### agent | virus:

Enveloped virus
* Most enveloped viruses appear to be spherical, although the rhabdoviruses are elongated cylinders.
* Some enveloped viruses accumulate inside the cell and destroy the cell to facilitate release
  - display special molecules called spikes on their surface
  - have spikes, which are viral glycoproteins that project from the envelope
* acquire the lipid membrane as the virus buds out through the cell membrane
  - their lipoprotein coat by budding through one of the cellular membranes
* are less able to survive in the environment
  - usually spherical because the envelope, unlike the capsid, is loose-fitting
* can easily incorporate cellular proteins and other macromolecules during budding.
* enter cells by fusion of viral and cellular membranes.
* have lipids, therefore are susceptible to chloroform, ether, and other solvents
  - one or more lipoprotein layers surrounding the nucleocapsid
* make their own membranes.
* pick up the host membrane when they leave.

Few virus
* contain more than one component.
* kill people since humans are the viruses' hosts.

File virus
* have a wide variety of infection techniques and infect a large number of file types.
* infect program files or document files and can be spread any way files are shared.

### agent | virus:

Flu virus
* Many flu viruses exist and are passed from an infected person to the nose or throat of others.
* Some flu viruses are caught from animals.
* are airborne and lodge themselves in nasal passageways.
* can enter the body through the mucous membranes of the eyes, nose, or mouth.
* change all the time
  - every year, so it is advisable to receive a new vaccination each year
* enter the body through the eyes, nose or mouth.
* evolve rapidly.
* have a high mutation rate and evolve much more rapidly than higher plants and animals.
* tend to live longer on surfaces than cold viruses do.
+ Influenza, Changes in the influenza virus: Pulmonology :: Diseases caused by viruses
  * Some flu viruses are caught from animals. These types of flu virus are usually very limited, and while they can make a person very ill, usually other people do not catch the virus from the sick person.

Foamy virus
* appear to occupy a unique niche quite distinct from all other groups of retroviruses.
* bud from both the endoplasmic reticulum membrane and the cell membrane.
* use multiple promoters.

Human virus
* make their way into beach water from a variety of sources.
* mutate and get more deadly.

Icosahedral virus
* are very common plant and animal viruses.
* have cubical symmetry.

Infectious virus
* Some infectious viruses infect tissue.
* can cause severe problems in newborns.
* is difficult to release from scabs except by mechanical grinding.
* much smaller fraction of total viral load.

### agent | virus:

Influenza virus
* Most influenza viruses are transmitted to people.
* Some influenza viruses cause flu
  - seasonal flu
  - have ranges
* affect ferrets.
* are a common cause of respiratory disease in humans around the world
  - almost unique in their ability to spread rapidly around the world
  - classified as type A, B, or C, depending on a nucleocapsid antigen
  - common pathogens
  - notorious for their seasonality
  - species
  - the only members of the orthomyxovirus family
* attach to cells lining the respiratory tract to initiate infection.
* can be quite different from each other
  - mix and match their genes
  - similarly mutate to escape from inhibition by anti-influenza drugs
* cause disease in all age groups
  - important diseases in humans and animals
* causes widespread human disease.
* change constantly
  - continually
  - each year due to genetic mutation
  - often
* disguises itself with a new coat every year.
* infect many parts of the body, including the lungs.
* shedding normally declines rapidly within the first few days of illness.
* undergo two kinds of change
  - types of changes
+ Pathogen: Biology