L3: RNA VIRUS 2 (PT1)

paramyxoviridae

• pleomorphic

• envelope is fragile thus labile to storage conditions

• genome is not segmented thus no frequent gene reassortment (no antigenic shift)

• follows the rule of six

nucleocapsid

• n, contains the genomic rna

phosphoprotein

• p, binds to the n and l proteins and forms part of the rna polymerase complex

matrix

• m, organizes and maintains virion structure

fusion

• f, mediated cell entry

hemagglutinin

• h, possessed by morbilivirus, for hemaggkutination

hemagglutination-neuraminidase

• hn, respiroviruses, rubulaviruses, and avulavirus

glycochon

• g, neither h nor n; assign with henipavirus, pneumovirus

large polymerase

• l, catalytic subunit for rna-dependent rna polymerase

parainfluenza virus

• causes mild or severe upper and lower respiratory tract infections, particularly in children

• transmission is by droplets or direct contact, the virus disseminates locally in the ciliated epithelial cells of the respiratory mucosa

• common colds, bronchitis, bronchiolitis, croup

mumps virus

• rubularvirus

• viral parotitis, swelling of the salivary glands, especially the parotid glands

• the single serotype of mumps virus antigens with parainfluenza viruses, particularly type 1

• spread in droplet, primary infection consists of viremia and involvement of glandular and nervous tissue, resulting in inflammation and cell death

• involves cellular and humoral immune responses, which confer lifelong immunity

• endemic in late winter and early spring

mumps orchitis

• pain and swelling of the testicles which normally begins 4-8 days after swelling of the parotid

• most common complication of mumps in post pubertal men, affecting about 20-30% of cases

• rarely leads to sterility but it may contribute to subfertility

measles virus

• morbilli virus/rubeola virus

• possess 1 antigenic type

• causes viremia with wide dissemination and multiplies in cells of the lymphatic, respiratory, intestinal and urinary system, the skin, and sometimes the brain

• cell mediated immunity is essential to control of infection, antibody is not sufficient due to measles ability to spread cell to cell

• ip: 8-12 days

koplik spots

• grayish white dots with red border, opposite the lower molars

respiratory syncitial virus

• common cause of upper and lower respiratory tract disease in young children, divided into types a and b

• transmission is by droplets or direct contact

• infects the ciliated epithelial cells of the respiratory mucosa and disseminates locally

• is caused partly by immunopathologic antibody-dependent cellular cytotoxicity

picornaviridae

• compromises five genera

• do not have a common group-specific antigen; have many serotypes

• capsid contains of 60 copies of ech viral chons (vp 1-4)

poliovirus

• belongs to the enterovirus c species

• has served as a model picornavirus in many laboratory studies of the molecular biology of picornavirus replication

• inactivated when heated at 55 deg celsius for 30 minutes

poliomyelitis

• infectious disease transmitted by fecal oral contamination with lymphatic replication

• mainly affects children under 5 years of age

• one in 200 infections leads to irreversible paralysis

• among those paralyzed, 5-10% die when their breathing muscles become immobilized

• primarily impacts developing countries with poor sanitation

mild disease

• most common form of disease

• has only a minor illness, characterized by fever, malaise, drowsiness, headache, nausea, vomiting, constipation, and sore throat in various combinations

nonparalytic poliomyelitis

• has stiffness and pain in the back and neck

• lasts 2-10 days, and recovery is rapid and complete

• associated with aseptic meningitis

paralytic poliomyelitis

• flaccid paralysis

• maximal recovery usually occurs within 6 months, with residual paralysis lasting much longer

immunity

• is permanent to the virus type causing the infection and is predominantly antibody mediated

• (passive) transferred from mother to offspring

coxsackie virus

• differentiated from other groups of picornaviruses by their pathogenicity for mice and by classification of their antigenicity

• the incubation period of coxsackievirus infections ranges from 2-9 days

• ranges from mild febrile illness to central nervous system, skin, cardiac, and respiratory diseases

coxsackie a

• aseptic meningitis

• respiratory and undifferentiated febrile illness

• herpangina (vesicular pharyngitis)

• hand and foot and mouth disease

• acute hemorrhagic conjunctivitis

coxsackie b

• pleurodynia

• myocarditis

• pericarditis

aseptic meningitis

• group a coxsackieviruses, most commonly a7 and a9

• fever, malaise, headache, nausea, and abdominal pain are common early symptoms

• the disease sometimes progresses to mild muscle weakness suggestive of paralytic poliomyelitis

• patients almost always recover completely from nonpoliovirus peresis

herpangina

• acute febrile illness with small ulcerative or vesicular lesions in the posterior oropharynx

• the illness is self-limited and most frequent in small children

• the disease is highly contagious, and most cases are reported in the summer months

hfmd

• characterized by oral and pharyngeal ulcerations and a vesicular rash of the palms and soles that may spread to the arms and legs

• vesicles heal without crusting, which clinically differentiates them from the vesicles of herpesviruses and poxviruses

• may be recovered not only from the stool and pharyngeal secretions but also from vesicular fluid

• not to be confused with foot and mouth disease of cattle, caused by an unrelated picornavirus that does not infect humans

pleurodynia

• fever and stabbing cheat pain are usually abrupt in onset but are sometimes preceded by malaise, headache, and anorexia

• the chest pain may last from 2 days to 2 week s

• abdominal pain occurs in approximately half of cases, and in children this may be the chief complaints

• the illness is self limited and recovery is complete, though relapses are common

echovirus

• enteric, cytophatic, human, and orphan viruses which produces cytopathogenic effects in cell cultures they infect the human enteric tract

• can be recovered from humans only by inoculation of certain tissue cultures

• identified by neutralization tests as serotypes

• aseptic meningitis, encephalitis, febrile illnesses with or without rash, common colds, and ocular disease are among the diseases

rhinovirus

• common colds virus

• natural hosts of rhinoviruses are humans and chimpanzees

• present in the nose and pharynx

• they are inactivated at ph 3.0 and have an optimum growth temperature of 33 deg celsius

• at least 115 serotypes are known

• more than 90 percent of susceptible individuals infected with rhinoviruses succumb to the infection

• secondary bacterial infections with strep and haemophilus may result in sinusitis and otitis media

reoviridae

• respiratory and enteric orphan virus

• they are currently 97 species in this family, divided among 15 genera in two subfamilies

• infections occur often in humans, but most cases are mild

• transmission under natural circumstances involved respiratory aerosols and secretions and fecal oral transmission

• have a unique structure which contains a glycosylated spike protein on the surface

• are also generally stable at temperatures below room temperatures in aerosols, especially in the presence of high relative humidity

• capable of spreading in the host by means of the lymphatic system, through the bloodstream or via axoplasmic transport within neurons

rotavirus

• wheel appearance

• most common cause of diarrheal disease among infants and young children (6 months-2 years old)

• nearly every child in the world is infected with a rotavirus at least once by the age of five

• transmitted by the fecal oral route, contact with contaminated hands, surfaces and objects and possibly by the respiratory route

• infects and damages the cells that line the small intestine and causes gastrienteritis

• survive between 9-19 days

rotavirus gastroenteritis

• mild to severe disease characterized by nausea, vomiting, watery diarrhea, and low grade fever

• ip: two days before symptoms apprear

• symptoms often start with vomiting followed by four to eight days of profuse diarrhea

rhabdoviridae

• are uniquely bullet-shaped

• very stable to drying

• do not have hemagglutinating and neuraminidase activities

• carry genes for five proteins: large proteins, glycoprotein, nucleoprotein, phosphoprotein, and matrix protein

• generally introduced through a bite wound

rabies (lyssavirus)

• zoonotic acute infections causing cns infection to humans and wild animals

• was historically referred to as hydrophobia due to the symptoms of panic when presented with liquid to drink

• ip: 1-3 months (7 days to more than a year)

• present on all continents except antartica, with over 95% of human deaths occurring in asia and africa

• can survive on inanimate objects for as long as it takes the saliva to completely dry

furious rabies

• characterized by hyperactivity and hallucinations

paralytic rabies

• characterized by paralysis and coma

prodormal

• flu-like illness headache, paresthesia

encephalitic

• excessive motor activity, hypersensitivity to bright light, loud noise, hyper-salivation, dilated pupils

brainstem dysfunction/paralytic

• dysphagia, hydrophobia, apnea