Download RNA Viruses

Viruses
Hepatitis
All different viruses—commonality is that they cause inflammation of the liver
Hepatitis A
 The hepatitis A virus is a picornavirus; it is non-enveloped and contains ssRNA
 Transmission is eating or drinking food or water contaminated with infected
feces. Shellfish which have not been sufficiently cooked is a relatively common
source.
Hepatitis B
 A member of the hepadnavirus family.[ The virion consists of an outer lipid
envelope and an icosahedral nucleocapsid core.
 made of circular DNA, but it is unusual because the DNA is not fully doublestranded.
 transmitted by exposure to infectious blood or body fluids
Hepatitis C
 Small, enveloped, single-stranded, positive-sense RNA virus member of the
Hepacivirus genus in the family Flaviviridae.[
 About 80% of those exposed to the virus develop a chronic infection
 transmitted by exposure to infectious blood or body fluids
Hepatitis D
 The HDV is a small, spherical virus with a 36 nm diameter of the genus
Deltavirus. It has an outer coat containing three HBV envelope proteins (called
large, medium, and small hepatitis B surface antigens), and host lipids
surrounding an inner nucleocapsid. The nucleocapsid contains single-stranded,
circular RNA
 The vaccine for hepatitis B protects against hepatitis D virus because of the
latter's dependence on the presence of hepatitis B virus for it to replicate
Hepatitis E
 HEV is a positive-sense single-stranded RNA icosahedral virus
 transmitted mainly through contaminated drinking water
 the first vaccine to prevent hepatitis E infection was registered in China (not
approved in US))
Virus Tissue Tropism
• Targeting of the virus to specific tissue and cell types
• Receptor Recognition
 CD4+ cells infected by HIV
 CD155 acts as the receptor for poliovirus
DNA Viruses
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Herpesviridae
Poxviridae
Herpesviridae
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Causes diseases in animals
The family name is derived from the Greek word herpein ("to creep"), referring
to the latent, recurring infections typical of this group of viruses. (Can cause lytic
or latent infections)
Causes diseases in animals
The family name is derived from the Greek word herpein ("to creep"), referring
to the latent, recurring infections typical of this group of viruses. (Can cause lytic
or latent infections)
More than 90% of adults have been infected with at least one of these, and a
latent form of the virus remains in most people.
All herpesviruses are enveloped viruses composed of relatively large doublestranded, linear DNA encoding 100-200 genes encased within an icosahedral
capsid.
Causes diseases in vertebrates and invertebrates
Five species of Herpesviridae –
• HSV-1 and HSV-2 (both of which can cause orolabial herpes and genital
herpes),
• Varicella zoster virus (which causes chicken-pox and shingles),
• Epstein-Barr virus (which causes mononucleosis)
• Cytomegalovirus
Poxviridae
Smallpox
• Variola is a large brick-shaped virus measuring approximately 302 to 350 nm by
244 to 270 nm, with a single linear ds DNA of 186 (kbp) in size.
• The life cycle of poxviruses is complicated by having multiple infectious forms,
with differing mechanisms of cell entry.
• Poxviruses are unique among DNA viruses in that they replicate in the cytoplasm
of the cell rather than in the nucleus.
• In order to replicate, poxviruses produce a variety of specialized proteins not
produced by other DNA viruses, the most important of which is a viral-associated
DNA-dependent RNA polymerase.
• Smallpox in the New World
• In the early 16th century smallpox began to imported into the western
hemisphere.
• The Spanish inadvertently owe success in conquering the Aztec and Incas
in Mexico to smallpox.
• Smallpox arrived in North America via Canada, and Mexico.
• The disease killed an estimated 400,000 Europeans annually during the
closing years of the 18th century (including five reigning monarchs), and
was responsible for a third of all blindness.
Of all those infected, 20–60%—and over 80% of infected children—died
from the disease. Smallpox was responsible for an estimated 300–500
million deaths during the 20th century.
• As recently as 1967, the WHO estimated that 15 million people contracted
the disease and that two million died in that year.
Smallpox as Biological Warfare
• Lord Jeffrey Amherst, Commanding General of British Forces in North
America during the French and Indian War. (1754-1763)
• Used blankets (smallpox blankets) coated with smallpox dust as germ
warfare to wipe out the Native American population.
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RNA Viruses
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RNA viruses can be further classified according to the sense or polarity of their
RNA into negative-sense and positive-sense, or ambisense RNA viruses.
Positive-sense viral RNA is similar to mRNA and thus can be immediately
translated by the host cell
Negative-sense viral RNA is complementary to mRNA and thus must be
converted to positive-sense RNA by an RNA polymerase before translation.
Purified RNA of a positive-sense virus can directly cause infection though it may
be less infectious than the whole virus particle
Purified RNA of a negative-sense virus is not infectious by itself as it needs to be
transcribed into positive-sense RNA; each virion can be transcribed to several
positive-sense RNAs.
Ambisense RNA viruses resemble negative-sense RNA viruses, except they also
translate genes from the positive strand.
Poliovirus
• Enterovirus.
• + stranded RNA virus
• Transmitted by the faecal oral route.
• Cause of gastrointestinal illness and poliomyelitis.
Influenza A virus
• Myxovirus
• Enveloped RNA virus
• Infects a wide range of animals other than humans
• Undergoes extensive antigenic variation
• Major cause of respiratory infections
Norovirus
• Genus of genetically diverse ssRNA, non-enveloped viruses in the Caliciviridae
family
• The known viruses in the genus are all considered to be the variant strains of a
single species called Norwalk virus.
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The viruses are transmitted by fecally contaminated food or water, by person-toperson contact, and via aerosolization of the virus and contamination of surfaces.
Noroviruses are the most common cause of viral gastroenteritis in humans, and
affect people of all ages.
Rotovirus
• Genus of dsRNA virus in the family Reoviridae.
• 11 unique double helix molecules of RNA which are 18,555 nucleotides in total.
Each helix codes for a protein.
• The RNA is surrounded by a three-layered icosahedral protein capsid. Viral
particles are up to 76.5 nm in diameter and are not enveloped.
• Nearly every child in the world has been infected with rotavirus at least once by
the age of five.
• There are five species of this virus, referred to as A, B, C, D, and E. Rotavirus A,
the most common species, causes more than 90% of rotavirus infections in
humans.
• Transmitted by the fecal-oral route. It infects and damages the cells that line the
small intestine and causes gastroenteritis.
HIV
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HIV is a member of the genus Lentivirus part of the family Retroviridae.
ss positive-sense, enveloped virus
HIV is different in structure from other retroviruses. It is roughly spherical[ with a
diameter of about 120 nm, around 60 times smaller than a RBC yet large for a
virus.
Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, preejaculate, or breast milk.
Within these bodily fluids, HIV is present as both free virus particles and virus
within infected immune cells.
HIV infects vital cells in the human immune system such as helper T cells
(specifically CD4+ T cells), macrophages, and dendritic cells.
Ebola
• Ebolavirions are filamentous particles of ssRNA that may appear in the shape of
a shepherd's crook or in the shape of a "U" or a "6", and they may be coiled,
toroid, or branched.
• The current outbreak in west Africa, (first cases notified in March 2014), is the
largest and most complex Ebola outbreak since the Ebola virus was first
discovered in 1976. There have been more cases and deaths in this outbreak
than all others combined.
• As of Oct 8, 2014:
• Total Cases: 8400
• Laboratory-Confirmed Cases: 4656
• Total Deaths: 4033
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Cells lining the inside of blood vessels (endothelial cells), macrophages,
monocytes and liver cells are the main targets of infection.
After infection, a secreted glycoprotein, known as small soluble glycoprotein
(sGP) or as the Ebola virus glycoprotein (GP), is synthesized
Human-to-human transmission occurs only via direct contact with blood or body
fluid from an infected person (including embalming of an infected dead body), or
by contact with objects contaminated by the virus, particularly needles and
syringes.
Other body fluids that may transmit ebolaviruses include saliva, mucus, vomit,
feces, sweat, tears, breast milk, urine, and semen.
Entry points include the nose, mouth, eyes, or open wounds, cuts and abrasions
Humans are not infectious until they develop symptoms.
Symptoms usually begin suddenly with an influenza-like stage characterized by
fatigue, fever, headaches, and pain in the joints, muscles, and abdomen.
Vomiting, diarrhea, and loss of appetite are also common.
Less common symptoms include sore throat, chest pain, hiccups, shortness of
breath, and trouble swallowing.
The average time between contracting the infection and the start of symptoms
(incubation period) is 8 to 10 days, but it can vary between 2 and 21 days
In the bleeding phase, which typically begins five to seven days after first
symptoms,internal and subcutaneous bleeding may present itself in the form of
reddened eyes and bloody vomit and/or stools.
People remain infectious as long as their blood and body fluids, including semen
and breast milk, contain the virus. Men who have recovered from the disease can
still transmit the virus through their semen for up to 7 weeks after recovery from
illness
The disease is only spread by direct contact with the secretions from someone
who is showing signs of infection
A person's ability to spread the disease is often limited as the individual is often
too sick to travel during the infectious stages of the disease.
As transmission via air is generally ruled out, the possibility of transmission
between non-seat-mate airline passengers is generally ruled out, unless the
patient is symptomatic with sweating, vomitus, etc.
What about pets?
• In the 2001-2002 outbreak in Gabon, scientists found signs of the virus in
25% of the dogs living near the outbreak. The animals were not
symptomatic, nor did they die during the time the scientists were studying
them.
• So..the animals came in contact with Ebola virus and their immune
systems responded.
• Whether or not dogs shed Ebola once their immune systems encounter it
remains to be seen.
• Scientists are studying the pets of the infected humans currently.
• Cats have not found to contract virus.
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At this time, there have been no reports of dogs or cats becoming sick
with Ebola or of being able to spread Ebola to people or other animals.
Even in areas in Africa where Ebola is present, there have been no reports
of dogs and cats becoming sick with Ebola.
did hospital workers contract virus?
There are only 5 hospitals that really are equipped to handle Ebola
patients. The Dallas hospital is not one of them.
Decontamination procedures and the “buddy-system” were not used...