Flu

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Obesity, Sleep & Internal medicine
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Influenza Nomenclature Diagram

Influenza, often referred to as the flu, is an infectious disease that primarily affects birds and mammals, specifically targeting the upper airways and lungs in mammals. The disease is a result of the RNA virus that belongs to the Orthomyxoviridae family, more specifically, the influenza viruses. In humans, the most common symptoms of influenza include fever, pharyngitis, myalgia, severe headache, cough, and malaise.

It's crucial to differentiate between the flu and other conditions such as the common cold or 'stomach flu'. The latter are not associated with the influenza virus. The term 'stomach flu', or "24 hour flu", often refers to Gastroenteritis, but it's a misnomer since it's unrelated to the actual flu.

Epidemic outbreaks of flu occur seasonally and can result in widespread death, especially during pandemic years. Non-pandemic years still witness hundreds of thousands of deaths. Besides the mortality, influenza also imposes significant health care costs and hampers productivity. Notably, in the 20^th century, three major influenza pandemics, due to significant genetic shifts in the virus, resulted in the deaths of millions globally. Currently, H5N1 poses the most significant threat as an influenza pandemic, although it predominantly affects birds.

Historically, the term 'influenza' was first coined in 15th century Italy, attributed to negative astrological influences. Over time, as medical knowledge evolved, the term was modified to "influenza di freddo", which means "influence of the cold". This terminology gained popularity in the English-speaking world by the 18th century.

Etymology

The Modern English term "influenza" came into use in 1743 during a European disease outbreak. It was borrowed from the Italian term "influenza", originally signifying "influence", referencing the once-held belief that the disease was a result of the stars' influence.

History

Hippocrates provided an early description of influenza symptoms in 412 B.C. Over the centuries, the virus underwent numerous mutations and shifts, leading to several pandemics. The first recorded influenza pandemic appeared in 1580. Since then, various methods have been explored to combat the disease.

Notable outbreaks often result from antigenic shift, a process wherein two influenza strains merge, forming a deadly new strain. A significant outbreak, known as the Spanish Flu pandemic (type A influenza, H1N1 strain), persisted from 1918 to 1919, causing more deaths than World War I. While war casualties spread over years, the pandemic caused most of its devastation within weeks. Other flu epidemics include the 1957 Asian Flu (type A, H2N2 strain) and the 1968 Hong Kong Flu (type A, H3N2 strain).

Known flu pandemics

• 1889-90 - Asiatic (Russian) Flu, mortality rate approximated at 0.75-1 death per 1000, possibly H2N2
• 1900 - possibly H3N8
• 1918–20 – Spanish Flu, with 500 million afflicted and over 40 million fatalities due to H1N1
• 1957–58 – Asian Flu, causing 1 to 1.5 million deaths from H2N2
• 1968–69 – Hong Kong Flu, resulting in 3/4 to 1 million deaths from H3N2

Negatively stained flu virions, the causative agent of the Hong Kong Flu pandemic.

Although significant scares appeared in New Jersey in 1976 (Swine Flu), globally in 1977 (the Russian Flu), and in Asian countries including Hong Kong in 1997 (Avian influenza), no major pandemics have emerged since the 1968 episode. Increased immunity via antibody response has potentially limited the flu's spread in these instances.

Prevention and Treatment

Main article: influenza vaccine

The influenza vaccine offers the best prevention strategy. The vaccine composition changes annually, based on prevalent flu strains. These vaccines generally protect against three to four influenza strains.

Antiviral drugs, including oseltamivir and zanamivir, offer treatment post-infection and also serve as a preventive measure during outbreaks. Timely administration, ideally within 48 hours of symptom onset, enhances their effectiveness.

See Also

• Common cold
• Pneumonia
• Avian influenza
• Swine influenza
• COVID-19 pandemic

External Links

• WHO Influenza (Flu) Official Page
• CDC Influenza (Flu) Main Page
• U.S. Government Flu Information

Flu Resources
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