researchers, targeting places such as schools could greatly reduce dengue transmission hot spots and play a key role in stopping the spread of the disease.

Image credit: Flickr / Vaccines at Sanofi

Dengue is a big cause of acute morbidity in over 120 countries worldwide, with sustained increases year on year. Countries in Southeast Asia and the Americas regions are the worst affected, with over two million cases reported there in 2020 — but as the planet continues to heat up, more and more areas become vulnerable to dengue.

The virus isn’t transmitted human to human but by the Aedes aegypti species of mosquitoes which needs hot temperatures. Hot and humid tropical climates are ideal for transmission, and cases generally peak between June and September. Symptoms typically include a high fever, headache, vomiting, muscle and joint pains, and a characteristic skin rash. Overall, dengue infects some 400 million people a year, killing 40,000.

For dengue, the COVID-19 pandemic was a unique opportunity to better understand how different environments and human mobility contribute to transmission. That’s why an international group of researchers decided to carry out the first multi-continent study of the effects of public health and social measures on dengue incidence.

“Before this study, we didn’t know whether COVID-19 disruption could increase or decrease the global burden of dengue,” Oliver Brady, study co-author, said in a statement. “While we could assume reduction in the human movement would reduce the virus transmission, it would also disrupt the mosquito control measures already in place.”

Dengue and Covid-19

Brady and a group of researchers from Beijing Normal University and the London School of Hygiene & Tropical Medicine (LSHTM) looked at monthly dengue cases between 2014 and 2020, using data from the World Health Organization (WHO). They covered 23 countries, 16 in Latin America and seven in Southeast Asia, as well as climate data such as temperature.

The researchers then looked at two measures of Covid-19 related disruption – public health and social measures (school and public transport closure and stay-at-home requirements) and human behavior through time spent at public and residential locations. They also incorporated the strength of the restrictions in lockdowns in different countries.

By combining this data, they showed that reduced time spent outdoors was linked with reduced dengue risk. Nine out of 11 countries in the Philippines, the Caribbean, and Central America had a full suppression of their dengue season in 2020, while other countries had a much-reduced season. Countries that set their pandemic restriction measures at the peak of the dengue season had a sharper decline of dengue cases.

The decrease in cases could also be linked to a lower rate of people seeking treatment for dengue, reduced availability of laboratory testing, and a higher potential of misdiagnosis, the researchers said. However, some countries like Sri Lanka predicted this could be a problem early in the pandemic and took measures, encouraging people to get diagnosed and seek treatment. Overall, this suggests that COVID-19 lockdowns also led to drops in dengue.

“Dengue control efforts are focused on or around the households of people who get sick. We now know that, in some countries, we should also be focusing measures on the locations they recently visited to reduce dengue transmission. For all the harm it has caused, this pandemic has given us an opportunity to inform new interventions and targeting strategies to prevent dengue,” Brady said.

In the long term, more routine measurement of the prevalence for dengue as well as a better understanding of how treatment-seeking behavior changes at different phases of dengue and COVID-19 epidemics will be important, the researchers wrote. That will require continued monitoring of the dengue trends in 2021 and beyond, including the collection of human mobility data.

The study was published in the journal The Lancet.

Scientists cut dengue fever cases by 77% using bacteria-infected mosquitoes

The target for elimination: Aedes albopictus. Image credits: Centers for Disease Control and Prevention’s Public Health Image Library.

Researchers affiliated with the World Mosquito Program, a non-profit concerned with protecting communities across the world from mosquito-borne diseases, just reported that its most recent trial meant to cull dengue in Indonesia was a stunning success. After releasing treated mosquitoes that were infected with a bacteria that makes them sterile, over the course of three years the number of dengue cases plummeted by nearly 77% while the number of dengue hospitalizations dropped by 86%.

The Wolbachia method

Dengue is a brutal mosquito-borne disease that causes flu-like symptoms but can be lethal and kill up to 20% of those with severe dengue. In the last five decades, dengue has gone from being present in a handful of countries to being endemic in 128 countries, where about four billion people live. In this timeframe, the number of dengue cases has increased 30-fold. As a result, the World Health Organization (WHO) listed dengue as one of the top global health threats in 2019 alongside Ebola, global flu pandemic, HIV, antimicrobial resistance and many others.

There is no specific treatment for dengue fever. For severe dengue, medical care by physicians and nurses experienced with the effects and progression of the disease can save lives – decreasing mortality rates from more than 20% to less than 1%. Maintenance of the patient’s body fluid volume is particularly critical to severe dengue care.

Dengue is transmitted by Aedes aegypti mosquitoes, which are responsible for a number of other illnesses including Zika and chikungunya. It is difficult to control or eliminate Ae. aegypti mosquitoes because they are highly resilient and can rapidly bounce back to initial numbers after disturbances such as droughts or human interventions. Their eggs can withstand desiccation (drying) and survive without water for several months on the inner walls of containers. But they may have finally met their match — the Wolbachia method.

Only female mosquitoes bite humans, which means that only females can transmit viruses. When mosquitoes are infected with the Wolbachia bacterium — a microbe present in at least 60% of all insects but rarely found in mosquitoes — two things happen. For starters, it makes most male mosquitoes sterile. Secondly, the bacteria are transmitted to offspring only by females.

Once a mosquito is infected with the bacterium, it makes it harder for viruses such as dengue to reproduce inside the insects, making the transmission from person to person far less likely. Because the effect of Wolbachia infection on insect reproduction favors the survival of Wolbachia-infected females over uninfected females, Wolbachia can rapidly spread through an insect population.

Wolbachia is harmless to humans. The benefits are that this is a non-chemical approach and that other insects and mosquitoes are not harmed.

Manipulating mosquitoes to stop spreading dengue with some help from bacteria

In 2017, researchers with the World Mosquito Program partnered with the Tahija Foundation and Gadjah Mada University and released Wolbachia mosquitoes within a 26km2 area of Yogyakarta City, Indonesia. The site was subdivided into 24 clusters, 12 of which were randomly selected to house Wolbachia mosquitoes, while the other dozen clusters were left untreated to act as a control.

Now, the team has reported the results of the trial in the New England Journal of Medicine, showing that Wolbachia deployments reduced dengue incidence by 77% and dengue hospitalisations by 86%.

Over the course of the trial, 318 dengue cases were detected in the untreated areas and only 67 in the Wolbachia-treated areas. There were only 13 hospitalizations for dengue in the Wolbachia-treated area compared to 102 in the untreated area. 

According to the researchers, once Wolbachia is established, it remains at a very high level in the mosquito population. The release of the Wolbachia mosquitoes was done transparently with the support of the local population.

Households voluntarily hosted these mosquito release containers, to which Wolbachia-carrying mosquito eggs, water and fish food were added once every two weeks, for 4-6 months. Adult Wolbachia-carrying mosquitoes emerged from the containers, then bred with wild-type Ae. aegypti mosquitoes until almost all Ae. aegypti in the intervention areas carried Wolbachia.

“In Yogyakarta, everybody knows somebody who has been impacted by dengue. Dengue is present in all provinces of Indonesia and is endemic in many large cities and small towns. The results of the RCT is welcome news for the people of Yogyakarta and a major breakthrough for the World Mosquito Program’s ambition to protect the wider Indonesian population,” reads a statement by the World Mosquito Program.

These results are consistent with those from other trials performed in Australia and Brazil, giving confidence that the reduction in dengue incidence can be replicated using the Wolbachia method in other parts of the globe. However, this needs to be thoroughly tested since differences in the circulating dengue serotypes can influence the results of the intervention.

Here’s how Skrillex’s music could help fight Zika and dengue fever

Despite advances in technologies, diseases transmitted by Aedes aegypti mosquitoes, including Zika, chikungunya, and dengue—are still serious public health problems worldwide. It is difficult to control or eliminate Ae. aegypti mosquitoes because they are highly resilient and can rapidly bounce back to initial numbers after disturbances such as droughts or human interventions. Their eggs can withstand desiccation (drying) and they can survive without water for several months on the inner walls of containers.

As with most mosquito-borne diseases, efforts to fight Aedes-borne viral illnesses have mainly focused on the application of insecticides. Although insecticides have been historically useful in managing mosquito-borne diseases, increased resistance to all four classes of insecticide used to date and adverse effects on the health of animals and humans have led to anti-pesticide activism.

A recent scientific study may have added a new tool in the fight against diseases carried by Aedes aegypti mosquitoes – electronic music by Skrillex, specifically dubstep.

Sound is “crucial for reproduction, survival, and population maintenance of many animals,” says a team of international experts from Universiti Malaysia Sarawak (Malaysia), Mosquito Research and Control Unit (Cayman Islands), Fukuoka University (Japan), Lambung Mangkurat University (Indonesia), Universiti Sains Malaysia, Universiti Malaysia Terengganu, and Mahidol University (Thailand).

Adults Aedes aegypti mosquitoes were presented with two sound environments (music-off or music-on). Discrepancies in visitation, blood feeding, and copulation patterns were compared between environments with and without music. Scary Monsters and Nice Sprites, a track by Skrillex was chosen because of its mix of very high and very low frequencies.

“In insects, low-frequency vibrations facilitate sexual interactions, whereas noise disrupts the perception of signals from conspecifics [members of the same species] and hosts,” the scientists said. Female adult mosquitoes were “entertained” by the track and attacked hosts later and less often than those in a dubstep-free environment. Scientists said, “the occurrence of blood feeding activity was lower when music was being played”. The scientists also found that mosquitoes exposed to the song had sex “far less often” than mosquitoes without music.

The results, which were published in the journal Acta Tropica, were good news for the global health community and for Skrillex. This observation that such kinds of music can delay host attack, reduce blood feeding, and disrupt mating offers new avenues for the development of music-based personal protective and control measures against Aedes-borne diseases.

The album Scary Monsters and Nice Sprites won two Grammys at the 54th Annual Grammy Awards, one for Best Dance Recording, and another for Best Dance / Electronica Album. Since Skrillex has teamed up with Ty Dolla $ign on Mariah Carey’s ‘The Distance’, perhaps a combination of beats from Scary Monsters and Nice Sprites plus Mariah’s whistle notes would even be more effective and make the Aedis mosquitoes proceed with Caution.

Dengue vaccine candidate looks promising in Phase 3 Trial

Yellow fever is spread by mosquitos. Image credits: James Gathany.

Dengue is a mosquito-borne disease that causes flu-like symptoms but can be lethal and kill up to 20% of those with severe dengue. In the last five decades, dengue has spread from being present in a handful of countries to being endemic in 128 countries, where about four billion people live. WHO has listed dengue as one of the top global health threats in 2019 alongside Ebola, global flu pandemic, HIV, antimicrobial resistance and many others.

Dengue cases have also increased 30-fold in this time period. In addition, more people are traveling than ever before and millions of travelers to endemic areas are also at risk of being bitten by the disease-carrying mosquitoes. A high number of cases occur in the rainy seasons of countries such as Bangladesh and India. Now, its season in these countries is lengthening significantly (in 2018, Bangladesh saw the highest number of deaths in almost two decades), and the disease is spreading to less tropical and more temperate countries such as Nepal, that have not traditionally seen the disease. An estimated 40% of the world is at risk of dengue fever, and there are around 390 million infections a year.

There is no specific treatment for dengue fever. For severe dengue, medical care by physicians and nurses experienced with the effects and progression of the disease can save lives – decreasing mortality rates from more than 20% to less than 1%. Maintenance of the patient’s body fluid volume is critical to severe dengue care.

(FILES) This file photo taken on April 4, 2016 shows a nurse showing vials of the anti-dengue vaccine Dengvaxia, developed by French medical giant Sanofi, during a vaccination program at an elementary school in suburban Manila.

The first dengue vaccine, Dengvaxia® (CYD-TDV) developed by Sanofi Pasteur was licensed in December 2015 and has now been approved by regulatory authorities in 20 countries for use in endemic areas in persons ranging from 9-45 years of age. In April 2016, WHO issued a conditional recommendation on the use of the vaccine for areas in which dengue is highly endemic as defined by seroprevalence of 70% or higher. In November 2017, the results of an additional analysis to retrospectively determine serostatus at the time of vaccination were released. The analysis showed that the subset of trial participants who were inferred to be seronegative at time of first vaccination had a higher risk of more severe dengue and hospitalizations from dengue compared to unvaccinated participants.

A new vaccine, TAK-003, is based on a live-attenuated dengue serotype 2 virus. Preliminary data through 15 months (Part 1 of the trial) showed that the vaccine met the primary efficacy endpoint of preventing virologically-confirmed dengue fever induced by any of the four dengue serotypes. In addition, the vaccine was found to be well-tolerated with no significant safety concerns.

“We are excited to publish the data in a peer-reviewed journal as quickly as possible,” said Rajeev Venkayya, MD, and President at Takeda. Part 2 of the trial will evaluate secondary outcome measures including vaccine efficacy by serotype, baseline serostatus and severity; long-term safety and efficacy evaluation (an additional 3 years) will be included in the third part of the study.

Takeda expects to file for licensure once Part 2 of the study is complete in each of the eight countries where its clinical trial took place: Brazil, Colombia, Panama, Dominican Republic, Nicaragua, Philippines, Thailand and Sri Lanka. The company plans to file in the U.S. and Europe within a year of filing in dengue-endemic countries, Venkayya said. Takeda and dengue experts are already planning ways to review the latest vaccine data with those regulators.

The Global Dengue & Aedes-Transmitted Diseases Consortium (GDAC), a group funded in part by drugmakers that works closely with WHO, scheduled a meeting for early March in Bangkok with regulators from at least six countries to take a first look at Takeda’s results, said Dr. In-Kyu Yoon, director of GDAC.

Dengue vaccine approved for use in Mexico, Brazil and Philippines

Scientific American recently reported that the three countries most affected by dengue fever have approved the use of the first vaccine against this affliction. Officials from Mexico, Philippines and Brazil hope that this will curb the nearly 400 million new infections each year, 22,000 of which result in death.

Dengue symptoms include fever (sometimes as high as 105°F/40°C), pain in muscles, bones and joints, headaches, nose and gum bleeds and other similarly pleasant manifestation. The disease is caused by a virus which spreads through mosquito-bites and is closely related to the Zika virus. It emerged as a worldwide problem in the 1950s and up to now, apart from trying to keep the insects at bay, there was not much people could do to avoid infection.

The countries and areas at risk of dengue transmission are shaded in orange, and the geographical extension of dengue is indicated in red. Data are from the World Health Organization, 2007.
Image via nature

Although dengue rarely occurs in the continental United States, it is endemic in many parts of the world. Clocking in at a staggering 400 million new infections per year, an efficient vaccine for dengue could make a huge difference in the livelihood of those living in high-risk areas.

Enter Sanofi. While it’s not 100 percent effective against dengue infection, trials show that it reduces the chances of contracting the virus from infected mosquitoes by 60 percent (in patients over the age of 9.)

But, more importantly, the drug is 95.5 percent effective in treating dengue hemorrhagic fever, a deadly form of the disease that affects an estimated 500,000 people each year. Sanofi has the potential to drastically reduce incidents of DHF, saving countless lives.

Experts project the first Sanofi inoculations in Brazil, the Philippines and Mexico will take place this year, after each country completes negotiations with Sanofi’s parent company. The World Health Organization will examine the vaccine in April before making global recommendations.

Two children have a gene mutation which protects them from many viruses, including influenza, hepatitis C and HIV

MOGS gene, via Wikipedia.

A new study on which a swarm of scientists worked on showed that two children (an 11 year old boy and a 6 year old girl)  have a mutation which greatly reduces viral replication in HIV, dengue fever, herpes simplex virus type 2 infection, and hepatitis C – effectively protecting them from the viruses.

The two children are siblings, and their parents are healthy, apparently normal from every point of view. The two children feature a mutation in the gene encoding MOGS – a glycoprotein believed to be important in the process of myelinization of nerves in the central nervous system (CNS).

The thing is, this mutation comes with even more downsides – these two kids have a serious list of problems such as a complex disorder characterized by dysmorphic facial features, generalized hypotonia, seizures, global developmental delay, cerebral atrophy, a small corpus callosum, optic-nerve atrophy, sensorineural hearing loss, hypoplastic genitalia, chronic constipation, and recurrent bone fractures, as well as hypogammaglobulinemia – a type of primary immune deficiency disease characterized by a reduction in all types of gamma globulins. Basically, the disadvantages greatly outweight the advantages.

Researchers write in the paper:

“In summary, the two siblings we describe have a paradoxical clinical phenotype of severe hypogammaglobulinemia and increased resistance to particular viral infections. We evaluated the patients’ immune systems and susceptibility to viral diseases and found an association with a rare MOGS N-glycosylation defect.”

They only reported the findings, not going into additional discussions about the potential benefits of this kind of study. However, it seems pretty clear that finding a way to eliminate all the negative side effects while maintaining the viral resistance could have massive implications – though that’s pretty far away. A drug working on the same mechanism called miglustat was developed in the ’90’s for HIV treatment, but the side effects were still significant.

Scientific Reference.