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

Colorectal cancer is no longer an elderly person's disease alone. Over the last few years, a dramatic increase in early-onset colorectal cancer—defined as diagnosis at younger than 50 years old—has warned doctors and scientists globally. Sedentary behavior, unhealthy diets, and environmental toxins have long been suspected factors, but a new study has placed high-profile attention on a sneaky but ubiquitous condition as a new, worrisome contributor: non-alcoholic fatty liver disease (NAFLD).

Affecting up to one in four individuals worldwide, including an estimated 80 to 100 million Americans, NAFLD frequently goes undetected until complications arise. A new population-based cohort study now associates the so-called "silent liver disease" with a greatly increased risk of early-onset colorectal cancer, particularly in men and those in their 20s.

What Is NAFLD and Why Is It a Concern?

NAFLD (Nonalcoholic Fatty Liver Disease) is defined by the build-up of excess fat in the liver that is not related to alcohol use. It is usually asymptomatic, progressing over a long period of time with a possible end point of liver inflammation, fibrosis, or cirrhosis. More recently, it has been linked to systemic inflammation, which scientists now suspect can initiate changes outside the liver—as in, in the colon.

Lifestyle factors like diets rich in sugar and saturated fats, obesity, and metabolic disorders are leading causes of NAFLD. As the worldwide epidemic of these risk factors spreads, NAFLD has become an epidemic of our times—and now, a potential cause of early colorectal cancer.

South Korean researchers conducted a large-scale, population-based cohort study to examine the relationship between NAFLD and risk of colorectal cancer among young adults. The study used health records from more than 4.6 million individuals between the ages of 20 and 49, and followed participants for longer than nine years via the Korean National Health Insurance Service.

NAFLD status was identified by the Fatty Liver Index (FLI)—a clinically validated diagnostic measure. Patients were assigned to three groups:

• No NAFLD (FLI < 30)
• Borderline NAFLD (FLI 30–59)
• NAFLD (FLI ≥ 60)

During the follow-up period, 2,733 people developed early-onset colorectal cancer.

The research discovered that people with NAFLD were 24% more likely to get early-onset colorectal cancer than those with no liver fat. Even study participants who had borderline NAFLD experienced a 12% higher risk.

Moreover, the researchers observed a dose–response relationship: the more severe the fatty liver, the higher the risk of cancer. The association was especially strong in:

• Males
• Young adults aged 20–29
• Those without diabetes

This population-based finding emphasizes the necessity for targeted early screening and prevention measures, particularly in these high-risk groups.

How NAFLD is Linked to Colorectal Cancer?

NAFLD doesn't only impact liver health, it induces systemic alterations that could account for its association with colorectal cancer:

• Persistent liver inflammation releases cytokines—immune signaling proteins that have the potential to encourage cancer cell proliferation.
• DNA damage in colon cells could be a consequence of liver inflammation being carried systemically.
• NAFLD influences bile acid production, which subsequently could disrupt the gut microbiome—a recognized risk factor for colorectal cancer.

The research discovered a specific rise in tumors in the left colon and rectum, indicating a focused effect, although the precise biological process is unknown.

Why Early Screening is Imperative?

Today, most national screening guidelines advise starting colorectal cancer screening at age 50 or 45. But this study refutes that cutoff—particularly for younger individuals with evidence of NAFLD. The scientists highlighted the need for "multifaceted preventive strategies" including:

• Lifestyle modifications to decrease liver fat
• Increased screening programs for colorectal cancer in individuals with NAFLD—even if they are below 50 years old
• Heightened awareness among primary care providers and the public regarding NAFLD's risks

Although the study was strong, researchers noted various limitations. These include not having data available on family history of colorectal cancer, stage of diagnosis, and prior colonoscopy screening. Additional international studies, especially in Western populations, are necessary to confirm and build on these findings.

Nevertheless, the evidence points to a key blind spot in existing cancer prevention strategy—a one that public health systems might need to tackle urgently.

This research adds valuable insight into our knowledge of how colorectal cancer is on the increase in young groups. It supports the theory that subtle inflammation elsewhere in the body, such as in the liver, which becomes apparent at a younger age, can lay the groundwork for later cancer development elsewhere.

Working long hours may alter the structure of the brain, a new study has found. The research, published in the journal Occupational and Environmental Medicine, found "significant changes" in the brains of people who were overworking. These changes were observed in the grey matter of the brain, which is the most essential type of tissue in the brain and spinal cord.

For the study, researchers observed the impact of overwork on specific regions in health workers who regularly clocked up more than 52 hours a week. Around 110 workers were included in the final analysis. Of these, 32 worked excessive hours and 78 worked standard hours.

The scientists found that being "overworked" could significantly impact mental health. The researchers used data, including MRI scans, to examine brain structure. "People who worked 52 or more hours a week displayed significant changes in brain regions associated with executive function and emotional regulation, unlike participants who worked standard hours," researchers said in a press release. "The results underscore the importance of addressing overwork as an occupational health concern and highlight the need for workplace policies that mitigate excessive working hours," they added. Besides emotional regulation, decision-making and planning were also equally impacted.

Epidemic Of Long Working Hours

Researchers also believe that their findings suggest a "potential relationship" between having an increased workload and challenges in these parts of the brain, providing a biological basis for the cognitive and emotional challenges reported by overworked people. According to SkyNews, Ruth Wilkinson, head of policy and public affairs at the charity the Institution of Occupational Safety and Health, said urgent action is needed to tackle "an epidemic of long working hours".

Cognitive fatigue is the deterioration in the ability to effectively and focus effectively. It is primarily caused by prolonged mental work. Many workers might spend their days completing a lot of tasks that aren't urgent or necessary, but do create lots of vacuums of time and mental energy to respond to. Cognitive fatigue occurs when we make many more micro decisions in the day than we need to, and there are so many different touchpoints that grab our attention in an office. These could be noise, colleagues, phones, Slack or meetings.

World Health Organisation (WHO) has declared a polio outbreak in Papua New Guinea and called for an "immediate" vaccination campaign. Samples of the highly infectious virus were found in two healthy children during a routine screening in Lae, a coastal city in the country's northeast.

Less than half of the country's population are immunised against the potentially deadly disease, which is close to being wiped out, but has recently surfaced in some parts of the world. "We have to do something about it and we have to do it immediately," said Sevil Huseynova, WHO's representative in Papua New Guinea, warning that the disease could spread beyond the country. We have to make maximum effort to get 100% [vaccination] coverage," Dr Huseynova said at a media conference on Thursday. Polio knows no borders.

Polio is highly contagious and can be transmitted through droplets from sneezing or coughing, as well as through contact with virus-laden faeces, also known as stool. The virus can easily spread and enter the body through the mouth, and it can also be present in water contaminated with feces from a person infected with the poliovirus. In 1994, India launched the Pulse Polio Immunisation Program to eradicate polio, which at the time accounted for about 60% of global cases. In January 2011, the last reported cases of wild polio in India were in West Bengal and Gujarat. Subsequently, in 2014, the WHO declared India polio-free.