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What are herpesviruses?
are enveloped DNA viruses
over 100 members in this group
many causes illness in humans
common illnesses caused by herpesviruses are:
herpes simplex 1
herpes simplex 2
varicella zoster
Epstein Barr
human cytomegalovirus infection
What is Herpes simplex 1 and 2?
generally referred to as herpes
HS1 causes oral herpes
HS2 causes genital herpes
tend to cause latent infections
after the initial infection, they stay dormant in neurons until some environmental factor causes their reactivation
resulting in the host experiencing another outbreak of symptoms
What is varicella zoster?
is responsible for both chickenpox (varicella) and shingles (herpes zoster)
bc of variations, chicken pox and shingles are becoming increasingly rare
prior to vaccines, the course of disease was:
initial infection occurred sometime in childhood
followed by an uncomfortable, mid/moderate illness that lasts 1 to 2 weeks
once the initial illness is resolved, the virus stays dormant for years/decades
once a person reaches their 50s or 60s, the virus is often reactivated and causes a second course of infection called shingles
What is Epstein Barr virus?
is very common
most adults show evidence of having been infected atleast once, even unknowingly
in some people, the virus causes a mild illness that doesn’t require any medical intervention
in others it leads to a case of mononucleosis that warrants treatment
most fully recover from the associated illness but have lingering effects
some may even develop cancer as a result of persistent or repeated infection
What is human cytomegalovirus?
another common virus
generally doesn’t cause serious problems for people
however, those who are immunocompromised or pregnant can experience more serious consequences from infection
people w/ weakened immune systems may experience problems with vision, digestion, pneumonia, or encephalitis bc of the virus
infants that become infected before birth may experience liver problems, microencephaly, jaundice, seizures and a variety of other health issues
What is the papilloma virus?
are a very large group of non-enveloped DNA viruses
more than 100 species and capable of infecting animals
most are relatively harmless
cause different types of warts
they can be uncomfortable sometimes, but generally do not cause serious health effects
some strains of papilloma can lead to cancer
particular strains are associated with cancers of the cervix, oral cavity, and genital regions
a vaccine has been developed that helps prevent some of these infections
has led to a lowered incidence of these types of cancers
What are influenza viruses?
enveloped RNA viruses
can infect a variety of species
prone to a relatively high rate of mutation
divided into 4 main categories, A-D
types A and B are most likely to cause widespread human infections
type A leads to pandemics because it can spread human to animals as well as human to human
type B can also cause serious infections but can only spread from human to human and hasn’t been associated with any pandemics
type C can infect humans and causes mild illness
type D doesn’t infect humans
has 2 surface antigens :hemagglutinin (H) and neuraminidase (N)
are important virulence factors
play a role in entry and exit of the target, causes red blood cells to clump together
have several varieties and the combinations are always changing
meaning the antibodies from a previous infection might not be protective for a new infection
What is Human Immunodeficiency Virus (HIV)?
found on every continent except antarctica
killed atleast 32.7 mil people
no cure and no vaccine for this viral infection
the only medications can only keep viral levels in the body low but not eliminate them
belongs to retroviruses group
enveloped RNA viruses that synthesize DNA from RNA once they enter a host cell
is then “pasted” into a host cell chromosome (the viral DNA becomes part of the host DNA, and when the host DNA is copied, it passes on the viral DNA too
is one of the reasons HIV cannot yet be eliminated from the body
basically this virus becomes part of the person it has infected
the main cells that become infected are: T-helper cells (CD4 cells)
normally assist in immune activities (activating B cells, that create antibodies and create long-term immunologic memory)
once these cells are infected, the body’s immune system weakens over time
if HIV isn’t treated with anti-retrovirals, the person’s immune system will soon not even be able to fight off mild infections
in which case their condition turns into AIDS (acquired immunodeficiency syndrome)
while HIV can be treated, AIDS cannot and that person will die
What is polio?
causing disease since Egyptian times
was common and widely spread due to industrialization
is transmitted through the fecal-oral route, even indirectly like food or water
when the virus is excreted from the body of one person and ingested by another
the virus multiplies mainly in the intestines of the recipient
then travels through the blood to the central nervous system
once it reaches the CNS, it starts to destroy motor neurons, especially those responsible
for the extremities and breathing
some people may be asymptomatic while they’re infected, others may develop a mild flu-like illness, and others may die
is no longer common in the US and other developed regions
however, Africa, India, and the Middle East where the disease breaks out periodically
despite word-wide eradication efforts via vaccines
What is Rotaviruses?
non-enveloped RNA viruses
cause 200,000 deaths (almost all children) every year
several subtypes:
type A: causes most of the diseases in humans
when someone’s infected, typical symptoms include:
large amounts of watery diarrhea
leading to dehydration and death
for children who survive this illness but become chronically infected, permanent damage to the intestinal lining may happen and lead to malnutrition
most kids recover from rotavirus infections realtively quickly and easily (in US/developed countires)
cases may become fatal (in undeveloped countries)
there is a vaccine that prevents most serious cases of disease in children who receive it
features ALL rotaviruses have:
a double capsid (extra difficult to destroy w/ standard disinfection
What are measles, mumps, and rubella?
these viruses are not closely related, but they are prevented by a combined vaccine (MMR)
Measles
one of the most contagious diseases
spread via respiratory droplets
after an incubation period of 1-2wks, people usually develop a characteristic rash and symptoms of respiratory illness
includes cough, runny nose, and watery eyes, high fever as well
most people recover and maintain life-long immunity
some people may be left with permanent disability or die
Mumps
characterized by swelling of the salivary glands near cheek and jawline
someone may experience swelling on 1 or both sides of their face
usually goes away w/in 2 wks and person makes a full recovery during that time period
some people may also experience a fever, a headache, muscle soreness, and other general symptoms of tiredness and body aches
this infection may also possibly cause inflammation of the testicles, ovaries, pancreas, or even brain all have long-lasting consequences
Rubella
German measles
another generally mild illness
can cause serious complications for developing fetuses
if a pregnant woman is exposed to and infected with this virus, once born the baby may experience problems like:
heart defects
hearing difficulties
eye problems
cognitive difficulties
growth problems
although immunization prevents most cases of congenital rubella symptoms
with declining rate of vaccination, its possible we’ll see more cases in the next few decades
What is Hepatitis? What types are there?
an inflammation of the liver
caused by a variety of factors, including viral infections
3 main viruses that cause viral hepatitis
though they aren’t closely related from a genetic perspective
the ALL infect the liver and cause inflammation
Hepatitis A
Hepatitis B
Hepatitis C
What is Hepatitis A?
a Picornavirus transmitted through the fecal-oral route, typically via food and water
once entering the GI tract, the virus moves into the blood stream and enters the liver
then it multiplies and causes an inflammatory response
typical signs and symptoms:
nausea, vomiting, diarrhea, abdominal pain, general fatigue, and fever
many people have no symptoms, those that do generally recover on their own quickly
its uncommon but IS possible for this virus to cause severe damage to the liver and/or induce liver failure
there is a vaccine for this type of hepatitis
in unvaccinated communities, this disease can be prevented via handwashing and other sanitation techniques
What is Hepatitis B?
an enveloped DNA virus
spread via body fluids
blood, semen, and vaginal secretions can all spread the virus
the illness is mild and self-limiting
may experience abdominal pain, nausea, fatigue, and jaundice that eventually goes away as the body fights the infection
these people are usually treated with supportive care that helps ease symptoms and makes their pain level decrease
for some people, this infection can become chronic and lead to liver cirrhosis/liver cancer
they are treated with antiviral medications and monitored for indications of cirrhosis and cancer
there is a vaccine that can prevent infection
standard precautions preventing/limiting the exchange of bodily fluids help decrease transmission too
What is Hepatitis C?
an enveloped RNA virus that causes typically the most serious form of viral hepatitis
this virus is passed from person to person via blood
most cases of transmission happen via equipment used to inject drugs (needles are common, straws too)
for years, hepatitis C wasn’t able to be cured and the infection often lead to cirrhosis and liver cancer
people w/ this virus could manage symptoms w/ various medications, but nor cure and was fatal often
recent developments in pharmacology have led to the development of a medication that can cure the disease in most people
however still no vaccine
however the new medication have a chance at clearing the virus from their body and not suffering permanent damage to their livers
What are prions?
infectious pieces of proteins
unique among microbes because:
they have no lipids, carbs, nucleic acids
they’re very similar in structure to proteins found w/in the membranes of cells in the CNS
is similar enough that the immune system does not appear to recognize them as foreign invaders
different enough that when the prions insert themselves into the cell membrane, it causes them to lose their shape and fall apart
this is when the immune system tries to clear the damaged cells
resulting in holes, which get larger as the disease progresses
general symptoms of prion infections include:
confusion, fatigue, difficulty with coordination (walking/talking), hallucinations, and others depending on the prion
as of right now, prion diseases are always fatal
we don’t always know how prion infections are transmitted
sometimes from contaminated food products, genetic component, some may be transmitted during organ/tissue transplants, other times it’s a mystery
What are different prion infections?
Creutzfeldt–Jakob Disease
15% of cases are hereditary in nature
other people, those who have undergone medical procedures and received certain tissue types (nervous tissue)
other people acquire this via unknown reasons
symptoms include:
depression, agitation, difficulty walking, and disorientation
Kuru
the prion that causes this disease was the first prion discovered
remains one of the most sensational infectious agents
in some cultures, it was common to consume certain body parts, especially the brain of deceased relatives
has a long incubation period, once it manifests, the person usually starts to have trouble walking/standing, coord. problems, headaches, tremors, and may sometimes have incontrollable fits of laughter
Fatal familial insomnia
cases always seem to be hereditary
the gene that causes it is found in ~40 families worldwide
this specific prion damages the thalamus, partly responsible for sleep
once this disease starts, ~40yrs, there is a progressive loss in the ability to sleep
though insomnia is often the most noticeable symptom at first
symptoms can also include conditions like difficult walking and thinking clearly
eventually, the brain damage this prion causes becomes so complete and the lack of sleep so pervasive, the person dies
bovine spongiform encephalopathy
aka mad cow disease
the source of this prion is infected beef
if a person consumed infected beef w/ this prion, they will develop BSE
this prion has an incubation period of ~12yrs (can be more/less)
once symptoms start, the progression is usually quick and people often experience difficulty with:
vision, abnormal muscle movements, problems with balance and coord., and personality changes