Influenza (seasonal): Acute respiratory infection caused by influenza viruses
Seasonal influenza: Acute respiratory infection circulating worldwide
Margaret Anderson (Chicago, USA) thought she just had a bad cold. She was 72, generally healthy, lived independently, and prided herself on rarely getting sick. When she developed fever, cough, and body aches in January 2023, she dismissed it as “just the flu” and stayed home, taking over-the-counter cold medicine and waiting to recover.
“Everyone gets the flu. It’s no big deal. You rest, drink fluids, take some medicine, and you’re better in a few days. That’s what I thought,” Margaret recalled from her hospital bed, her voice weak, oxygen tubes in her nose.
But Margaret’s symptoms worsened. Her fever spiked to 103°F. Her cough became severe and painful. She couldn’t catch her breath. Her daughter, visiting on day three, found her confused and struggling to breathe. She called an ambulance immediately.
At the emergency room, tests confirmed Margaret had influenza. But the virus had triggered bacterial pneumonia. Her lungs were failing. She was admitted to intensive care, placed on high-flow oxygen, given intravenous antibiotics and antiviral medications. For five days, her survival was uncertain.
“The doctors told my daughter I might not make it. They said if I’d been treated with antivirals in the first 48 hours—when my symptoms started—I probably wouldn’t have developed pneumonia. But I waited too long. I didn’t realize that flu can be deadly, especially for elderly people like me. I thought flu was just an inconvenience. I was wrong. It nearly killed me,” Margaret explained.
Margaret also learned something else that shocked her: she’d never received a flu vaccine. “My doctor recommended it every year. I always refused. I didn’t believe in vaccines. I thought my immune system was strong enough. I thought flu vaccines were unnecessary, maybe even harmful. Those beliefs almost cost me my life.”
According to WHO, Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world. It represents a year-round disease burden. It causes illnesses that range in severity and sometimes lead to hospitalization and death. Most people recover from fever and other symptoms within a week without requiring medical attention. However, influenza can cause severe illness or death, particularly among high risk groups including the very young, the elderly, pregnant women, health workers and those with serious medical conditions.
For more on respiratory diseases, see our articles on infectious diseases and vaccine-preventable illnesses at ObserverVoice.com.
Global Patterns and Symptoms
In temperate climates, seasonal epidemics occur mainly during winter, while in tropical regions, influenza may occur throughout the year, causing outbreaks more irregularly. Seasonal influenza is characterized by a sudden onset of fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and a runny nose. The cough can be severe and can last two or more weeks.
For patients that are not in a high risk group, treatment focuses on relieving symptoms of influenza such as fever. Patients that are known to be in a group at high risk for developing severe or complicated illness should seek medical attention and should be treated with antiviral drug as soon as possible.
WHO provides Influenza (seasonal) fact sheet and How can I avoid getting the flu? Q&A. WHO provides Influenza update and country profiles, FluNet tool, and Surveillance situation reports.
Related topics include Influenza (avian and other zoonotic). For more on prevention, see our article on vaccination programs at ObserverVoice.com.
WHO Surveillance and Vaccine Development
WHO’s Global Influenza Programme (GIP) coordinates global efforts. WHO established Global Influenza Surveillance and Response System (GISRS) monitoring influenza viruses worldwide. WHO implements Pandemic Influenza Preparedness Framework (PIP) for preparedness. World Health Assembly passed WHA64.5 on Pandemic influenza preparedness: sharing of influenza viruses and access to vaccines.
September 2025 WHO announced Recommendations for influenza vaccine composition for 2026 southern hemisphere season. March 2025 WHO reported Expanding Global Influenza Surveillance and Response System to include other respiratory viruses. March 2025 WHO reported Despite global influenza vaccine production remaining steady, challenges remain. March 2025 WHO reported Influenza surveillance in conflict-affected areas of Myanmar.
Recent Publications and Guidelines
January 2026 WHO published Improved influenza vaccines: full value vaccine assessment noting seasonal influenza remains major global public health challenge. December 2025 WHO published WHO guidance on use of licensed human influenza A(H5) vaccines for interpandemic and emergence periods outlining primary objectives. December 2025 WHO published WHO preferred product characteristics for next generation influenza vaccines, second edition to guide development. September 2025 WHO published Public health resource pack for countries experiencing outbreaks of influenza in animals.
December 2025 WHO featured Republic of Congo strengthens pandemic preparedness with influenza sentinel surveillance. December 2025 WHO featured South-East Asia Region on course for stronger pandemic preparedness. December 2025 WHO featured Uzbekistan’s virology laboratory achieves ISO accreditation. December 2025 WHO featured Ethiopia achieves WHO Maturity Level 3 in medicines regulation.
WHO provides infographics showing Protecting yourself from influenza, Influenza high risk groups, Vaccination protects you, and Vaccination protects health workers. WHO campaigns include Influenza: are we ready? spotlight, History of influenza vaccination, and World Immunization Week (April 24-30).
Prevention Through Vaccination and Awareness
Margaret survived her influenza infection and pneumonia. After three weeks in hospital and months of recovery, she returned to independent living. But she returned transformed—no longer skeptical about vaccines, no longer dismissive of flu as “just a cold.”
“The day I was discharged from hospital, I asked my doctor: ‘When can I get the flu vaccine?’ He smiled and said, ‘As soon as you’re fully recovered—in about six weeks.’ I got vaccinated as soon as I was eligible. I’ve gotten my annual flu shot every year since. I’m now 75, and I haven’t had flu again,” Margaret explained.
“I also became a vaccine advocate—especially among elderly people who, like me, didn’t take flu seriously. I share my story at senior centers, community groups, church gatherings. I explain that seasonal influenza isn’t just a bad cold—it’s a serious disease that kills hundreds of thousands of people globally every year. I emphasize that elderly people, young children, pregnant women, people with chronic conditions, and healthcare workers are at highest risk for severe illness and death,” Margaret continued.
“I explain that flu vaccination is safe, effective, and saves lives. WHO recommends annual vaccination for high-risk groups. The vaccine is updated every year because influenza viruses constantly evolve. WHO’s Global Influenza Surveillance and Response System monitors circulating strains worldwide and recommends which strains to include in seasonal vaccines. This global surveillance ensures vaccines target the viruses most likely to cause illness each season,” Margaret emphasized.
“I also teach people to recognize warning signs requiring immediate medical care: difficulty breathing, chest pain, confusion, severe weakness, high fever lasting more than three days. I stress that antiviral medications work best when started within 48 hours of symptom onset—early treatment can prevent complications like the pneumonia that nearly killed me. Most people recover from flu at home within a week, but high-risk individuals should see a doctor immediately,” Margaret noted.
“WHO’s work on seasonal influenza surveillance, vaccine development, and public health guidance saves millions of lives annually. WHO coordinates global monitoring of circulating strains, facilitates international sharing of virus samples and data, updates vaccine recommendations twice yearly for northern and southern hemispheres, supports countries in strengthening influenza surveillance and response capacity, and promotes vaccination of high-risk populations. My survival reminds me daily: flu is preventable. Vaccination works. Early treatment matters. WHO’s leadership on influenza is protecting global health—one vaccine, one surveillance report, one life saved at a time.”
For more information, visit WHO’s influenza (seasonal) topic page or explore related content at ObserverVoice.com.
Frequently Asked Questions (FAQs)
Seasonal influenza is acute respiratory infection caused by influenza viruses which circulate in all parts of world. It represents year-round disease burden. It causes illnesses that range in severity and sometimes lead to hospitalization and death. Most people recover from fever and other symptoms within week without requiring medical attention. However, influenza can cause severe illness or death, particularly among high risk groups including very young, elderly, pregnant women, health workers and those with serious medical conditions. In temperate climates, seasonal epidemics occur mainly during winter, while in tropical regions, influenza may occur throughout year. Seasonal influenza is characterized by sudden onset of fever, cough (usually dry), headache, muscle and joint pain, severe malaise, sore throat and runny nose. Cough can be severe and can last two or more weeks. WHO provides Influenza fact sheet and How can I avoid getting flu? Q&A. Related: Influenza (avian and other zoonotic).
For patients that are not in high risk group, treatment focuses on relieving symptoms of influenza such as fever. Patients that are known to be in group at high risk for developing severe or complicated illness should seek medical attention and should be treated with antiviral drug as soon as possible. High risk groups include very young, elderly, pregnant women, health workers and those with serious medical conditions. January 2026 WHO published Improved influenza vaccines: full value assessment. December 2025 WHO published WHO guidance on use of licensed human influenza A(H5) vaccines. December 2025 WHO published Preferred product characteristics for next generation vaccines, second edition. WHO’s Global Influenza Programme coordinates efforts. WHO provides Influenza update and country profiles and FluNet tool. Related: Influenza (avian and other zoonotic).
WHO’s Global Influenza Programme (GIP) coordinates global efforts. WHO established Global Influenza Surveillance and Response System (GISRS) monitoring influenza viruses worldwide. WHO implements Pandemic Influenza Preparedness Framework (PIP) for preparedness. WHO provides Surveillance situation reports. September 2025 WHO announced Recommendations for vaccine composition for 2026 southern hemisphere. March 2025 WHO reported Expanding GISRS to include other respiratory viruses. March 2025 WHO reported Influenza surveillance in conflict-affected Myanmar. December 2025 WHO featured Congo strengthens pandemic preparedness. Related: Influenza (avian and other zoonotic).
January 2026 WHO published Improved influenza vaccines: full value vaccine assessment noting seasonal influenza remains major global public health challenge. December 2025 WHO published WHO guidance on use of licensed human influenza A(H5) vaccines for interpandemic periods. December 2025 WHO published WHO preferred product characteristics for next generation influenza vaccines, second edition. September 2025 WHO published Public health resource pack for countries experiencing outbreaks of influenza in animals. March 2025 WHO reported Despite vaccine production remaining steady, challenges remain. December 2025 WHO featured South-East Asia Region preparedness. December 2025 WHO featured Uzbekistan laboratory ISO accreditation. World Health Assembly passed WHA64.5 on Pandemic influenza preparedness. Related: Influenza (avian and other zoonotic).
WHO provides How can I avoid getting flu? Q&A with guidance. Annual vaccination recommended for high-risk groups including very young, elderly, pregnant women, health workers and those with serious medical conditions. WHO coordinates World Immunization Week (April 24-30) promoting vaccination. WHO provides infographics on Protecting yourself from influenza, Influenza high risk groups, Vaccination protects you, and Vaccination protects health workers. WHO campaigns include Influenza: are we ready? spotlight and History of influenza vaccination. December 2025 WHO featured Ethiopia achieves WHO Maturity Level 3 in medicines regulation. WHO’s Global Influenza Programme coordinates efforts. WHO provides Influenza fact sheet. Related: Influenza (avian and other zoonotic).
- WHO Influenza (Seasonal) Topic Page
- WHO Global Influenza Surveillance and Response System
- WHO Global Influenza Programme
- WHO FluNet Tool
- WHO Pandemic Influenza Preparedness Framework
Disclaimer: This article is an adaptation of publicly available information from WHO’s Influenza (seasonal)
health topic page (WHO, Geneva. Licence: CC BYNC-SA 3.0 IGO). WHO is not responsible for the
content or accuracy of this adaptation. This content is for informational and educational purposes
only and does not constitute medical advice. ObserverVoice.com is a news and information platform
— not a healthcare provider.
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