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Flu virus surge in cities: Can you get it twice in one season?

While complete protection against viruses is difficult, preventive hygiene is key

viral, multiple viral fever, health and wellness

Understanding the causes of repeated viral infections and how to protect your immune system.

If you have fallen sick multiple times from what seems like the same virus in a single season, you are not alone. Many people experience repeated bouts of illness even after recovering once. While it may seem like the virus never left your system, several biological and environmental factors contribute to this phenomenon. Here’s why this happens and what you can do about it.

Variants and Mutations: Viruses, especially respiratory ones like the flu or COVID-19, evolve quickly. When you catch a virus, your immune system builds antibodies specific to that strain. However, if the virus mutates slightly, your body may not recognize it as the same infection. This means you can fall sick multiple times, even if you have developed immunity to an earlier version. For example, the influenza virus has multiple strains, and each season may bring slightly different versions. COVID-19, which has shown numerous mutations, led to reinfections in people who had been vaccinated or previously infected.

Weak or Short-Lived Immunity: Not all immune responses provide long-term protection. Some viruses only trigger temporary immunity, which can wane within weeks or months. If your body doesn’t build a strong enough defence, you might become vulnerable to reinfection sooner than expected. Additionally stress, poor diet, lack of sleep and underlying health conditions can weaken your immune system.

Reactivation of Dormant Viruses: Certain viruses, such as Epstein-Barr virus (EBV) and herpesviruses, can remain dormant in the body and reactivate when immunity is weakened. While most respiratory viruses do not behave this way, lingering symptoms or secondary infections might make it look like you are getting sick repeatedly. For example, after COVID-19, your immune system remains suppressed for a while, increasing the risk of catching another illness or experiencing prolonged symptoms.

Overlapping Illnesses: Sometimes, getting sick again does not mean you caught the same virus—it could be a different one altogether. Many viruses circulate simultaneously during peak seasons, and you may get infected by another pathogen while your immune system is still recovering from the first one. For instance, a person recovering from a cold (caused by rhinoviruses) may soon get the flu (caused by influenza), leading to the perception of repeated sickness from the same virus.

Environmental Exposure: If you are frequently exposed to sick people — whether at work, school or public places — you increase your chances of reinfection. Viruses can linger on surfaces, in the air and in crowded spaces. Moreover, some viruses, such as norovirus and adenoviruses, can remain on surfaces for days, making reinfection more likely if proper sanitization isn’t practised.

Post-Viral Syndrome: Another possibility is that you are not experiencing new infections but rather lingering symptoms from the initial illness. Some people develop post-viral syndromes where fatigue, cough, congestion and weakness persist for weeks. This can give the impression of multiple infections when, in reality, the body is still recovering from the original virus, long Covid being an example.

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While complete protection against viruses is difficult, you can take several steps to minimise your risk: Eat a balanced diet, stay hydrated, get enough sleep and manage stress. Practise hygiene and mask up in crowded areas. Finally, do not rush back to activities before fully recovering, it can weaken your immune system further.

(Dr Chatterjee is internal medicine specialist, Apollo Hospitals, Delhi)