What is the difference between flu and a cold?

Flu symptoms come on suddenly and are more severe than a cold. Flu typically causes high fever (100-104°F), body aches, extreme fatigue, and dry cough. Colds develop gradually with milder symptoms like runny nose, sneezing, and sore throat. Flu is also more likely to cause serious complications requiring hospitalization.

How does the flu spread?

Flu spreads primarily through respiratory droplets when infected people cough, sneeze, or talk. You can also get flu by touching contaminated surfaces and then touching your face. People with flu are most contagious in the first 3-4 days after illness begins, but can spread the virus 1 day before symptoms start.

How effective is the flu vaccine?

Flu vaccine effectiveness varies by season (typically 40-60% effective) based on how well the vaccine matches circulating strains. Even when not perfectly matched, the vaccine reduces illness severity, hospitalizations by 40-60%, and deaths. It takes about 2 weeks after vaccination for antibodies to develop.

What are flu complications to watch for?

Serious complications include pneumonia, bronchitis, sinus infections, ear infections, myocarditis (heart inflammation), and encephalitis (brain inflammation). Warning signs requiring immediate care: difficulty breathing, chest pain, persistent vomiting, confusion, severe weakness, fever returning after improvement, or worsening of chronic conditions.

When should I take antiviral medications?

Antiviral medications (oseltamivir/Tamiflu, zanamivir/Relenza) work best when started within 48 hours of symptom onset. They're recommended for people at high risk of complications, those with severe illness, or hospitalized patients. Antivirals can shorten illness duration by 1-2 days and reduce complications.

Where is flu activity highest right now?

Flu season typically peaks between December and February in the Northern Hemisphere, but can occur year-round in some regions. Check the live outbreak data above for current flu activity levels, dominant strains, and geographic hotspots.

Influenza

1 Active Outbreak

Influenza (flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness and can lead to hospitalization or death, particularly in high-risk populations.

Countries Affected

Recent Cases (30d)

Active Outbreaks

331d ago

Last Updated

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What is Influenza?

Influenza is a seasonal respiratory virus that affects millions of people worldwide each year. Unlike the common cold, flu comes on suddenly and can cause serious complications like pneumonia, especially in children, elderly, pregnant women, and those with chronic conditions. Annual flu vaccination is the best prevention method.

Symptoms

Sudden onset of high fever (100-104°F)
Dry cough
Severe body aches and muscle pain
Extreme fatigue and weakness
Headache
Sore throat
Runny or stuffy nose
Sometimes nausea, vomiting, diarrhea (more common in children)

Transmission

Flu spreads through respiratory droplets when infected people cough, sneeze, or talk. It can also spread by touching contaminated surfaces and then touching the mouth, nose, or eyes. The virus can survive on surfaces for 24-48 hours.

Contagious Period: 1 day before symptoms appear through 5-7 days after becoming sick (children and immunocompromised may be contagious longer)

Prevention

Annual flu vaccination (recommended for everyone 6 months and older)
Frequent handwashing with soap and water for 20 seconds
Avoid touching face (eyes, nose, mouth)
Stay home when sick (at least 24 hours after fever resolves)
Cover coughs and sneezes with tissue or elbow
Clean and disinfect frequently touched surfaces
Avoid close contact with sick people
Consider wearing a mask in crowded indoor settings during flu season

Live Influenza Global Case Map

1 country with reported activity. Updated from real-time surveillance data.

No reports

Low activity

High activity

Active Outbreaks & Recent Cases

Real-time intelligence from global health monitoring and AI-powered surveillance

Data sources: BEACON, ProMED, WHO, CDC, and 50+ national health agencies

✓ Live data updated in real-time from global health sources

None

Zambia, Lusaka Province 2025-08-21

Active

CIDRZ, ZNPHI conducts Panel Discussion on Zambia’s One Health Baseline Study. CIDRZ recently hosted a panel of experts to discuss key findings from the One Health Baseline Study.

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Expert Resources & References

Trusted information from leading health organizations

CDC

Official guidance from the U.S. Centers for Disease Control and Prevention

View CDC Resources →

WHO

Global disease surveillance and guidelines from the World Health Organization

View WHO Resources →

Research

Latest peer-reviewed research and clinical studies

View Research →

Medically Reviewed Content

Disease information on Virus Watcher is reviewed by our Chief Epidemiologist, a former CDC lead analyst for FluSight forecasting. Outbreak data is aggregated from verified sources including BEACON, ProMED, WHO, CDC, and 50+ national health agencies. This information is for educational purposes and should not replace professional medical advice.

Last reviewed: 2026-07-18

Frequently Asked Questions

Common questions about Influenza answered by our epidemiology team

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