Dengue fever, a mosquito-borne viral disease, has long been a major public health challenge in tropical and subtropical regions worldwide. Yet, strangely enough, despite available vaccines, dengue cases and outbreaks are not only growing but are becoming bigger and less anticipated. This troubling trend has puzzled scientists, medical professionals, and policy makers as well. In order to grasp why dengue keeps spreading despite advances in medicine, we need to look at the intricate entanglement of viral biology, limitations of vaccines, environmental factors, and human drivers behind this worldwide health emergency.

The dengue virus causes dengue fever, spread mainly by the Aedes aegypti mosquito, an insect wonderfully specialized to live in human surroundings. Although it usually manifests with flu-like symptoms like fever, headache, and joint pain, severe cases can progress to dengue hemorrhagic fever—defined by blood vessel destruction, bleeding, organ failure, and even death. The virus comes in four different serotypes (DENV-1 to DENV-4), each of which can cause infection. Significantly, infection with a single serotype provides immunity to only that serotype, not the others, so individuals can be infected as many as four times in a lifetime. Secondary infections tend to carry an increased risk of serious symptoms.

Dengue cases varied historically with periodic epidemics. Recent decades have witnessed a steady and worrisome rise. In 2019, the number of reported cases was a record high, nearly doubling that of the previous year. Bangladesh witnessed a record number of deaths due to dengue in mid-2023. This spread and increase go beyond the classical tropical regions; the Aedes aegypti mosquito has also spread its geographical range into southern Europe and the United States, in Florida, Texas, and Arizona, due to its ability to adapt and global warming.

Are Dengue Vaccine So Irrelevant In Treatment?

Vaccination should theoretically cut disease incidence. New vaccines such as Qdenga have been approved by the World Health Organization for use in children in heavily endemic locations. India is set to introduce DengiAll, its local tetravalent vaccine, in the final stages of trials, which promises to cut dengue cases hugely locally.

However, as Dr. P. Venkata Krishnan, Senior Consultant in Internal Medicine, explains, "Even with the availability of dengue vaccines, cases worldwide are setting new records. This confusing trend suggests underlying issues, from lack of access to vaccines to mosquito spread due to climatic conditions, which require immediate attention beyond vaccination programs to actually contain the epidemic."

One is vaccine coverage and eligibility. The initial dengue vaccine, Dengvaxia, is only approved for those 9–16 years old who have already been infected with dengue. Giving it to dengue-naïve persons risks outcome of severe disease with subsequent infection, limiting its widespread use. Qdenga provides approximately 80% protection and less limitation but is not yet available worldwide. The complexity of dengue serotype diversity makes vaccine design and efficacy even more difficult. Protection against one serotype does not ensure immunity against others, and secondary infection can intensify disease severity.

How Far Do Environmental and Social Factors Push Dengue Diagnosis?

Dengue's spread is not just a medical or biological issue—it is inextricably linked with our environment and society. Dengue has been propelled by rapid urbanization that developed high-density human populations where Aedes mosquitoes breed so abundantly. The mosquitoes breed in small collections of water, even as small as a bottle cap, so controlling them is very difficult.

"Rapid urbanization, inadequate sanitation, and climate change have raised the number of breeding sites for mosquitoes," says Dr. Krishnan. "Increased temperatures and rainfall create perfect breeding conditions for Aedes mosquitoes, boosting their density and the transmission rates of the virus."

Climate change, with increasing global warming and unstable rain patterns, has increased the geographical distribution and breeding periods of mosquitoes. Increased humidity and higher temperatures provide optimal conditions, as in Bangladesh, where premature rains and heat brought a rapid increase in mosquito infestation, resulting in a widespread outbreak of dengue fever.

What are the Challenges in Mosquito Control?

Improved mosquito control is still the bedrock of dengue prevention but is woefully absent in large parts of affected countries. Surveys have reported as high as 49.76% mosquito breeding site prevalence measured in terms of the 'house index' well above the 10% so-called safety level. This indicates poor infrastructure, absent public health interventions, and meager resources available in most of the countries battling dengue.

This provides a perfect storm- high populations of mosquitoes, high human hosts density, and generalized viral transmission, enabling the virus to be transmitted at high speed.

Is Human Behavior and Globalization A Risk Factor Too?

Human activities also contribute to the spread of dengue. Urbanization and population growth add breeding sites and human-mosquito contact. The virus and eggs of mosquitoes can be carried by travelers from one continent to another. Used tires or containers with water can transport mosquito eggs around the world, spreading Aedes mosquitoes to new regions.

Tourism also has a major role to play; dengue now ranks as the second most frequent cause of feverish illness among travelers following malaria. Human mobility and mosquito flexibility facilitate dengue's spread worldwide.

Vaccines hold out promise, but they alone are not the answer. "Vaccines are a key tool against dengue," Dr. Krishnan contends, "but presently available constraints, combined with environmental, social, and infrastructural constraints, have enabled dengue to keep on rising across the world."

It calls for an integrated strategy- the enhancement of mosquito control programs, sanitation in urban areas, community awareness, expenditure on climate adaptation planning, and the quickening of vaccine availability.

In high-income nations, widespread indoor living minimizes contact with mosquitoes, capping outbreaks. In low- and middle-income tropical countries, where individuals tend to reside in open or vernacular housing, the situation is not the same.

Dengue fever's increasing incidence in the presence of vaccines illustrates the intricacy of controlling infectious disease in an integrated, warming world. The interrelationship of viral heterogeneity, restricted vaccine penetration, climate change, urbanization, and inadequate mosquito control generates intractable challenges. Global dengue control requires an integrated strategy that incorporates medical technology with environmental management and improvement of social infrastructure.

It is only through such concerted action that we can hope to stem the tide of dengue fever and protect millions around the world from this increasingly unstable and lethal disease.

Dr. P. Venkata Krishnan is a Senior Consultant, Internal Medicine at Artemis Hospitals, Gurugram in India

An international team of researchers has developed an artificial intelligence (AI)-based tool that can significantly improve care for glaucoma -- a leading cause of irreversible blindness worldwide, according to a study published in The Lancet Primary Care journal today.

Researchers led by those from the University of Lisbon in Portugal found that the AI-based screening tool halved the number of unnecessary referrals for glaucoma.

The study, released during the Glaucoma Awareness Week, also showed an accuracy level at par with human eye doctors.

"The high accuracy at excluding people without glaucoma is especially important, as false alarms can lead to unnecessary hospital visits, patient anxiety, and added strain on healthcare services," the researchers said.

According to the researchers, AI-based screening could:

• support earlier detection,
• reduce unnecessary specialist referrals,
• prevent avoidable vision loss,
• can be integrated into routine primary care in a cost-effective way

Key Findings

The study was carried out at a single screening center in Lisbon, Portugal, in 2023.

The experts screened 671 adults aged 55-65 for glaucoma via the AI tool, analyzing images of the eyes. The images were then independently graded by six glaucoma experts.

The AI-tool:

• referred 66 people (9.8 percent) vs 118 referrals (18.0 percent) by the eye doctors,
• diagnosed glaucoma in 40 participants (6.4 percent).
• It correctly identified 78 percent of people who truly had glaucoma, vs 75 percent identified by the eye doctors
• Correctly ruled out the disease in 95 percent of people, vs 91 percent by eye doctors

While modelling studies suggest that screening could substantially reduce glaucoma-related visual impairment and blindness, barriers include the need for specialised diagnostic equipment and trained personnel, particularly in low- and middle-income countries, and the intrinsically low positive predictive value of screening tests.

In such a scenario, the new study showed that "AI may provide a more viable option than population-wide screening", which may seem impractical.

What Is Glaucoma?

Glaucoma is a chronic disease that affects an estimated 80 million individuals globally, according to the World Glaucoma Association.

It is a progressive, degenerative disorder of the optic nerve that produces characteristic visual field damage.

The disease stems from a long asymptomatic phase, resulting in substantial underdiagnosis and delayed treatment.

Even in high-income countries, up to 50 percent of individuals with glaucoma remain undiagnosed, frequently presenting moderate to advanced disease at first detection.

By the year 2040, it is estimated that there will be 22 million individuals worldwide who are blind from glaucoma.

When to see a doctor for glaucoma:

• Vision suddenly gets blurry
• Severe eye pain
• Headache
• Nausea
• Vomiting
• Rainbow-colored rings or halos around lights

In adults, long periods of sleep deprivation has been linked to problems such as weakened immunity, weight gain, depression, and an increased risk of dementia. However, scientists are now paying closer attention to how sleep affects the brain much earlier in life.

However, a new University of North Carolina School of Medicine study suggests that disrupted sleep during early childhood may interfere with key stages of brain development and asl well as increase the risk of developing autism.

Why Sleep Matters For The Developing Brain

Sleep plays a crucial role in helping these synapses form and strengthen. During sleep, the brain organizes and stabilizes these neural connections, shaping the foundation for future brain function. If sleep is repeatedly disrupted during this delicate stage of development, the process may be affected.

Frequent waking or sleep disturbances could interfere with how these neural connections are formed, potentially influencing behavior and cognitive abilities later in life.

The Link Between Sleep And Autism

“The unique effects of sleep loss during development are largely unexplored,” Diering said. “Our data show that babies and children are more vulnerable to the negative effects of sleep disruption. We also found that sleep loss during this crucial period of time can negatively interact with underlying genetic risk for autism spectrum disorder.”

Sleep problems are already known to be common in people with autism. In fact, sleep disruption has been reported in more than 80 percent of individuals with autism spectrum disorder. However, researchers have long debated whether these sleep issues are a cause of the disorder or a consequence of it. Understanding how sleep interacts with brain development could help scientists detect autism earlier and potentially develop new treatment strategies.

Studying Sleep Disruption In Early Life

In earlier work conducted in 2022, researchers examined how sleep disruption during early life might interact with genetic factors linked to autism. Using mouse models, they disrupted sleep during the third week of life, a developmental stage roughly comparable to ages one to two in humans.

The study found that sleep disruption during this period produced long lasting behavioral changes. Male mice that were genetically vulnerable to autism showed deficits in social behavior later in life. These results suggested that sleep disruption during critical stages of development may interact with genetic risk factors in ways that shape long term behavior.

Younger Brains Respond Differently To Sleep Loss

To investigate further, researchers studied how developing and adult mice respond differently to sleep deprivation.

Using specially designed housing systems equipped with sensitive sensors, scientists tracked the animals’ breathing and movement. This allowed them to determine when the mice were awake and when they were asleep.

The researchers observed that adult mice were able to compensate for lost sleep. After experiencing sleep deprivation, the adults increased their sleep later during their normal active period. This process, known as sleep rebound, allowed them to recover some of the lost rest.

Younger mice behaved very differently. They showed no sleep rebound at all, meaning they did not compensate for the sleep they had lost. This finding suggests that younger brains may be far more vulnerable to the effects of sleep disruption.

The consequences were also visible in cognitive performance. Sleep deprived young mice performed poorly on learning and memory tasks, while adult mice were significantly more resilient after losing sleep.

Changes At The Level Of Brain Synapses

The results showed that sleep deprivation in young mice significantly altered the formation of synapses. These changes were not seen in adult mice. “This now provides one of the largest and most comprehensive datasets to examine the molecular effects of sleep loss across the lifespan,” Diering said.

Potential Future Treatments

“Development is not something that one can go back and do again,” Diering said. “Sleep is important for the entire life and especially during development. Understanding what we know now will place greater emphasis on understanding sleep issues in ASD and could lead to an important therapeutic avenue to treat ASD and other developmental conditions.”

The findings highlight an important message for parents and caregivers. During early childhood, healthy sleep patterns may play a critical role in shaping the brain for years to come.

Using amphetamines, cocaine and cannabis can significantly increase your risk of having a brain stroke particularly among younger adults, according to a new University of Cambridge analysis

The findings highlight how recreational drug use may contribute to a preventable health risk, especially among people under the age of 55.

Megan Ritson, a stroke genetics researcher at the University of Cambridge and lead author said the results provide strong evidence linking certain drugs to stroke risk.

“These findings provide compelling evidence that drugs like cocaine, amphetamines, and cannabis are causal risk factors for stroke,” Ritson noted.

A stroke occurs when blood flow to part of the brain is interrupted. This can happen when a blood vessel becomes blocked by a clot, known as an ischemic stroke, or when a blood vessel bursts and causes bleeding in the brain, known as a hemorrhagic stroke. Both types can lead to serious brain damage and can be life threatening.

Amphetamines Associated With The Highest Risk

When researchers combined data from eight previous studies, they found that recreational amphetamine use was associated with more than double the risk of stroke across all adult age groups. For individuals under the age of 55, the increase was even greater. In this group, amphetamine use was linked to nearly triple the risk of stroke compared with people who do not use the drug.

Across all age groups, the analysis found that amphetamine use increased the risk of ischemic stroke by 137 percent and hemorrhagic stroke by 183 percent. These figures reflect relative risk, meaning the probability of stroke is higher among users compared with non users.

Cocaine Shows A Similar Pattern

The analysis showed that cocaine use nearly doubled the risk of stroke of any kind and more than doubled the risk of hemorrhagic stroke. Additional genetic investigations were conducted alongside the main analysis to better understand whether the relationship might be causal rather than simply linked to other lifestyle factors.

Eric Harshfield, a genetic epidemiologist at the University of Cambridge, said the findings suggest the drugs themselves may play a direct role. “Our analysis suggests that it is these drugs themselves that increase the risk of stroke, not just other lifestyle factors among users,” Harshfield said.

Cannabis Linked To Smaller But Significant Risk

Among people under the age of 55, cannabis use was linked to a 14 percent increase in stroke risk. Although the increase is lower than that associated with stimulant drugs, researchers say it remains important because cannabis is widely used.

Opioids Showed No Clear Association

A Preventable Health Risk

The researchers also note that many of the studies included in the analysis relied on participants reporting their own drug use. Because of this, other lifestyle factors could potentially influence the results. Further research will be needed to better understand the biological mechanisms involved and how different patterns of drug use may affect stroke risk. Still, scientists say the evidence now available provides an important foundation for future public health strategies.

“These findings give us stronger evidence to guide future research and public health strategies,” Ritson said.