POX VIRUS
1. Definition of Pox virus.
2. Morphology , pathogenesis and its structure.
3. Mode of transmission of Pox virus.
4. Importance of Pox virus.
Introduction
Pox viruses are largest sized complex
DNA viruses belonging the family pox viridiae, that replicate entirely in the
cytoplasm of vertebrate or invertebrate cells. Clinically important pox viruses
include Variola vaccinia and varicella. Variola is distinguished from
varicella in causing the infection, variolla causes small pox, which is
characterized by the fever develops before the appearance rash while
varicella causing chicken pox developed
with fever and rash simultaneously, vaccine is also called cowpox virus which is closely related to variola,
it cause the mild eruptive disease in cows nevertheless it produces immunity to
the small pox infection when it is transmitted to healthy humans, The word
vaccinia is sometimes used interchangeably with cowpox to refer to the human
from of the disease, sometimes to refer only to the artificially induced human
from of cowpox. Moreover the members of
General characters: Usually
it is a double – stranded DNA orthopox virus. It causes highly contagious
disease called small pox. Approximately more than 500 million people
were killed in the 20th century due to this infection. In United
States, 300 million people were affected. Transmission occurs mainly through
the inhalation of respiratory droplets ( formed by coughing and sneezing )from
infected individuals. Moreover it can be spread through fomites, which are scab
contaminated materials such as bedding and clothing, smallpox only infects
human and cannot survive for more than a few months outside its host under the most
optimal conditions. As it exponentially spreading the disease, it seems to be
an effective bioweapon, it can be stable for hours as an aerosol ( over
24 hours in optimal environmental conditions )and can be produced and stored in
large quantities .The soviet union produced tons of weaponized variola major
per year during cold war, in violation of the 1975 Biological Weapons
Convention.
Morphology : It is an enveloped virus. Inner,
core is present. The core of the virus is dumbbell- shaped; meaning the middle
of the core is narrower than the ends.
The core contains the viral double- stranded DNA and proteins needed to
help uncoat the virus core and replicate the virus. The specific structure of
the smallpox virus will vary based on whether it is inside the cell, outside
the cell, or attached to the cell’s surface.
Virulent Factors: Virulence factors make
an organism dangerous. This organism has two virulence factors namely SPICE
( Smallpox Inhibitor of
Complement Enzymes ), CKBP-II (
secreted chemokine- binding protein, type 2.)
Spice: BIt
enables the virus evade mechanism, it proteins the virus from the attack of
human immune cells. It inactivates machinery of host immune system.
CKBP-II : The
second known virulence factor, CKBP-II ( secreted Chemokine-Binding Protein, type 2),blocks
signals that cell for more immune cells and promote inflammation at the site of
infection.
Pathogenesis :-
Source
·
Patient
·
Nasal secretions
·
Infected droplets, scabs
Symptoms:
Symptoms,
including headache, high fever, malaise and fatigue, begin approximately 12
days after exposure to infection.
Enantham rash : It is an important features of infection that
appears on the infected individual’s mucus membranes (the inside of the mouth,
nose and throat )initially. Later, it
appears all over the body, with higher concentrations of lesions on the face,
arms and legs, this classic pox lesions are firm umbilicated ( indented in the center ),and progress
together through the stage of lesion development ( maculopapular rash , vesicles,
pustules, scabs, scars, ). After 8-9days of the rash, the smallpox pustules
start to develop scab over and fall off. Individuals are less contagious at
this stage nevertheless continue to be contagious until the last scab has
fallen off. Hence permanent scars, blindness, and arthritis can be resulted.
However, the lesions are hemorrhagic, characterized by bleeding sores, or flat,
where the lesions are soft and flat. The mortality rates for these types of
infections are over 95%.
Treatment: Treatment remains
largely experimental. Injection with Vaccinia Immunoglobulin (VIG), antibodies
produced against the vaccinia virus, may help alleviate some symptoms. The
antiviral medication cidofovir may be used in emergency situations, and ST-246,
a new and promising smallpox antiviral , is currently undergoing phase I
clinical trials. In the addition to other supportive care, antibiotics are
given to reduce potential secondary bacterial infections. Vaccination after
exposure to smallpox is protective if given sufficiently early.
Prevention
: In
1796, Edward Jenner developed the first
vaccine against smallpox using material that contained the cowpox virus. The
modern smallpox vaccine contains Vaccinia virus, (unrelated to the cowpox
virus) is administered chickenpox is a highly contagious disease caused by the
varicella-zoster virus (VZV ). It is a DNA virus and is belonging to the family
herpes virus. Primary infections with VZV result in chickenpox. The virus is
believed to have a short survival time in the environment. However chickenpox
can be serious in babies, adults and people with weakened immune system.
Varicella is a relative of the herpes
virus and is present throught the world. Its highly infectious.
Pathogenesis
Mode
of transmission: Touching
the skin of someone with an active rash or Sneezing or coughing touching by
touching the infected person it spreads from one person to another person.
Sneezing
or coughing: While sneezing or coughing the droplet
comes out, that spreads in the air and initiating to develop the infection.
Reinfection: Moreover, this virus
responsible for causing reinfection following the primary infection; it is
occurring in 10-20% of the individuals. In this, virus remains latent in the
cerebral or posterior root ganglia for several decades even after recovery.
Then the virus is reactivated in the ganglion and tracks down the sensory nerve
to the area of the skin innervated by the nerve, producing a varicella from
rash in the distribution of a dermatome. The failure of the host defense
mechanisms to contain the virus in the ganglia after such prolonged periods of
times is not understood however, in immune competent individuals, it is
probably due to the decline effectiveness of previously acquired immunity with
advancing age. Herpes zoster also appears in increasing frequency in
immunocompromised individuals such as those with Hodgkin’s disease and AIDS,
who have effective CMI. Also disseminated herpes zoster is more likely to occur
in such people.
Chickenpox is a highly contagious infection
characterized by an itchy rash made up of red, fluid-filled blisters (pox) and
flu like symptoms. Both the rash and the other symptoms usually can be
effectively treated with over- the counter medication and home remedies,
through an antiviral drug may be prescribed.
Once regarded as an inevitable disease of childhood, chickenpox has
become less common since the advent of the chickenpox vaccine. Through an
initial bout of chickenpox usually resolves in a few days or weeks, the virus
that causes chickenpox never leaves the body and can re-emerge after decades to
trigger a painful illness that are
called shingles in order adults.
Symptoms:
The
most distinctive is the telltale rash, which is occurs about 14days from
exposure. Made up hundreds of red, fluid-filled blisters, the chickenpox rash
first shows up the face, scalp, and torso, and then spreads to the arms and
legs. Because chickenpox is a viral infection, it also causes a cluster of
symptoms similar to the flu, including mild fever, headache, abdominal pain,
fatigue, swollen glands, and overall malaise. Adults who come down with
chickenpox tend to experience these symptoms first and then rash would develop.
Children often get the spots first. “Breakthrough cases,” those that occur
despite vaccination against chickenpox, are usually milder and, in particular,
have fewer rashes.
Complications from the chickenpox infections aren’t
common, and are more likely to occur in adults than children, but they can be
serious. Some possible secondary problems caused by chickenpox include skin infection,
and Reye’s syndrome (related to aspirin use in children).
Lab diagnosis: It can be diagnosed based on the history
of viral symptoms and the characteristic appearance of the rash, because,
sometimes the chickenpox rash can be confused with herpes simples, impetigo,
insect bites or scabies. If there’s any question that rash is the result of
chickenpox, a viral culture can be taken. However, it can take longer to get
the results than for the illness to resolve.
Treatment: A non-steroidal
anti-inflammatory drug (NSAID) such as ibuprofen or acetaminophen can help
bring down a fever and ease headaches and general discomfort.
Dealing with the rash
can be more challenging, especially when it comes to a small child who has a
hard time not scratching their skin. Fortunately, there are lots of options,
including: Soaking in a tube of warm water mixed with colloidal.
Applying calamine
lotion directly to bother-some blisters.
Oral antihistamines
such as Benadry1 (diphenhydramine).
It’s also vital to keep
kids’ fingernails short and very clean.
Sometimes it’s
necessary to treat people who are at risk of becoming seriously ill from
chickenpox, such as those with compromised immune systems. For example, an
antiviral medication called VariZIG (
varicella zoster immune globulin ) may be used.
Prevention: Stay away and keep the
children away from anyone who has chickenpox. Varicella vaccine can be given
with the exception of certain individuals such as pregnant women, however kids
also usually advised to get the varicella vaccine.
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