Host (biology)
In
biology, a
host is an organism that harbors a
virus,
parasite, mutual partner, or commensal partner, typically providing nourishment and shelter.
Examples: A
cell can be host to a
virus, a
legume plant can be host to helpful
nitrogen-fixing bacteria, an
animal can be host to a parasitic
worm, e.g. a
nematode.
A
primary host or
definitive host is a host in which the parasite grows mature; a
secondary host or
intermediate host is a host that harbors the parasite only for a short transition period. For
trypanosomes, the cause of
sleeping sickness,
humans are the primary host, while the
tsetse fly is the secondary host.
The
host range or
host specificity of a parasite is the collection of hosts that an organism can utilize as a partner. In the case of human parasites, the host range influences the epidemiology of the parasitism or disease. For instance, the production of
antigenic shifts in
Influenza A virus can result from pigs being infected with the virus from several different hosts (such as human and bird). This co-infection provides an opportunity for mixing of the viral genes between existing strains, thereby producing a new viral strain. An
influenza vaccine produced against an existing
viral strain might not be effective against this new strain, which then requires a new influenza vaccine to be prepared for the protection of the human population.
There are also
reservoir hosts. These are vertebrates that host an infection while it isn't infecting humans and is used by the disease as a source of maintenance. A single reservoir host may be reinfected several times.
*
Symbiosis*
Vector*
Intermediate hostCenters for Disease Control and Prevention (2004).
The Influenza (Flu) Viruses:Transmission of Influenza Viruses from Animals to People. Retrieved 2005-02-26.
