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.

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.

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

On May 15, 2025, Japan's Sakurajima volcano erupted and sent a massive ash plume which soared 3,000 metres above the crater. This information has been confirmed by the Japan Meteorological Agency (JMA).

Ever since, the JMA has maintained a Level 3 volcanic alert, which warns people to stay away from the volcano. Ash fall is also expected in surrounding areas, including in areas Kagoshima, Kumamoto, and Miyazaki.

While it is a natural disaster, however, this also impacts one's health. Let us look at how can volcanic eruption can impact one's health.

Volcanic Eruptions' Impact On Health

As per the Centers for Disease Control and Prevention (CDC), volcanoes are geographical formations where lava, small rocks, and steam are released onto the surface of the earth.

When a volcano erupts, it can release harmful particles, including volcanic gases and ash, into the air. These volcanic gases may have an adverse impact on your health, including:

• Carbon Dioxide (CO2)
• Sulfur Dioxide (So2)
• Hydrogen Chloride (HCL)
• Hydrogen Sulfide (H2s)
• Radon (Rn)
• Hydrogen Fluoride (HF)
• Sulfuric Acid (H2SO4)

How Each Toxic Gas Impacts Health

Carbon Dioxide

As per the USDA Food and Safety Inspection Service, CO2 is colorless, odorless, non-flammable gas that naturally occurs in the atmosphere. As the CDC mentions, it is also released when a volcanic eruption takes place. CO2 is considered to be minimally toxic by inhalation. The primary health effects caused by CO2 are the result of its behavior as a simple asphyxiant.

A simple asphyxiant is a gas which reduces or displaces the normal oxygen in breathing air.

Symptoms of mild CO2 exposure may include headache and drowsiness. At higher levels, rapid breathing, confusion, increased cardiac output, elevated blood pressure, and increased arrhythmias may occur. Breathing oxygen-depleted air caused by extreme CO2 concentrations can lead to death by suffocation.

Sulfur Dioxide

As per the National Park Service, Sulfur dioxide is a colorless, reactive air pollutant with a strong odor. This gas can be a threat to human, animal and plant health.

It can irritate the skin and mucous membranes of the eyes, nose, throat, and lungs. High concentrations of SO2 can also cause inflammation and irritation of the respiratory system. This can then lead to pain when taking deep breaths, coughing, throat irritation and breathing difficulties. This gas can further affect lung function, worsen asthma attacks, and exacerbate existing heart diseases.

Hydrogen Chloride

As per the CDC, hydrogen chloride is a colorless to slightly yellow gas with a pungent odor. On exposure to air, the gas forms dense white vapors due to condensation with atmospheric moisture.

Upon inhalation, the odor could irritate and affect the lungs. While it cannot be absorbed through the skin, its direct contact could irritate the skin and cause chemical burns. The ingestion could also lead to corrosive injury to the lips, mouth, throat, esophagus, and stomach.

Hydrogen Sulfide

As per the US Department of Labor, hydrogen sulfide causes a wide range of health effects, especially if you breathe it and are exposed to it for a longer duration. Its exposure to very high concentrations could also lead to death.

It is a highly flammable, explosive gas, and can cause a life-threatening situation when not handled properly. Its exposure to skin can cause "blue skin" or frostbite.

Radon

As per the US Environmental Protection Agency, radon could lead to lung cancer. It is also the number one cause of lung cancer among non-smokers.

Hydrogen Fluoride

As per the CDC, it is also a colorless gas or liquid that could cause severe damage to the body. The effects could also depend on how long one is exposed to the gas. If it is breathed in, it can irritate the eyes and respiratory tract. Breathing in a large amount could cause death from irregular heartbeat or from fluid buildup in the lungs. It can also cause rash and deep, slow-healing burns.

Sulfuric Acid

As per the Department of Climate Change, Energy, the Environment and Water run by the Australian Government, sulfuric acid is the world's largest volume industrial chemical. It is corrosive in nature and can severely burn the skin and eyes. It can also cause third-degree burns and blindness on contact. It can also irritate the eyes, nose, throat, and lungs.