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Better than WebMD submitted 2010.07.11 10:47 AM by Stixs viewed 1838 times


Let's talk about medically relevant viruses.

Yes, I'm serious.

...Hey, don't walk away!...I'll put an interesting picture in if you at least pretend to be interested! Ok? Ok...


So, what are viruses? They're not bacteria, they're not fungi, they're not parasites (worms). Are they living?

No.

Viruses are non-living particles.

What does it mean to be living? You can replicate on your own, via sexual or asexual means, and you supply your own energy in some way (or at least provide the given cellular machinery to steal it from something else). Viruses do neither.

So what is a virus, then...

A virus is a small section of genetic material, often DNA or RNA (the difference between the two is irrelevant for a pH post, but I'd be happy to describe it if you want...), surrounded by a protein coat called a Capsid. There are many viruses that are also surrounded by a membrane that they steal from the host cell (the cell they infect) as they exit it/kill it. This membrane is called an envelope. They also often have several enzymes necessary to hijack host cells and use them for evil...

So this genetic material does not actually allow the virus to do anything other than produce whatever enzymes are necessary for it to survive in a host cell, and later replicate. For example, HIV has three genes: Gag, for its membrane glycoproteins (what it uses to attach to cells); Pol, for its enzyme that allows its genetic material to be used; and Env, for its membranous envelope. Not so scary now, is it?

Anyhow, I'm explaining all of this so that you guys understand what I get into later. There's no quiz, so don't worry about the details.

I mentioned that viruses have some way to attach to cells. This is key to a virus's functionality, because otherwise, they would continue to exist out in the environment. In fact, in a virus's life-cycle, this is the first, and most important step, followed by entering the cell, taking it over, reproducing, and then exploding the cell as 100s and 100s of replicated viral progeny exit at once.

So all of this is fine and dandy, but who cares about nitty gritty?!

Let's get to actual examples, after this short bathroom break

INTERMISSION

Everyone good?

Alright. I'm going to divide this based on basic classification, like DNA or RNA and Enveloped or non-enveloped (does it have a membrane or not)

There aren't that many that are medically relevant, so don't worry...and I figure that this is a nice way for you to get some idea of what you're infected with if you start to freak out about weird symptoms

Let's start!

RNA Non-Enveloped Viruses
- Picornovirus - the smallest set of viruses, and most often cause systemic infections.
There are several subspecies here:
-- Rhinovirus - Common cold. There are 1000s of these, which is why there is no cure
- -HAV - Hepatitis A virus. Causes Hepatitis A, which is usually self-limiting. Spread by feces
- -Poliovirus - Smallest of the small. Causes Poliomyelitis (Polio)
- -Coxsackie A Virus - Causes Hand-Foot-Mouth disease and Herpangina
- -Coxsackie B Virus - Spread through feces. Causes myocarditis, pericarditis and aseptic meningitis (heart and brain disorders)
- Calciviruses
-- Norwalk virus - Adult gastroenteritis (bowel infection)
-- HEV - Hepatitis E virus. Also spread through feces
- Reovirus - These viruses have an interesting shape, but that's about it
--Rotavirus - Infant gastroenteritis
--Coltivirus - Colorado Tick Virus, causes Colorado Tick Fever. Don't visit Colorado...

RNA Enveloped Viruses
- Filovirus - Ebola
- Flavivirus - These are all strange Asian Viruses, and Hepatitis C
-- Japanese Encephalitis Virus - Causes Encephalitis. Most common viral cause
-- West Nile Virus - Also causes encephalitis. Transmitted via mosquitoes
-- Yellow Fever Virus - You guessed it...yellow fever
-- HCV - as promised, Hepatitis C
- Rhabdovirus - Rabies!
- Bunyavirus - Hanta!
- Coronavirus - SARS
- Deltavirus - Hepatitis D, which is really a parasite of the Hepatitis B virus, a DNA Hepadnovirus
- Paramyxovirus - Causes Parainfluenza, RSV in infants (respiratory synctitial virus), Measles and Mumps
- Orthomoxyvirus - Influenza. This bad boy is particularly virulent because it has several glycoproteins that give it differing properties (making it very difficult to make a vaccine, which is why there are new ones every year). These GPs, FYI, are called Hemagluttinin and Neuraminidase. They act as signals to our immune system telling it to eat shit and die, which pisses it off.
- Retroviruses - HIV
- Togaviruses - Other than causing equine encephalitis, it is responsible for German Measles (aka Rubella)

DNA Non-Enveloped Viruses
- Parvovirus - causes aseptic anemia in people with sickle cell anemia
- Papovirus - HPV. Cause of warts and cancer.
- Adenovirus - Causes cold, pneumonia, meningitis, pharyngitis and conjunctivitis

DNA Enveloped Viruses
- Hepadnovirus - Hepatitis B. The most dangerous one because of virulence, but HCV is the most common cause of liver transplants...so hope you get HAV if you must get one of them.
- Herpesvirus - Herpes and all of its cousins
--HSV1 - Herpes above the waist
--HSV2 - Herpes below the waist
--HSV3 - VZV, aka Chickenpox; and its adult counterpart, Shingles
--HSV4 - Epstein-Barr Virus - Mononucleosis, Hairy leukoplakia, Burkitt's Lymphoma (unless you're an African child, you won't be affected), and Nasopharyngeal cancer
--HSV5 - Cytomegalovirus - the most common cause of viral mental retardation
--HSV8 - Causes Kaposi's Sarcoma in immunocompromised patients
- Poxvirus - Largest DNA virus. Causes Smallpox. Eradicated :-)


So that was a lot of information. Don't worry about memorizing it.


How can you fight these viruses? Often, once infected, you can't do too much, but you can get vaccinated against many of them

For example, the MMR Vaccine, which uses live viral particles that cannot actually harm you, vaccinates against Measles, Mumps and Rubella. You can also get a live-viral (Salk) or a killed-viral (Sabin) vaccine against polio!

In short, Viruses are scary because they're not actually living, and yet they wreak havoc. Get your kids immunized. They cannot get autism. That study was debunked. Don't be a crazy person.

Picture time!



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