In 2025, thanks to climate change, rapid urbanization, and frequent travels, new viruses, their strains, and infections have spread frequently. Infections have affect millions and some diseases have come back with their new strains, which have been more contagious, whereas other diseases are finding new ways to emerge.

As we look back at the year, which is about to end in just another month, let us look back at the top 5 infectious diseases of 2025.

Respiratory Infections

In 2025, respiratory infections were the most widespread, with new COVID-19 variants emerging every now and then. Along with this common flu too has emerged. This has weakened immunity and made elderly and infants, and people with comorbidities more vulnerable to the diseases.

The new COVID variants in India are linked with the JN.1 variant and its sub-variants like LF.7 and NB.1.8. The COVID variants in the UK which were active were XFG, NB.1.8.1, or known as the Stratus and Nimbus variants. Other variants were XFG.3, XFG.5, and XFG.3.4.1.

Tuberculosis (TB)

Tuberculosis still continues to be a major infectious disease in 2025, especially in countries like India. As per the World Health Organization (WHO), tuberculosis caused 1.25 billion deaths in 2023. It becomes the world's leading infectious disease after COVID-19.

Each day, close to 3,425 people lose their lives to TB, and close to 30,000 people fall ill with this preventable and curable disease. About 10.8 million people got TB in 2023, which include 6 million, 3.6 million women, and 1.3 million children.

Dengue and other mosquito-borne infections

Mosquito-borne diseases like dengue, chikungunya, malaria, and Zika continued to rise in 2025. The reason being changing weather patterns. Dr Sanjeev Bagai, Chairman of Nephron Clinic, and Senior Consultant Pediatrician and Nephrologist points out that earlier the mosquito-borne diseases were seasonal, however, due to rapid urbanization and climate changes, these diseases have stayed all round the year.

Hepatitis Infections

Hepatitis B and Hepatitis C are among the most common Hepatitis infections in 2025. However, there have been outbreaks of Hepatitis A and E in unsafe water and food. Chronic hepatitis can also damage liver and also lead to cancer. It is a concern because it spreads through contaminated food, unsafe water, blood, and sexual contact. While many people may not show symptoms until serious liver damage occurs.

Symptoms also include jaundice, dark urine, fatigue, nausea, and abdominal pain.

Gastrointestinal Infections

Food- and water-borne infections are still common across the world. Illnesses like salmonella, cholera, rotavirus, and norovirus often spread in areas where hygiene, sanitation, and food safety are poorly maintained.

Why are these infections risky?

They can spread extremely fast, especially among children and older adults. Severe diarrhea and vomiting can lead to dangerous dehydration if not treated in time.

What symptoms should you look out for?

Persistent diarrhea, vomiting, stomach cramps, fever, and signs of dehydration. The best prevention is simple: drink clean water, wash hands regularly, and eat properly cooked food.

While doctors across the world recommend ensuring that fluoride and other protective minerals make up your toothpaste, your body produces its very own amino acid that protect your entire dental cavity.

Arginine, an amino acid that is already present in saliva, can turn bacteria from damaging to protective in your mouth, a study has found.

When sugars from food are broken down by the many bacteria living in the mouth, acids are produced that gradually damage tooth enamel and lead to cavities. This is known as dental caries. Over time, this acid dissolves tooth enamel and causes cavities.

However, researchers at Aarhus University in Denmark have discovered that regular arginine treatment can significantly reduced the overall acidity levels in the mouth and prevent tooth decay.

Yumi Del Rey, microbiologist at Aarhus, said: ""Our results revealed differences in acidity of the biofilms, with the ones treated with arginine being significantly more protected against acidification caused by sugar metabolism."

How Did The Study Take Place?

Volunteers were then asked to instructed to dip the dentures in a sugar solution for 5 minutes, immediately followed by distilled water (as placebo) or arginine for 30 minutes, one on each side. This was to be repeated three times a day, with arginine treatment done on the same side each time.

Sebastian Schlafer, professor at the Department of Dentistry and Oral Health, explained: "The aim was to investigate the impact of arginine treatment on the acidity, type of bacteria, and the carbohydrate matrix of biofilms from patients with active caries."

After 4 days of this process, the biofilms were developed and the dentures were removed for detailed analysis. The researchers compared dental plaques grown on customized dentures on both sides of each participant's mouth using a special pH-sensitive dye called C-SNARF-4.

How Does Arginine Work?

Additionally, the team also began to look into how arginine might be reducing acidity, by taking stock of which bacteria and sugars were present in each sample.

Biofilms treated with arginine showed lower levels of a sugar called fucose, while another sugar, galactose, was concentrated towards the outer surface of the biofilm, meaning both sugars were away from the tooth enamel.

After analyzing the DNA of bacteria present, the researchers found that arginine treatment significantly reduced a specific population of Streptococcus bacteria known to produce acid, while slightly increasing other bacterial strains that can metabolize arginine.

The scientists noted that while more research is needed into the arginine's effectiveness, the amino acid could be a promising new addition to oral hygiene products such as toothpaste or mouthwash.

Covid is returning, as the National Health Service, NHS UK warned that there has been a "bounce back" in respiratory viruses this winter, along with COVID too on the rise. While UK was already struggling with flu and norovirus on the rise, cases of COVID have also risen. The latest data from the UK Health and Security Agency (UKHSA) show that the number of patients in hospital beds with COVID per day has risen from 0.87 per 100,000, as compared with 0.77 per 100,000 the previous week.

NHS national medical director Professor Meghana Pandit said: “It’s clear that the worst is far from over for the NHS this winter, with hospitals again experiencing a rise in patients admitted with flu and other respiratory virus cases last week.”

What New COVID Variants Are We Dealing With In 2026?

Since the pandemic, there have been many variants of COVID. The virus has continued to evolve. Two new variants that caused the spike in cases in autumn were XFG, known as Stratus, and NB.1.1, known as Nimbus.

Stratus: It is a subvariant of Omicron variant and made of previous variants LF.7 and LP.8.1.2. It was first detected in a sample on January 27, 2025. Whereas, Nimbus was first detected on January 22, 2025. It also originated from the same omicron variant, which was the reason for spike in 2023.

The World Health Organization (WHO) describes stratus as a "variant under monitoring" after several countries in South East Asia reported a rise in new cases and hospitalizations with this variant being detected.

COVID Symptoms 2026: Fatigue Emerges As The Most Common Symptom

Among studies that focused on how symptoms appear together, fatigue stood out as the most consistently reported issue. It often occurred alone or alongside problems such as muscle and joint pain, brain fog, or breathlessness. Other symptom pairings that appeared frequently included loss of smell and taste, anxiety with depression, and various forms of musculoskeletal pain.

When researchers classified patients based on affected organ systems, respiratory problems were the most widespread, seen in about 47% of long COVID patients. Neurological symptoms followed at 31%, while gastrointestinal issues were reported by 28%. The authors stressed that these percentages reflect how often these clusters appeared within long COVID cases studied, not how common they are in the general population.

A smaller number of studies sorted patients by how severe their symptoms were, dividing them into mild, moderate, or severe categories using symptom scores, symptom counts, or quality-of-life measures. Three studies used clinical indicators for classification, including abnormal triglyceride levels and signs of restricted lung function on imaging.

As per the Centers for Disease Control and Prevention (CDC), here are the common COVID symptoms:

• Fever or chills
• Cough
• Shortness of breath or difficulty breathing
• Sore throat
• Congestion or runny nose
• New loss of taste or smell
• Fatigue
• Muscle or body aches
• Headache
• Nausea or vomiting
• Diarrhea

How To Know If You Have COVID?

CDC says, look out for these signs:

• Trouble breathing
• Persistent pain or pressure in the chest
• New confusion
• Inability to wake or stay awake
• Lips and nail beds may appear pale, grey or blue

Have you ever dread waking up in the morning and felt like you just need the five extra minutes of sleep? Study now shows that it can actually be helpful for your health. A study published in the Lancet journal eClinical Medicine suggests that seven to eight hours of sleep per day, more than 40 minutes of moderate to vigorous physical activity and a healthy diet is associated with over nine years of additional lifespan and years spent in good health.

“The combined relationship of sleep, physical activity, and diet is larger than the sum of the individual behaviors. For example, for people with the unhealthiest sleep, physical activity and dietary habits to achieve one additional year of lifespan through sleep alone would require five times the amount of additional sleep per day (25 minutes) than if physical activity and diet also improved a small amount,” said the international group of researchers from the UK, Australia, Chile, and Brazil.

In a separate study published in The Lancet, researchers from Norway, Spain, and Australia found that adding just five extra minutes of walking to a daily routine can reduce the risk of death by 10 percent for most adults. The study reported that it will also help the least active adults to reduce their risk of death by around 6 per cent.

How Was The Study Conducted?

The study, which analyzed data from over 135,000 adults, found that cutting sedentary time by just 30 minutes a day was linked to a 7 percent reduction in overall deaths if adopted by most adults who sit for around 10 hours daily. Among the most sedentary people, who sit for about 12 hours a day, deaths could fall by nearly 3 percent.

“These estimates show the broad public health impact of even small, positive changes in physical activity and reduced inactivity,” said corresponding author Prof Ulf Ekelund of the Norwegian School of Sport Sciences, Oslo.

Researchers stressed that the findings are not meant as personalized advice, but as evidence of potential benefits at a population level.

Speaking to The Indian Express, Dr Nicholas Koemel from the Mackenzie Wearables Hub at the Charles Perkins Centre, University of Sydney, leading researcher of another study that seconds that extra five minutes of sleep can in fact help people live longer, said, "While major lifestyle overhauls are often recommended, they may not always be achievable or sustainable. Our results suggest that modest, combined changes may offer meaningful health benefits, be more likely to be maintained over time and provide an important starting point for individuals who may otherwise find it difficult to initiate lifestyle change. Starting by reviewing our daily routines to identify where small, realistic tweaks can be made is an important first step towards improving long term health and longevity."

Research over the years has consistently shown that moderate to vigorous physical activity helps improve key markers of health, including blood pressure, blood sugar, body weight, and body fat. Building on this, a large multi-country analysis of cohort data explains that even small increases in daily physical activity can significantly reduce the risk of death from any cause. The biggest gains are seen among people who are least active, as regular movement leads to a sharp drop in mortality risk for them. If such habits are adopted widely across the population, the data suggest that nearly 10 percent of deaths in people in their 70s and 80s could potentially be prevented.