Essay 41
Poxviridae – the causative agent of smallpox. Adenoviridae. Rhabdoviridae – the
causative agent of rabies. Rotaviridae.
Poxviridae – the causative agent of smallpox
 Poxviridae is a family of viruses. Human serve as natural hosts. There are currently 69
species in this family, divided among 28 genera, which are divided into two subfamilies.
Diseases associated with this family include smallpox.
 Smallpox was an infectious disease caused by either of two virus variants
o Variola major
o Variola mino
 Infection with smallpox is focused in small blood vessels of the skin and in the mouth and
throat before disseminating.
 In the skin it results in a characteristic maculopapular rash and, later, raised fluid-filled
blisters.
 V. major produced a more serious disease and had an overall mortality rate of 15-40%.
V. minor caused a milder form of disease which killed about 1%of its victims.
 The smallpox virus is transmitted mainly through the airborne route and adheres via
droplet spread of viral particles onto the mucosal surfaces of the oropharyngeal and
respiratory tract.
Adenoviridae
 Adenoviruses (members of the family Adenoviridae) are medium-sized (90–100 nm),
nonenveloped (without an outer lipid bilayer) viruses containing a double stranded DNA
genome.
 Their name derives from their initial isolation from human adenoids in 1953
 They have a broad range of vertebrate hosts; in humans, more than 50 distinct
adenoviral serotypes have been found to cause a wide range of illnesses, from mild
respiratory infections in young children (known as the common cold) to life-threatening
multi-organ disease in people with a weakened immune system.
 There are no antiviral drugs to treat adenoviral infections, so treatment is largely directed
at the symptoms (such as acetaminophen for fever)
Rhabdoviridae – the causative agent of rabies. Rotaviridae.
 The name comes from the Greek word Rhabdos meaning “rod”.
 The Rhabdoviridae family include more than 200 pathogens for a variety of mammals. 6
genera with the most significant pathogen being in Genus Lyssavirus causing rabies
and rabies-like viruses.
 They are bullet shaped with a diameter of 70nm, enveloped, negative single stranded
RNA viruses that encode 5 proteins and replicate in cytoplasm.
 Rabies is a viral disease that causes acute inflammation of the brain in humans and
other warm-blooded animals. Early symptoms can include fever and tingling at the site of
exposure.
 These symptoms are followed by one or more of the following symptoms: violent
movements, uncontrolled excitement, fear of water, an inability to move parts of the
body, confusion, and loss of consciousness. Once symptoms appear, death nearly
always results.
 Rabies is spread when an infected animal scratches or bites another animal or human.
Saliva from an infected animal can also transmit rabies if the saliva comes into contact
with the eyes, mouth, or nose. Globally, dogs are the most common animal involved.
 Rotavirus is the most common cause of severe vomiting and diarrhoea among infants
and young children. It is a genus of double-stranded RNA virus in the family Reoviridae.
 There are eight species of this virus, referred to as A, B, C, D, E, F, G and H. Rotavirus
A, the most common species, causes more than 90% of rotavirus infections in humans.
 The virus is transmitted by the fæcal-oral route. It infects and damages the cells that line
the small intestine and causes gastroenteritis
 Rotavirus is usually an easily managed disease of childhood. Nearly every child in the
world has been infected with rotavirus at least once by the age of five.
 Treatment of acute rotavirus infection is nonspecific and involves management of
symptoms and, most importantly, maintenance of hydration.
 Depending on the severity of diarrhoea, treatment consists of oral rehydration, during
which the child is given extra water to drink that contains small amounts of salt and sugar