What is flu?

Influenza A is one of the most common life-threatening viruses in the United States each year infecting approximately 10% of the u.s. population and causing about 20,000 deaths influenza is normally transmitted by droplets or aerosols from the sneeze or cough of a nearby infected person when another individual inhales the droplets the virus has a chance to invade the cells of a new host influenza a can a genome of single-stranded RNA segments enzymes required for viral replication inside a host cell and a shell of matrix proteins.

The virus also has a phospholipid envelope with several embedded proteins including a molecule called hemagglutinin shortened H a or H which plays an essential role in viral cell access virus binds to host cell receptor proteins that contain polysaccharides terminating with sciatic acid a psionic acid that is attached to galactose furnishes a recognition site for the viruses hemagglutinin protein the sialic acid can be attached at various roles on galactose this example shows an alpha 2 3 associations between the digit 2 carbon of cyanic acid and the number 3 carbon of galactose.

The avian influenza strain h5n1 recognizes primarily this alpha to three linked version of the carbohydrate which is established in birds in humans such carbohydrates are based only deep within the lungs which may explain why the h5n1 strain though deadly is infrequently transmitted between humans in distinction the upper respiratory parcel of humans contains mainly alpha to six linked receptors and is to these receptors that human influenza A viruses bond.

The hemagglutinin complex consists of a trimer of subunits each subunit comprises a domain that passes through the viral envelope and a profession that binds to the cyanic acid receptors on the announcer cell for translucency let's look at simply one of these three subunits for an influenza virus to evolve infective hemagglutinin must be cleaved an enzyme discharged from the epithelial lining of the human respiratory tract performs this procedure. The separation frees one end of a component called a fusion peptide the fusion peptide is hydrophobic and buried within the core of the hemagglutinin trimeric complex.

The host cell takes up the virus by endocytosis the endo side vesicle then fuses with a lysosome and its interior acidifies the lowered pH persuades a conformational modification motion the receptor binding region back and triggers the fusion peptides forward to infiltrate the vesicle membrane several trimeric hemagglutinin molecules in the identical area of the membrane mediate fusion between the viral and keeper membranes the fusion method expels the scopes of the virus into the host cytoplasm the virus is ready to begin its reduplication process.