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This causes an immune response, resulting in common symptoms as phagocytes break down the bacteria within the host. Some bacteria, such as H. pylori, can secrete toxins into the surrounding tissues, resulting in cell death or inhibition of normal tissue function. Viruses, however, use a completely different mechanism to cause disease.
Host cell invasion and replication by the influenza virus. The viral life cycle begins by binding to a target cell. Binding is mediated by the viral HA proteins on the surface of the envelope, which bind to cells that contain sialic acid receptors on the surface of the cell membrane.
Under disease invasion, when a parasite invades a new host species, it may become pathogenic in the new host. [ 106 ] Several human activities have led to the emergence of zoonotic human pathogens, including viruses, bacteria, protozoa, and rickettsia, [ 107 ] and spread of vector-borne diseases, [ 106 ] see also globalization and disease and ...
Unlike viruses, bacteria can replicate and divide on their own without entry into a host cell. Still, to grow and divide, bacteria require certain nutrients from their environment. These nutrients can often be provided by host tissues, and that is why some bacteria need a host for survival. Once a bacterium recognizes the host cell receptors or ...
Tissue tropism is the range of cells and tissues of a host that support growth of a particular pathogen, such as a virus, bacterium or parasite. [1] [2] Some bacteria and viruses have a broad tissue tropism and can infect many types of cells and tissues. [1] Other viruses may infect primarily a single tissue. [1]
Influenza viruses: You’re likely familiar with the seasonal flu, but in the last century there have also been four influenza pandemics: the infamous Spanish Flu pandemic in 1918, the H2N2 flu ...
As before, the viruses then adhere to the same host cell capsule through hemagglutinin; the mature viruses detach once their neuraminidase has cleaved sialic acid residues from the host cell. [16] After the release of new influenza virus, the host cell dies, and infection repeats in other host cells.
Some bacteria, such as Streptococcus pyogenes, Staphylococcus aureus and Pseudomonas aeruginosa, produce a variety of enzymes which cause damage to host tissues.Enzymes include hyaluronidase, which breaks down the connective tissue component hyaluronic acid; a range of proteases and lipases; DNases, which break down DNA, and hemolysins which break down a variety of host cells, including red ...