Influenza

**Influenza**, dem commonly know as de **flu**, be an infectious disease wey be caused by influenza viruses. Symptoms dey range from mild to severe den often include fever, runny nose, sore throat, muscle pain, headache, coughing, den fatigue. Dese symptoms dey begin one to four (typically two) days after exposure to de virus den last for about two to eight days. Diarrhea den vomiting fi occur, particularly insyd kiddies. Influenza fi progress to pneumonia from de virus anaa a subsequent bacterial infection. Oda complications dey include acute respiratory distress syndrome, meningitis, encephalitis, den worsening of pre-existing health problems such as asthma den cardiovascular disease. 

Der be four types of influenza virus: types A, B, C, den D. Aquatic birds be de primary source of influenza A virus (IAV), wich sanso widespread insyd various mammals, wey dey include humans den pigs. Influenza B virus (IBV) den influenza C virus (ICV) primarily dey infect humans, wey dem dey find influenza D virus (IDV) insyd cattle den pigs. Influenza A virus den influenza B virus circulate insyd humans den cause seasonal epidemics, den influenza C virus dey cause a mild infection, primarily insyd kiddies. Influenza D virus fi infect humans buh e no be known to cause illness. Insyd humans, influenza viruses primarily be transmitted thru respiratory droplets from coughing den sneezing. Transmission thru aerosols den surfaces be contaminated by de virus sanso occur. 

Frequent hand washing den covering one ein mouth den nose wen coughing den sneezing reduce transmission, as do wearing a mask. Annual vaccination fi help to provide protection against influenza. Influenza viruses, particularly influenza A virus, dey evolve quickly, so flu vaccines be updated regularly to match wich influenza strains be insyd circulation. Vaccines dey provide protection against influenza A virus subtypes H1N1 den H3N2 den one anaa two influenza B virus subtypes. Influenza infection be diagnosed plus laboratory methods such as antibody anaa antigen tests den a polymerase chain reaction (PCR) to identify viral nucleic acid. De disease fi be treated plus supportive measures den, insyd severe cases, plus antiviral drugs such as oseltamivir. Insyd healthy individuals, influenza typically be self-limiting den rarely fatal, buh e fi be deadly insyd high-risk groups. 

Insyd a typical year, five to 15 percent of de population dey contract influenza. Der be 3 to 5 million severe cases annually, plus up to 650,000 respiratory-related deaths globally each year. Deaths most commonly dey occur insyd high-risk groups, wey dey include young kiddies, de elderly, den people plus chronic health conditions. Insyd temperate regions, de number of influenza cases dey peak during winter, whereas insyd de tropics, influenza fi occur year-round. Since de late 1800s, na pandemic outbreaks of novel influenza strains occur every 10 to 50 years. Na five flu pandemics occur since 1900: de Spanish flu from 1918 to 1920, wich na be de most severe; de Asian flu insyd 1957; de Hong Kong flu insyd 1968; de Russian flu insyd 1977; den de swine flu pandemic insyd 2009. 

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