Influenza virus infection is a highly contagious airborne disease. It causes acute febrile respiratory illness and results in varying degrees of systemic symptoms, ranging from mild fatigue to respiratory failure and even death. It is responsible for infecting 5–15% of the global population annually. Influenza is a viral infection and commonly called the flu.
Family: Orthomyxoviridae
Types: A, B, and C
Influenza B and C viruses have a very limited host range and are mainly present in humans whereas influenza A reservoirs are human as well as wild aquatic birds and other animal species like birds, pigs, ferrets, horses, seals, whales, mink, giant anteaters, cats, and dogs.
Influenza virus was the causative agent of following-
“Spanish” flu in 1918–1919
“Asian” flu in 1957–1958 (H2N2 subtype
“Hong Kong” flu in 1968–1969 (H3N2 subtype)
1957 pandemic was caused by the H3N2 influenza virus and originated in China
2009 Pandemic H1N1, the virus of swine-origin emerged in Mexico and the USA in early April 2009.
Transmission: Infection due to inhaling the viruses through droplet infection.
Incubation period: 1–5 days
Following groups are more prone to infection-
Common signs and symptoms
Emergency signs and symptoms may include:
For the demonstration of the Virus:
Culture: Egg inoculation, tissues culture, and monkey kidney cell lines.
Molecular Test: Reverse transcriptase-polymerase chain reaction (RT-PCR)
Two classes of antiviral compounds approved by the US FDA are Adamantane group drugs (amantadine and rimantadine) that block the activity of the viral M2 proton channel, preventing the virus from uncoating and inhibiting the release of the viral genome into host cells, while the second group of dugs is NA inhibitors (Oseltamivir/Tamiflu and zanamivir/Relenza) that bind and block enzymatic activity.
The vaccine is available. Influenza vaccine is not 100% effective, so it is also important to take a number of measures to reduce the spread of infection, including:
PB1: Polymerase basic protein 1
PA: Polymerase acidic protein (PA)
HA: Haemagglutinin
NA: Neuraminidase
NP: Nucleoproteins
M1: Matrix protein 1
NS1: non-structural proteins 1
SO-IVA: Swine origin influenza virus A
vRNP: Viral ribonucleoprotein particles