The human immune system is a remarkable defense mechanism, capable of protecting us from an array of diseases. Yet, while some illnesses like measles or mumps often grant lifelong immunity, others, like the flu, require annual vaccinations. It is not simply interesting to know why immunity may differ among the various diseases but also shows how our immune system works in intricate detail and can teach us a lot about better control over recurring infections.

At its core, immunity is a highly complex response involving antibodies, special proteins the immune system produces to attack and neutralize the dangerous pathogens. During an infection, it manufactures antibodies to coat the invading cells, so that they cannot hijack and replicate within our cells.

Even after the infection is cleared, some antibodies remain in our system, ready to defend against future encounters with the same disease. These lingering antibodies are the reason why antibody tests can reveal past infections and why we’re often protected from reinfection—at least in some cases.

Why Immunity Lasts for Some Diseases?

Immunity for diseases such as measles, polio, or mumps lasts much longer because of the nature of the pathogens and the immune response they provoke. In a study published in the New England Journal of Medicine in 2007, researchers reported that antibodies against measles and mumps were detectable for more than 200 years, effectively giving lifelong protection.

Long-term immunity is thought to result from several factors:

1. Pathogen Stability: Some viruses, such as the polio virus, are genetically stable and do not mutate easily. This stability allows the immune system to always recognize and neutralize the pathogen.

2. Strong Immune Response: These diseases usually elicit a strong antibody response, ensuring that even small amounts of antibodies can prevent reinfection.

3. Reinfections Enhance Immunity: For some infections, reinfections may happen as an asymptomatic occasional occurrence, yet they keep the immune system vigilant by maintaining active production of antibodies.

Also Read: Not Boosted But A Balanced Immune System Is The Secret To Good Health

Why Other Diseases, Such As the Flu Cycle Every Year

In contrast to this, flu virus is more challenging. With yearly vaccinations, the flu becomes a seasonal disease. This year in and out cycle is a result of a remarkable mutation mechanism of the flu virus.

Genetic Mutations and Antigenic Drift

The flu virus constantly changes its genetic makeup due to a process called antigenic drift. This results in changes to the virus's surface proteins, which can no longer be recognized by the immune system. This means that even if you were immunized against last year's flu strain, your immune defenses might not recognize this year's version.

Immune System Prioritization

The immune system also responds less vigorously to infections of the upper respiratory tract, such as the common cold and mild influenza. Since these infections are rarely severe, the body does not need to produce large quantities of antibodies to fight them off.

COVID-19 Immunity and What Makes it Different from the Flu?

The novel coronavirus, SARS-CoV-2, occupies a unique position in this discussion. In contrast to the flu, SARS-CoV-2 does not mutate as quickly, which is a hopeful indicator for long-term immunity. Preliminary evidence from vaccine trials and natural infections indicate that most individuals develop neutralizing antibodies—that is, antibodies that prevent the virus from entering cells.

However, it is still to be seen if the immunity to SARS-CoV-2 is long-term or will we have to take boosters every year as we do with flu. Scientists are optimistic that immunity to COVID-19 will be like that of diseases like measles since the mutation rate of the virus is relatively low.

Why Do Some Antibodies Survive Longer Than Others?

The longevity of responses depends not merely on the characteristics of the invading pathogen, but also of its structure. So, pathogens characterized by symmetries and repititions cause a more persistent infection, like for example the one caused by smallpox viruses. Diseases in contrast, produced by toxins due to bacteria alone, like the tetanus-induced disease, entail periodic booster vaccines to ensure enduring immunity.

This theory underscores the complex relationship between a pathogen's structure and the immune system's ability to remember and respond effectively.

Implications for Vaccination Strategies

The differing lengths of immunity point to the need for individualized vaccination strategies. For stable diseases like measles, one immunization is enough to ensure long-term protection. For diseases with high mutation rates, such as the flu, constant surveillance and annual vaccine updates are required to keep pace with changing strains.

COVID-19 vaccination efforts provide a unique case study. The development of vaccines that elicit strong, neutralizing antibody responses provides hope that periodic boosters may suffice, rather than yearly updates. Continued research will be crucial in determining the best course of action.

The immune system’s ability to grant lasting protection or allow reinfection is a delicate balancing act influenced by pathogen stability, immune response strength, and the pathogen’s structure. Diseases like measles and polio demonstrate the effectiveness of stable pathogens in creating lifelong immunity, while the flu serves as a reminder of the challenges posed by mutating viruses.

It was just another day for Zhu (alias name), a 64-year-old construction worker from the eastern Zhejiang province of China. While returning from work, he bought meat for his spicy hot pot broth, a dish enjoyed with fresh meat cuts being cooked in the hot boiling broth and eaten immediately.

It wasn’t until days later that Zhu started experiencing headaches and epilepsy-like symptoms such as limb-twitching, mouth foaming, etc. Witnessing the symptoms, his co-workers encouraged Zhu to get medical help. At the hospital he went through multiple tests and scans which revealed abnormal deposits of calcium in his brain blood vessels. Even though the doctors wanted to explore further, he was reluctant, but he eventually gave in when the symptoms persisted.

An MRI confirmed what the doctors feared. The concerning headaches, twitching-limbs and mouth foaming were all caused by Tapeworms! The tapeworm larvae from the meat cuts had survived because they were not cooked properly.

This 2019 case study done by the First Affiliated Hospital of Zhejiang University is not the only bizarre case of brain parasites. Many people across the world have experienced them; who never thought their generic symptoms were due to an uninvited guest living in their brains. But these brain worms can do a lot more than trigger physical symptoms.

When Change In Behavior Is Not A Surface-Level Problem

To understand the different aspects of brain parasites and how they can affect the human mind, we spoke to Mr. Abhijeet Satani, Neuroscientist and Dr Srikanth, Consultant Neurologist at Apollo Hospitals.

Usually when we feel irritable or forgetful, we chalk it up to stress and lack of sleep. However, have you ever considered the possibility of a parasite living in your brain? Mr. Satani explains that even though it sounds like fiction, neurocysticercosis is a real condition caused by tapeworms that infect the brain.

Dr Srikanth adds to the fact, explaining that these worms can not only alter the behavior but could also be responsible for seizures, cognitive decline, mood changes, or even psychosis in severe cases.

“This typically happens when someone ingests contaminated food or water with microscopic tapeworm eggs, often due to poor hygiene.” said Mr. Satani, “Once the parasite reaches the brain, it forms cysts, disrupting normal function. Symptoms can be complex and varied, including seizures, behavioral changes, mood swings, anxiety, or confusion. Some patients are misdiagnosed with depression or schizophrenia, only to discover later that a parasite is causing brain inflammation.”

How Do "Brain Worms" Get Inside Us?

The most common way people get infected with these brain worms is by accidentally consuming microscopic tapeworm eggs. These eggs are often found in contaminated food or water, typically due to poor hygiene. It might surprise you, unlike what many people believe, but you don't have to eat undercooked pork to get infected.

Dr. Srikanth said, “Surprisingly, even vegetarians can get infected through salads or vegetables handled by someone with poor hand hygiene carrying tapeworm eggs.” This means even people who have been lifelong vegetarians can get this condition if they come into contact with contaminated food or water. It's not about the meat you eat, but what your food has been exposed to.

Least Expected Way of Arrival

However, one of the least expected ways one could get infected is from another person. Mr. Satani explained “If someone is carrying the adult tapeworm in their intestines, they can shed eggs through their feces. And if they don’t wash their hands properly, those microscopic eggs can spread to other people. I've seen cases where someone who doesn’t eat meat, doesn’t travel, and lives a relatively healthy lifestyle ends up with brain cysts simply because they were unknowingly exposed through contact. Something as routine as sharing food, touching a contaminated surface, or even eating in a local restaurant with poor hygiene standards could be enough.”

Once these eggs are ingested, they hatch in the stomach. The larvae then travel through the bloodstream, and can eventually reach the brain, where they form cysts. These cysts then disrupt normal brain function.

How Can Parasites Change Our Behavior?

Some parasites have been shown to change how animals behave, and we're seeing similar patterns in humans. Mr. Satani explained that with "brain worms," changes in behavior usually come from the physical disruption and swelling caused by the cysts in specific parts of the brain.

“I’ll never forget a man in his late 30s who was being treated for what doctors thought was bipolar disorder. He had episodes of paranoia, sudden anger, and intense mood swings. Medications weren’t helping much, and his family was confused and distressed. Eventually, someone suggested getting a brain scan, and to everyone’s surprise, the MRI showed multiple cysts in his brain. He was diagnosed with neurocysticercosis. After proper treatment, including antiparasitic drugs and steroids, his behaviour started to stabilise. He went from being considered a psychiatric patient to someone dealing with a treatable brain infection.”

Dr. Srikanth adds that these changes can range from mood disorders to seizures, depending on where the cyst is located. Mr. Satani gave an example, if a cyst forms in the frontal lobe, which is the part of the brain that controls judgment, making decisions, and your personality, it can lead to sudden anger, impulsive actions, or emotional ups and downs. People might become unusually irritable, withdrawn, or paranoid, and it turns out to be due to pressure or swelling in the brain caused by a parasite. These aren't just mental issues; they are real physical changes. Some common changes observed are:

• Forgetting things
• Trouble focusing
• Anxiety
• Depression
• Hallucinations

How Soon Do Symptoms Appear?

Behavioral changes are usually not immediate. Most people don't even realize they're infected until the cysts start affecting how their brain works explained Mr. Satani. This can take anywhere from a few weeks to several months. At first, symptoms might be so small they're ignored—like being a bit more forgetful, anxious, or moody. But over time, especially if more cysts develop or swelling increases, the symptoms become harder to ignore. In some cases, seizures are the first big sign that something serious is wrong.

Dr. Srikanth added another disturbing detail, “Some brain worms can survive for up to two decades, either remaining active or eventually calcifying and becoming dormant.”

Mr Satani explains that our immune system doesn't always get rid of them on its own. In fact, the swelling caused by our immune system trying to fight them can sometimes do more damage than the cyst itself. That's why medical treatment usually involves both medicine to kill the parasite and steroids to reduce the swelling at the same time.

Awareness and Early Detection

The good news is that neurocysticercosis can be treated if caught early. Medical misdiagnoses are common, especially when the symptoms are misleading. Being aware is key. Dr Srikanth detailed, “I’ve seen a man misdiagnosed with dementia whose scan revealed a "starry-sky" brain full of cysts, and a woman with seizures and muscle swelling later found to have worm cysts in both brain and muscle tissues.”

A big thing that people should understand is that changes in behavior could very easily be a possible signs of brain stress, as well as a neurological problem. Infections, tumors, or certain immune system conditions can all start with small changes in how we act or remember things. Mr. Satani concludes the conversation by explaining how dealing with real-life cases of parasites and how a simple brain infection can cause psychological issues “That experience has stayed with me, because it shows how easily the line between mental health and brain health can be blurred—and how crucial it is to look deeper when something feels off.”

While many people do not consider cancer to be a big cause of concern for young adults However, how many times have we heard of stories of young kids suffering with cancer and young adults who had to put their lives on hold due to unexpected cancer diagnoses? The increase in young adults with cancer is not a mere coincidence; a new study shows that the past decade has seen an increase in the number of early-onset gastrointestinal (GI) cancer cases.

New research published in the British Journal of Surgery shows a really worrying trend, they stated cancers of the stomach, intestines, and other digestive organs are increasing incredibly fast in people 50 and younger in the U.S. This isn't just a small increase; it's happening quicker than any other type of cancer in younger people. It's a big health concern for younger Americans.

Scope of the Problem

The study points out that between 2010 and 2019, the number of GI cancer cases in young people jumped by almost 15%. While colon cancer is the most common of these early cancers, making up over half the cases worldwide, it's not the only one. Cancers of the pancreas, stomach, and esophagus are also becoming more common in younger individuals. This is extra concerning because when younger people get these cancers, they often act more aggressively, meaning they need more intense treatment, and sadly, their chances of survival can be similar to or even worse than older patients.

Who is Most Affected?

While most GI cancer cases are still in people aged 40 to 49, the increase is even steeper in younger age groups. For example, if you were born in 1990, you're twice as likely to get colon cancer and four times as likely to get rectal cancer compared to someone born in 1950. Data from the CDC (Centers for Disease Control and Prevention) confirms this, showing that colon cancer rates have more than tripled in teenagers (15-19) and almost doubled in young adults (20-24). Also, recent studies from 2018 to 2022 found that women saw bigger increases in several early-onset GI cancers:

Colon cancers: Went up by 5% each year for women, compared to 3.5% for men.

Esophageal cancers: Increased almost 6% yearly for women, versus 1% for men.

Stomach cancers: Rose about 4% each year for women, and less than 3% for men.

Small intestine cancers: Grew by 3.5% for women, and under 3% for men.

On top of that, the studies highlighted that Black, Hispanic, and Native American people are being affected much more by this rise in GI cancers.

Critical Need for Screening and Prevention

Despite these alarming numbers, new guidelines that recommend colon cancer screening for healthy people starting at age 45 haven't been widely adopted. In fact, in 2021, only about 1 in 5 Americans aged 45 to 49 actually got screened.

Getting screened is super important! It's been proven to save lives by not only reducing the number of people who get colorectal cancer but also by lowering the number of deaths from it. Every time someone skips a screening, it's a lost chance to find cancer early when it's easier to treat, or even to prevent cancer entirely by finding and removing precancerous growths called polyps.

Risk Factors and Future Directions

Several things can increase your risk of getting GI cancer, including being overweight, eating a lot of high-fat Western-style foods, having fatty liver disease, smoking, and drinking alcohol.

Researchers are now urging more studies to figure out why GI cancer rates are going up in younger adults. They're also pushing for better ways to prevent these cancers and find them early. More information is especially needed for pancreatic, stomach, and esophageal cancers. Raising awareness and educating people about these issues is vital because, as a group, digestive system cancers cause a significant number of cancer-related deaths in young adults both in the U.S. and around the world.

Every year, World Brain Day is marked to raise awareness around brain health and neurological conditions that often go undiagnosed or misunderstood. This year’s theme focuses on brain health and early detection, emphasizing how subtle signs—often brushed off as routine stress—may actually be the brain’s way of raising an alarm.

While stress-related fatigue, burnout, and tension headaches are all-too-common in today’s never-resting, always hustling world, experts warn that dismissing persistent or unusual neurological symptoms as “just stress” could delay diagnosis of something more serious, such as a brain tumor.

We spoke with Dr. Mukesh Kumar, Director and Head (Parkinson's Disease Unit), Neurosciences, Neurology, Max Super Speciality Hospital, Saket, to understand the difference between stress symptoms and potential red flags.

Not All Headaches Are Just “Stress Headaches”

Headaches are the most common symptom people link with stress, but not all headaches are created equal.

Dr. Kumar explains, “A worst headache in the morning may be a feature of subarachnoid haemorrhage (SAH), which is a medical emergency. Stress headaches are usually mild to moderate and without vomiting. SAH is usually very severe and comes with nausea or vomiting.”

He adds that if your headache feels significantly different from your usual ones, especially if it’s persistent, worsening over time, or most intense after waking up, it’s worth seeking a neurological opinion.

Brain Fog vs. Brain Tumor-Linked Cognitive Symptoms

Feeling mentally scattered, struggling to focus, or forgetting things easily? It could be burnout, but not always.

“Brain fog due to burnout is usually transient, affecting multiple domains and without any functional disability,” says Dr. Kumar. It’s often tied to sleep issues like delayed sleep initiation or fragmented rest.

On the other hand, “Cognitive disability related to a brain tumor may affect one or more specific cognitive domains, tends to persist, and comes with functional disability,” he adds. You may also notice seizures, limb weakness, or trouble with routine tasks.

Clumsiness and Loss of Balance: When It’s Not Just Fatigue

Occasional clumsiness may seem harmless, especially during hectic workweeks. However, if it progresses to frequent falls, a noticeable decline in coordination, or needing support for routine tasks, don’t ignore it.

Dr. Kumar advises, “See a neurologist if there’s physical disability, frequent falls, need for support in walking, or significant reduction in your day-to-day functional efficiency.”

These may point to disturbances in the brain’s motor control centers, possibly caused by a tumor affecting balance and coordination.

Sudden Mood Swings or Personality Changes? Take Note

Stress does affect mood, but a rapid and unexplained shift in personality could be neurological. “Sudden personality changes, if persistent for a few days to weeks, suggest early features of a brain tumor,” says Dr. Kumar.

So, if someone who’s usually calm becomes irritable, withdrawn, or impulsive with no clear reason—and these changes don’t go away, it’s time for a deeper evaluation.

Vision and Speech Fluctuations

Blurred vision, slurred speech, or trouble finding the right words after a long day might seem like signs of tiredness. But if these symptoms come and go—or worsen—don’t brush them off.

According to Dr. Kumar, watch out for “faster reaction or impulsive behaviour, neck and back pain, early morning back stiffness, fluctuating vision or speech issues, and disturbed sleep patterns.” These are neurological red flags that demand attention.

Listen to Your Brain

The key message this World Brain Day is simple: Don’t ignore what your brain is trying to tell you. While stress is real and widespread, persistent or unusual symptoms—especially if they’re affecting your daily life—deserve a professional checkup.

As Dr. Kumar sums it up, “Early detection can significantly improve outcomes in brain tumors. When in doubt, get it checked out.”