Virus World

Discover how Aedes aegypti mosquito eggs harboring ZIKV and CHIKV pose a new public health challenge, urging a revamp in control strategies. A groundbreaking discovery by scientists at the Federal University of Goiás (UFG) has unveiled that Aedes aegypti mosquito eggs can carry the ZIKV and CHIKV viruses, responsible for Zika and chikungunya respectively. This finding, highlighting a vertical transmission route, underscores a significant public health concern and calls for enhanced surveillance and control measures.

Unveiling the Mechanism of Vertical Transmission

The study, published in the source , marks a paradigm shift in understanding how these viruses are spread. Traditionally, transmission was thought to occur horizontally, with mosquitoes becoming vectors after biting an infected host. However, the detection of ZIKV and CHIKV in mosquito eggs before they hatch means mosquitoes can be born already infected, ready to spread the virus without prior contact with an infected host.

Implications for Public Health and Surveillance

Diego Michel Fernandes da Silva, the study's coordinator and a doctoral student at UFG, emphasized the significance of this discovery for public health. With mosquitoes capable of being born as carriers of these viruses, the potential for rapid spread increases, especially in urban environments. This adaptation mechanism allows for easier dispersal and poses a considerable challenge for controlling outbreaks of Zika and chikungunya. The study's findings necessitate a reconsideration of current prevention strategies, urging health authorities to intensify local epidemiological surveillance and explore innovative ways to eliminate the mosquito population.

Research Methodology and Findings

The research team captured Aedes aegypti eggs and adult mosquitoes across three major regions of Goiânia, Goiás, from January to September 2022. After isolating the heads and thoraxes of 1,570 adult females for analysis, the eggs were raised in laboratory conditions until they hatched. Among these, two groups tested positive for CHIKV and one for ZIKV, confirming that vertical transmission had occurred and that these mosquitoes could transmit the viruses upon reaching maturity. This revelation has profound implications for the fight against diseases like Zika and chikungunya. By demonstrating that viruses can be transmitted vertically from mosquitoes to their offspring, the study not only expands our understanding of these diseases' epidemiology but also underscores the urgent need for innovative control measures. As we grapple with the potential for increased transmission, this research serves as a critical call to action for health authorities worldwide to reassess and fortify their disease prevention strategies.

Cites Study Published in Revista da Sociedade Brasileira de Medicina Tropical (2024):

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10890825/ 

Two human cases of West Nile virus have been reported in New York as the virus has been detected in a record number of mosquitoes in the city, health officials said Tuesday.  Across the city's five boroughs, 1,068 mosquito pools have tested positive for the virus, according to the New York City Department of Health and Mental Hygiene. The city recorded 779 positive pools at the same time last year. The two human cases were reported in Brooklyn and Queens, the health department said in a statement. The West Nile virus is most commonly spread to people through the bite of an infected mosquito, according to the US Centers for Diseases Control and Prevention. Those cases happen during mosquito season, which starts in the summer and continues through fall, the CDC said.  "We are in the height of West Nile virus season, but there are things you can do to decrease your risk of being bitten," New York City Health Commissioner Dr. Ashwin Vasan said. Using an insect repellent and wearing long sleeves and pants, especially when outside during late and early hours, may help prevent the risk of getting bit, Vasan explained. 

There is no vaccine for the virus, so preventative measures are the most effective way to avoid infection. Symptoms of West Nile infection include fatigue, fever, headache, body aches and rash. However, 80% of infected people do not display any symptoms, according to the CDC. In rare cases, the virus can also be spread through blood transfusions, organ transplants, exposure in a lab setting or from mother to infant. Less than 1% of infected people develop a serious neuroinvasive illness, such as encephalitis (inflammation of the brain) or meningitis (inflammation of the protective membranes covering the brain and spinal cord), according to the CDC. As of August 9, a total of 54 human cases of the virus disease have been reported to the CDC this year. Last year, 2,695 human cases were reported to the agency.

CNN's Aya Elamroussi contributed to this report.

Scientists have detected Zika virus RNA in free-ranging African bats. RNA, or ribonucleic acid, is a molecule that plays a central role in the function of genes. A team of Colorado State University scientists, led by veterinary postdoctoral fellow Dr. Anna Fagre, has detected Zika virus RNA in free-ranging African bats. RNA, or ribonucleic acid, is a molecule that plays a central role in the function of genes.  According to Fagre, the new research is a first-ever in science. It also marks the first time scientists have published a study on the detection of Zika virus RNA in any free-ranging bat. The findings have ecological implications and raise questions about how bats are exposed to Zika virus in nature. The study was recently published in Scientific Reports, a journal published by Nature Research. Fagre, a researcher at CSU's Center for Vector-Borne Infectious Diseases, said while other studies have shown that bats are susceptible to Zika virus in controlled experimental settings, detection of nucleic acid in bats in the wild indicates that they are naturally infected or exposed through the bite of infected mosquitoes. "This provides more information about the ecology of flaviviruses and suggests that there is still a lot left to learn surrounding the host range of flaviviruses, like Zika virus," she said. Flaviviruses include viruses such as West Nile and dengue and cause several diseases in humans. CSU Assistant Professor Rebekah Kading, senior author of the study, said she, Fagre and the research team aimed to learn more about potential reservoirs of Zika virus through the project.

The team used 198 samples from bats gathered in the Zika Forest and surrounding areas in Uganda and confirmed Zika virus in four bats representing three species. Samples used in the study date back to 2009 from different parts of Uganda, years prior to the large outbreaks of Zika virus in 2015 to 2017 in North and South Americas. "We knew that flaviviruses were circulating in bats, and we had serological evidence for that," said Kading. "We wondered: Were bats exposed to the virus or could they have some involvement in transmission of Zika virus?" The virus detected by the team in the bats was most closely related to the Asian lineage Zika virus, the strain that caused the epidemic in the Americas following outbreaks in Micronesia and French Polynesia. The first detection of the Asian lineage Zika virus in Africa was in late 2016 in Angola and Cape Verde. "Our positive samples, which are most closely related to the Asian lineage Zika virus, came from bats sampled from 2009 to 2013," said Fagre. "This could mean that the Asian lineage strain of the virus has been present on the African continent longer than we originally thought, or it could mean that there was a fair amount of viral evolution and genomic changes that occurred in African lineage Zika virus that we were not previously aware of."

Fagre said the relatively low prevalence of Zika virus in the bat samples indicates that bats may be incidental hosts of Zika virus infection, rather than amplifying hosts or reservoir hosts. "Given that these results are from a single cross-sectional study, it would be risky and premature to draw any conclusions about the ecology and epidemiology of this pathogen, based on our study," she said. "Studies like this only tell one part of the story." The research team also created a unique assay for the study, focusing on a specific molecular component that flaviviruses possess called subgenomic flavivirus RNA, sfRNA. Most scientists that search for evidence of Zika virus infection in humans or animals use PCR, polymerase chain reaction, to identify bits of genomic RNA, the nucleic acid that results in the production of protein, said Fagre.

Kading said her team will continue their research to try and learn more about how long these RNA fragments persist in tissues, which will allow them to approximate when these bats were infected with Zika virus. "There is always a concern about zoonotic viruses," she said. "The potential for another outbreak is there and it could go quiet for a while. We know that in the Zika forest, where the virus was first found, the virus is in non-human primates. There are still some questions with that as well. I don't think Zika virus has gone away forever."

See Scientific Reports (April 26, 2021):

https://doi.org/10.1038/s41598-021-87816-5 

Mosquitoes zapped with radiation to make them sterile are set to be released into the wild in a bid to fight outbreaks of dengue fever.  The World Health Organization has announced that from next year it will start large-scale studies of what is known as the sterile insect technique. This involves irradiating male Aedes mosquitoes, the species responsible for the spread of diseases such as dengue, Zika and chikungunya. The scientists hope that the sterile males will be released in such large numbers that they will overwhelm the native male population and then go on to mate with females. But they will produce no offspring so the insect population will reduce over time, alongside the number of cases of the disease. The technique has been used for about 50 years in the management of agricultural pests, such as the Mediterranean fruit fly, and experts are confident that it poses no risk to either human health or the environment. 

WHO has been working with organisations including the International Atomic Energy Agency (IAEA) and the Food and Agriculture Organisation on preliminary studies in countries including Bangladesh, Cuba, Brazil and Mauritius. Dengue fever has become a major health threat with 110 countries around the world suffering outbreaks this year. WHO believes that as many as five million cases may be reported by the end of 2019 - up from an average of three million in previous years. Urbanisation and climate change are expected to see the mosquito responsible for transmitting the disease spread to new areas.  Raman Velayudhan, coordinator of WHO’s department of neglected tropical diseases, said there was a desperate need for new tools to control the Aedes mosquito which lives in urban areas, bites during the day and whose eggs are able to survive for long periods. 

“It’s a unique mosquito which has silently expanded and today is present in over 130 countries,” he told a press conference, where the trial was announced. Experts insist the technique is safe - the mosquitoes are not “radioactive” and there is no genetic mutation. WHO also stresses that the technique will not harm the wider eco-system. There are more than 3,500 different types of mosquito that serve as food for animals so removing one species will have little impact. The IAEA is looking at refining the technique for malaria-carrying mosquitoes, although Dr Velayudhan said there were already control tools for this mosquito, such as bed nets and indoor residual spraying. 

The MCPDH announced that they will offer free, at-home blood testing for residents after a person tested positive for dengue. The Maricopa County Department of Public Health announced on Monday that they have identified a person who recently tested positive for the mosquito-borne viral disease known as dengue. According to the MCDPH, the person who tested positive might have been exposed by an infected mosquito in Maricopa County. "Routine mosquito surveillance performed by Maricopa County Environmental Services Department (MCESD) has detected the dengue virus in a mosquito trap in one neighborhood in the county," the MCDPH said in a news release. According to Mayo Clinic, dengue is common in tropical and subtropical areas of the world with millions of cases reported each year. It is rare in the United States, however, with an average of less than 20,000 cases per year. The World Health Organization notes that while some cases are asymptomatic, symptoms from dengue fever can range from severe flu-like symptoms to severe bleeding, organ impairment, plasma leakage and death. The MCDPH has not revealed who was infected or the severity of their infection, however.

As a result of the positive test, the department announced that Public Health teams will be visiting neighborhood residents to offer free, at-home blood testing if they are interested. Those teams will also include representatives offering information for preventing bites and mosquito breeding around their homes, the MCDPH said. MCDPH did not specify which neighborhood the department would be testing in. “While previous dengue cases in Maricopa County have been related to travel to countries where dengue commonly occurs, it is important to understand if others could have been exposed or if this is an isolated incident.” said Dr. Nick Staab, MCDPH medical epidemiologist. “This is in addition to our routine investigations of anyone suspected to have dengue or other mosquito-borne diseases.” The MCDPH said that Maricopa County will field teams of staff and volunteers to conduct the free testing for residents five years and older and provide mosquito prevention kits as well. The tests will identify if any person has been infected in the last several months even if the person is asymptomatic, the MCDPH said.

“This simple test can provide information that is valuable to our residents and, on a neighborhood level, to Public Health,” Staab said. “When we look at results of this testing and mosquito testing across the county, we can determine if there is any risk to others and what Public Health, Environmental Services, and other partners can do to prevent illness.” The department said that they will send postcards to homes in the specific neighborhood to their door, to notify them about their upcoming visit before field teams go door-to-door over the next week to offer the testing, prevention kits and information on how the test results will be shared with those tested or their legal guardians.

Scientists sent mice on scented chases and swabbed the armpits of people infected with dengue to pinpoint an odor that attracts mosquitoes. Being bit by a mosquito carrying dengue or Zika virus can make you sick. The infection can also make you even more attractive for other mosquitoes, new research finds. It’s an itchy concern for anyone infected, but also poses a major risk to communities at large: Mosquitoes that aren’t already carrying the viruses could be more drawn to sick humans, become infected, and go on to infect more humans. The spread of dengue, in particular, is a threat, with about half the world’s population at risk and hundreds of millions of cases each year. Most cases are asymptomatic, but serious cases can lead to fever and vomiting, and in some instances, organ failure or death. The study, published Thursday in Cell, identifies a specific scent emitted from both Zika- and dengue-infected mice that makes them more attractive to mosquitos than those without the viruses. It also points to a potential route to neutralize the olfactory flag. “This is a highly, highly influential study,” said Nikolaos Vasilakis, a professor of pathology at the University of Texas Medical Branch in Galveston who was not involved with the research. “I’m pretty sure it’s going to foster or spin off several new lines of experimentation to get a better understanding of what’s happening in humans.” In the experiments, performed at Tsinghua University in Beijing, mosquitos in a cage could enter a chamber with virus-infected mice or one with healthy mice. The mosquitos had no preference among the mice when the experimental group was newly infected, but on days four and six of infection, around 70% of the mosquitos flew to the infected group.  “An essential scientific question is how mosquitoes effectively orient to viremic hosts with a high frequency,” lead author Gong Cheng wrote in an email. Body temperature, carbon dioxide levels, and scent are all known factors in attracting mosquitos to a host. The researchers isolated each factor in repeated experiments to systematically eliminate temperature and carbon dioxide and identify scent as the attractant.

To determine exactly what caused the change in scent, they analyzed hundreds of potential volatile compounds emitted from the sick mice and narrowed it down to one, called acetophenone. The amount of acetophenone on the infected mice was found to be 10 times higher than on the uninfected ones. “Regarding virus-induced changes in behavior, this study is like a unicorn because of how in-depth they were able to go on all these levels,” said Megan Wise de Valdez, an associate professor of biology at Texas A&M in San Antonio, who was also not involved. She said the study’s methodology was so rigorous she plans to teach it in the classroom. Still, when it comes to results, “a mouse is a mouse is a mouse is a mouse,” said Vasilakis — meaning the stronger insights come from looking at humans. So the researchers took it a step further.  They applied acetophenone to human hands and found it had a similar effect in attracting mosquitos. And after finding that dengue patients were putting out higher levels of acetophenone than healthy people, they collected odors from the armpits of both and applied the scent extracts to filter paper. The perfumed papers were stuck to a human volunteer’s hand in the trapping chambers. Those with the odors of dengue patients attracted more mosquitos. After pinpointing the cause of the increased attraction, the researchers tested a possible solution. They’d found that when viruses like Zika or dengue invade the body, they suppress a particular antimicrobial protein on the skin that controls acetophenone. Researchers were able to reactivate that protein and stop the overproduction of acetophenone by feeding the mice isotretinoin, a vitamin A derivative often used as acne medication. After that, mosquitos fed on the treated mice less than the untreated mice. “If that holds in longitudinal studies, then there is hope that this is going to be an extremely effective tool in the arsenal that we have against infectious diseases,” said Vasilakis. The researchers will focus their next studies on both the host — by testing potential treatments to suppress acetophenone in human dengue patients — and the vector, by searching for the genetic key in mosquitos that identifies and seeks the acetophenone, and attempting to remove it. In the global effort to fight the viruses, this research lays new groundwork. But it will likely take years to decades before we have a solution as simple as a pill for patients to ward off hungry mosquitos.

Research Published in Cell (June 30, 2022):

https://www.sciencedirect.com/science/article/abs/pii/S0092867422006419 

A combination of the Zika virus and Chikungunya, two mosquito-borne infections, increase stroke risk, a new study reports. University of Liverpool researchers and Brazilian collaborators have been investigating the link between neurological disease and infection with the viruses Zika and chikungunya. These viruses, which mostly circulate in the tropics, cause large outbreaks of rash and fever in places like Brazil and India. Zika is widely known to cause brain damage in babies following infection in pregnancy, but the new research shows it can also cause nervous system disease in adults. The study of 201 adults with new onset neurological disease, treated in Brazil during the 2015Zika and 2016 chikungunya epidemics, is the largest of its kind to describe the neurological features of infection for several arboviruses circulating at the same time. The new research shows that each virus can cause a range of neurological problems. Zika was especially likely to cause Guillain-Barre syndrome, in which the nerves in the arms and legs are damaged. Chikungunya was more likely to cause inflammation and swelling in the brain (encephalitis) and spinal cord (myelitis). However, stroke, which could be caused by either virus alone, was more likely to occur in patients infected with the two viruses together.

Stroke occurs when one of the arteries supplying blood to the brain becomes blocked. The risk of stroke is known to be increased after some types of viral infection, like varicella zoster virus, which causes chickenpox and shingles, and HIV. Stroke is also being recognised increasingly as a complication of COVID-19. This has important implications for the investigation and management of patients with viral infection, as well as for understanding the mechanisms of disease. In total 1410 patients were screened and 201 recruited over a two-year period at Hospital da Restauração in Recife, Brazil. Comprehensive PCR and antibody testing for viruses was carried out in Fiocruz laboratories. Of the 201 patients admitted with suspected neurological disease linked to Zika, chikungunya or both, 148 had confirmation of infection on laboratory testing, around a third of whom had infection with more than one virus. The median age of patients was 48, and just over half the patients were female. Only around 10% patients had fully recovered at discharge, with many having ongoing issues like weakness, seizures, and problems in brain function. Of the stroke patients, who were aged 67 on average, around two thirds had infection with more than one virus.

Many of the people who had a stroke had other stroke risk factors, such as high blood pressure, indicating that stroke following Zika and chikungunya viral infection may most often be seen in those who are already high risk. Dr Maria Lúcia Brito Ferreira, neurologist and head of department at Hospital da Restauração, leading the Brazilian team said: “Zika infection most often causes a syndrome of rash and fever without many long-term consequences, but these neurological complications — although rare — can require intensive care support in hospital, often result in disability, and may cause death.” ..

Original Study Published in The Lancet Neurology (October 2020):

https://doi.org/10.1016/S1474-4422(20)30232-5

West Nile Virus Spreads In Los Angeles - Los Angeles, CA - More mosquitoes in the region tested positive for the potentially deadly virus, and authorities are asking residents to take precautions. The hot weather is just egging the mosquito season on, and officials Friday announced the spread of the West Nile Virus in the San Fernando Valley. 

According to the Greater Los Angeles County Vector Control District, 11 new mosquito samples tested positive for West Nile virus. Mosquitos carrying the virus were found in Woodland Hills, Montebello, Santa Fe Springs, and South Whittier. In all, mosquitoes with West Nile Virus have been found within the district's service area to 25 this year. Already, they have been found in Northridge, Reseda, Canoga Park, Winnetka, Carson, Cerritos, Granada Hills, La Mirada, Lakewood, Long Beach, Montebello, Santa Fe Springs, Signall Hill, South Whittier, West Hills, and Woodland Hills.

People infected with the virus can experience a myriad of symptoms, ranging from no symptoms to seizures and death. West Nile virus is a leading cause of severe infections of the nervous system among adults older than age 50 in Los Angeles County. WNV is transmitted to people and animals through the bite of an infected mosquito. There is no cure for WNV.  One in five persons infected with the virus will exhibit symptoms, which can include fever, headache, body aches, nausea, or a skin rash. These symptoms can last for several days to months. One in 150 people infected with the virus will require hospitalization. Severe symptoms include high fever, muscle weakness, neck stiffness, coma, paralysis, and possibly death.

So far this year, 57 WNV human cases have been reported in California, four of which were identified by the Los Angeles County Department of Public Health.

Weekly Update of WNV cases in California available at:

http://www.westnile.ca.gov/