Flu cases have started to rise as temperatures drops. Flu or influenza is a contagious viral infection that targets the respiratory system of a person. Key symptoms include fever, chills, cough, sore throat, stuffy nose, body aches, headaches amongst others. Government statistics show that this infection causes 710,000 hospitalizations and 51,000 deaths annually in US.

While for many, the immune system clears the symptoms in about a week, for others, it can lead to severe illness, hospitalization, or even death. A new analysis by the Centers for Disease Control and Prevention (CDC), which examined flu-related hospitalizations from 2010 to 2023, reveals some of the factors that put people most at risk of severe health outcomes.

Age Is An Important Factor

Age plays a crucial role when it comes to immunity. As a result, young children and older adults are consistently hospitalized with the flu at the highest rates, as their bodies find it tough to fend off infections compared to healthy adults.

People with neurological disorders are also at higher risk, especially children. Conditions like epilepsy, cerebral palsy, and ADHD can impair muscle and lung function, making it harder for individuals to cough or clear fluids from their respiratory tracts. This can severely exacerbate flu symptoms or lead to pneumonia.

Flu can also trigger asthma attacks in children with lung diseases. By causing chronic inflammation of the airways, it can lead to pneumonia and other severe illnesses that require hospitalization.

Meanwhile, adults with chronic obstructive pulmonary disease (COPD) find it harder to clear a bout of flu, due to weakened immune response.

Pregnancy Hormones Weaken Immunity

Moreover, research shows that pregnancy hormones weaken the immune system, increasing the risk of severe infections and hospitalizations. According to the CDC, nearly 30% of women of reproductive age who were hospitalized with the flu over 13 flu seasons were pregnant. Notably, contracting the flu while pregnant also poses risks to the fetus.

Obesity is another risk factor for severe illness from the flu in both children and adults. Excess weight can make it harder to take deep breaths needed to clear an infection from the lungs. Obesity is also linked with other metabolic diseases like diabetes and hypertension. In patients with diabetes, a bout of flu can make blood sugar levels harder to control.

According to the CDC, about half of adults hospitalized with the flu have heart disease, which weakens the immune system. Additionally, the flu itself increases the risk of heart attack and stroke in people already suffering from cardiovascular disease.

Flu vaccines have been shown to significantly reduce the risk of hospitalization for both children and adults. A recent study revealed that vaccination decreased the hospitalization rate by 34.5% this year across five South American countries, where flu season arrives earlier. However, experts stress that even if you are vaccinated, it’s important to watch for symptoms that might require medical attention, such as difficulty breathing and chest pain.

The so-called “mystery virus” behind lingering sore throats, blocked noses filled with mucus, and days of exhaustion is actually well known to doctors. According to Eric Sachinwalla, medical director of infection prevention and control at Jefferson Health, the culprit is adenovirus.

What makes this virus particularly difficult to control is how tough it is. Adenovirus can survive soap and water, withstand many everyday disinfectants, and linger on contaminated surfaces for long stretches of time. Below is what experts know so far about this fast-spreading infection.

What Is Adenovirus?

Adenovirus refers to a group of common viruses that usually trigger cold- or flu-like illness. It spreads easily because it is far more resilient than many other viruses. Ordinary soap, water, and standard disinfectants do not reliably destroy it, allowing it to persist in the environment. As a result, infections often cluster in places where people spend time close together, such as daycares and military barracks. The virus spreads through the respiratory tract, can be shed in stool, and can survive for some time on contaminated surfaces, according to the CDC.

Adenovirus: What Are The Symptoms Of Adenovirus?

“Adenovirus is a typical virus that causes common cold or flu-like symptoms,” says Dr Deborah Lee at Dr Fox Online Pharmacy. That does not mean adenovirus is the same as a cold. Instead, adenovirus is one of many germs that can cause cold-like illness. A simple way to think about it is that a “cold” describes the symptoms, while adenovirus is one specific virus that can lead to them.

Symptoms can vary depending on the subtype involved. While there are more than 100 known subtypes, only 49 infect humans. Dr Lee notes that people may experience any of the following:

• Fever
• Runny nose
• Sore throat
• Swollen cervical lymph nodes in the neck
• Cough
• Shortness of breath
• Conjunctivitis
• Ear pain
• Diarrhoea
• Vomiting
• Stomach pain
• Urinary tract infection

Adenovirus? Is It Contagious?

“Adenovirus infection is highly contagious,” Dr Lee explains. “It spreads by breathing in infected droplets, by touching the virus and then rubbing the eyes, or through the faecal-oral route, often due to poor hand hygiene after using the toilet.”

She adds that the virus spreads quickly in crowded settings where people are in close contact. To eliminate adenovirus from surfaces, Dr Lee recommends stronger cleaning agents such as bleach-based solutions or hydrogen peroxide. “The virus is resistant to soap and many commonly used cleaners,” she says.

To reduce the risk of catching adenovirus or other respiratory infections currently circulating, Dr Lee advises staying away from people who are unwell. She also suggests the following precautions:

• Avoid touching your face and nose
• Use a clean tissue to blow your nose and dispose of it immediately
• Wash your hands often with soap and warm water, then dry them thoroughly, especially after using the toilet or changing nappies
• Clean children’s toys regularly
• Disinfect worktops, changing areas, toilets, and bathrooms
• Avoid sharing cups, plates, food, or towels
• Wear a mask if you need to go out while unwell
• Keep windows open and ensure rooms and workspaces are well ventilated.

Dozens of norovirus outbreaks have been recorded nationwide over the past few weeks, and as people deal with intense vomiting, diarrhea, and other uncomfortable or even risky symptoms, a common question keeps coming up: why is there still no vaccine for such a widespread infection.

The Centers for Disease Control and Prevention (CDC) says norovirus cases are increasing toward the end of 2025, with higher activity reported in both the US and the UK. Health officials note that a new, highly infectious strain known as GII.17 is partly driving this rise. Because many people have little or no immunity to it, outbreaks are being seen more often in schools and shared public spaces. While overall case numbers remain within typical seasonal ranges, recent weeks have shown a clear upward trend.

What Is Norovirus?

Norovirus is an extremely contagious virus that leads to gastroenteritis. It commonly causes symptoms such as vomiting, diarrhea, nausea, and stomach cramps, and may also bring fever and body aches. It is often referred to as the ‘stomach flu,’ though it has no connection to influenza.

The virus spreads quickly through contaminated food or water, shared surfaces, or direct contact with an infected person’s vomit or stool. Crowded settings like cruise ships are especially vulnerable. Most people recover within one to three days with rest and enough fluids, according to the CDC.

Norovirus Symptoms 2025

Norovirus usually comes on suddenly, causing vomiting, watery diarrhea, nausea, and abdominal pain. Fever, headaches, and body aches are also common. Symptoms typically appear 12 to 48 hours after exposure and last for one to three days. Because it spreads so easily, infections can move fast through families and communities.

While most cases improve on their own, dehydration is a concern, so warning signs such as intense thirst or reduced urination should not be ignored, as noted by the Cleveland Clinic.

Do We Have A Norovirus Vaccine?

At present, there is no widely available vaccine for norovirus. That said, research has made meaningful strides. Experimental oral vaccines have shown encouraging results in clinical studies, suggesting they may offer protection against multiple fast-changing strains and help reduce how much virus an infected person sheds. Scientists are hopeful that an effective, broadly protective vaccine may become available in the coming years, according to the National Institutes of Health.

Why Don’t We Have a Norovirus Vaccine Yet?

Developing a vaccine for norovirus has proven especially difficult, largely because of how quickly the virus changes. “It really is evolving extremely rapidly, and that’s a big problem,” Patricia Foster, PhD, professor emerita of biology at Indiana University Bloomington, told Health.

Norovirus also exists in dozens of subtypes, with several dominant strains circulating at any given time. This is why people can catch norovirus more than once in their lives. Even if immunity develops against one strain, either after infection or through vaccination, another strain can still cause illness. Centers for Disease Control and Prevention. About norovirus.

Norovirus: Multiple Vaccines Are In The Works

Despite these obstacles, vaccine research is moving forward. Progress has accelerated in part because of newer technologies developed over the past decade. In 2016, Mary Estes, PhD, a researcher at Baylor College of Medicine, and her team found a way to grow norovirus outside the human body. This breakthrough made it possible to test vaccine approaches and treatments more effectively. This step was crucial because common lab animals like mice do not typically get sick from human norovirus.

Today, scientists are testing several experimental vaccines. One example is a 2023 vaccine developed at Washington University School of Medicine in St. Louis that combines protection against norovirus with an existing rotavirus vaccine. Several pharmaceutical companies are also developing candidates, many of which are now in clinical trials, said Amesh Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, in comments to *Health*.

HilleVax, a Boston-based company, has been testing a norovirus vaccine originally developed by Japan’s Takeda. However, that candidate did not succeed in a phase II trial in June 2024. Meanwhile, a tablet-style norovirus vaccine from San Francisco-based Vaxart has completed phase I testing. Among the most promising efforts is Moderna’s vaccine, which is currently being tested in human volunteers.

Preventing Norovirus, Even Without a Vaccine

Norovirus spreads so easily that stopping it once someone falls ill can be very challenging. This is linked to the virus’s structure. Norovirus is a nonenveloped virus, similar to polio and other stomach-related infections. Because of this, neither hand sanitizers nor soap and water actually destroy the virus, Foster explained. “Handwashing helps because you’re physically rinsing the virus away,” she said.

As a result, basic hygiene practices, especially thorough handwashing, remain some of the most effective ways to lower risk, said Ming Tan, PhD, an infectious disease researcher and associate professor of pediatrics at Cincinnati Children’s Hospital Medical Center, speaking to *Health*.

If norovirus does strike, treatment options are limited. Staying hydrated is essential to avoid complications from fluid loss. Some people may also use medicines to control nausea or diarrhea, either over the counter or by prescription, such as Zofran. If severe symptoms develop, including confusion, high fever, or intense abdominal pain, medical care should be sought right away.

Could air pollution be making you grumpy? We know of the harmful impact of air pollution on our health, including various organs and functioning of our body, but can Delhi's worsening AQI impact how we feel?

There has been emerging evidence that point towards the impact of toxic air on psychological wellbeing and brain health. Polluted air can worsen anxiety, depression, heighten stress, and impair cognitive functions. It has raised fresh concerns with regards to air pollution.

In fact, speaking to HT, Dr Astik Joshi, who is Child and Adolescent and Forensic Psychiatrist at Fortis Hospital, Shalimar Bagh, said that worsening air conditions could make us more irritable, lower mood, and lead to depressive symptoms. “Toxic haze from long-term exposure to polluted air, specifically smaller airborne particles found in fine particulate matter such as PM2.5, is known to not only penetrate the blood and cross the blood-brain barrier; but when they reach the brain, they activate inflammatory responses and create oxidative stress, thereby disrupting the normal functioning of the brain," he tells HT.

When polluted air reaches brain, it reduces the levels of oxygen and could even lead to brain inflammation. This can impact in learning and memory areas of brain, and could lead to 'brain fog'.

What Do The Studies Say On Air Pollution And Mood?

A study published in Nature Communication notes that after four hours of exposure to particulate matter, it was found that people's ability to perform routine tasks and interpret emotions were highly impacted.

Study's co-author, Dr Thomas Faherty said, "Study provides compelling evidence that even short-term exposure to particulate matter can have immediate negative effects on brain functions essential for daily activities.”

Among all the cognitive abilities examined, two showed the clearest impact: selective attention and emotion recognition. People exposed to particulate matter air pollution experienced declines in both, regardless of how the polluted air entered their bodies.

Read: British Man Compares Breathing In Delhi To Smoking 18 Cigarettes

Selective attention is central to decision-making and staying goal-focused, while emotion recognition helps us read social cues and respond appropriately to others. When these functions are affected, everyday tasks can suffer. The study illustrates this through something as routine as grocery shopping: reduced selective attention can make it harder to stick to a list, increasing the likelihood of impulse purchases.

The implications stretch far beyond errands. Even brief exposure during a commute or a short walk could temporarily dull cognitive performance. A drop in attention can affect productivity, while impaired emotion recognition may make collaboration, meetings, and everyday workplace interactions far more challenging.

However, contrary to what Dr Joshi said, the study noted that no decline in working memory was seen. This means that some brain functions were quite resilient and are able to avoid the inflammation caused by pollution. However, more research is required to come to this conclusion, as in the study, the PM exposure was controlled and done by a candle smoke.

A 2002 study titled Air Pollution and Brain Damage, noted that long term exposure to air pollution could lead to cognitive disorders including Alzheimer's disease, Parkinson’s disease and multiple sclerosis.