8 Flashcards
how do viruses multiply
synthesis of nucleic acid and protein then used to build virus particle
do viruses have metaboilsm
no they need other cells to grow
4 basic components of viruses
nucleic acid
protein capsule
protect core w/antigen inside
carries genetic code
3 ways viruses can grow
- cell cultures
- embryonic eggs
- living animals
if a viruses is able to grow using one method is it possible to grow them on another?
no
5 steps of replication for viruses
- adsorption- virus adheres to cell wall
- injection- releases viral particle material in cell and looses it’s protein coating (eclipsed)
- synthesis- use of cell to create immature viral components
- maturation- ineffective virus mature in cell using nucleic acids and proteins to build them up
- release- may leave the cell by lysis or budding through cell membrane
what is the golden rule of viruses
they die quickly in clinical media.
must be examined and inoculated quickly.
refrigerate don’t freeze
how do we detect a virus
a. detection of virus itself
b. detection of immune reactions produced by host cells; draw blood for antibodies
ways to use detection of virus in clinical specimen
- E.M electron microscopy (since viruses are invisible to light
- multiplication
- direct detection of virus by clinical specimen immunological methods
detection of virus in clinical specimen (multiplication effects)
cytopathic effect: visual modification of cell
hemagglutination: agglutinate red blood cells
immunofluorescent and other serological method approaches
ways to detect/identify viruses using patient
immunity test- presence or absence of antibodies
diagnostic test- rise of antibody titer
5 respiratory viruses
- influenza
- parainfluenza
- respiratory syncytial
- rhinoviruses
- coronaviruses
- echoviruses, coxsackie virus, herpes virus
what is the difference between influenza A and B
A. cause major epidemics
B. milder disease; occasionally causes epidemics
why is antigenic variability so common in respiratory viruses
nucleic material is made of separate connected fragments that recombinant with other fragments allowing variability of antigen
clinical symptoms of influenza virus. Who is at risk?
acute febrile illness (fever lasting for about 2-7 days)
infants and elderly
how to diagnose influenza
throat washing (nasopharyngeal aspirate)
pairing sera acute and convalescent phase
taken 14-21 days apart, if there is a large rise or fall in Ab production sign of infection
how to prevent influenza
get a vaccine dummy
antiviral drugs available for type A influenza
respiratory illness that affects infants and small children, causes croup (barking cough, high pitch), cause bronchiolitis and bronchopneumonia. No vaccine available
parainfluenza viruse
respiratory illness, affecting children under 2.
symptoms include bronchiolitis and pneumonia; occasionally fatal
is known to cause epidemics
no vaccine
given ribavizine
respiratory syncytial virus
rhinovirus
“common cold”
> 100 serological species
no cross immunity, so infection is common
how to detect a respiratory virus
- fastest approach direct detection using immunofluorescence and inoculation of virus
- clinical specimens in order of usefulness: nasopharyngeal aspirate, throat wash, cotton swab
- difficult to identify after few days
3 public health measure for respiratory illnesses
- identify antigenic makeup and circulating strain in community
- decide if amantadine is useful (against type A)
- restrict access to nursing home and hospitals
how to manage patients with respiratory illness
- cohorting in pediatric facility RSV and croup
- restrictive use of antiviral meds
- special care for debilatating patients
what are enteric viruses
multiply in gastrointestinal tract but do not cause gastro-enteritis
how are enteric virus able to reach other organs
viremia; dissemination in blood
how is enteric virus acquired
respiratory tract
% of enteric virus that is inapparent? % of mild illness? major illnes?
95%
4-5
1
How many types of Poliovirus
1,2,3
enteric disease, only host is humans, causes poliomyelitis, currently only found in africa and asia
polio virus
what is poliomyelitis
highly infectious, invades nervous system, paralysis within hours
how to diagnose polio
stool sample or pairing sera (acute and convalescent phase)
people inapparent infection still spread disease
two ways to fight the polio virus
killed polio virus- doesn’t produce (IgA), so can still infect community but used for immunocompromised patients and unimmunized adults
live attenuated virus- by mouth, produces IgG and IgA effective for community by suppressing virus in GI tract, don’t give to immunosuppressed or those not vaccinated against poliomyelitis
enteric virus characterized by groups A and B, seasonal variation
diagnosis:
stool sample and paired sera
no vaccine
coxsackie virus
- herpangina and hand-foot-and-mouth disease
aseptic meningitis
sign of group A coxsackie virus
minor respiratory illness
aseptic meningitis
pleurodynia, pericarditis and myocarditis
sign of group B coxsackie virus
enteric viruses
minor respiratory illness
aseptic meningitis
no vaccine
Enteric Cytopathogenic Human Orphan Disease
virus causing diarrhea
common in winter months and infants
symptoms of vomiting, diarrhea, fever, dehydration, highly infectious
incubation of 2-3 days
large number on hands, stools, dirty diapers
found in daycares
rotavirus
how is rotavirus transmitted
fecal-oral route, explosive diarrhea via aerosols and fomite
how to prevent rotavirus
quick diagnosis and isolation
hand washing
norovirus
Diagnosis, Epidemiology, transmission and prevention
Outbreaks of gastroenteritis in older children and adults
Diagnosis: first exclude bacterial cause, then
can be differentiated from bacterial gastroenteritis; electron mic and imm.
- Epidemiology: VERY CONTAGIOUS; survives
well on objects/environment
– Fecal-oral route; food-borne outbreaks and in water
- Prevention: no vaccine; handwashing and
isolation of infected individuals
respiratory virus
common in young children
gastroenteritis
diagnosed with electron mic. + imm.
fecal-oral route
adenovirus
Sporadic gastroenteritis in children and infants
electron microscopy
fecal oral route
calici and astrovirus
which two diarrhea causing viruses are very contagious
norovirus and rotavirus
5 viruses that cause a rash
- measles (German measles)
- rubella
- herpes (HSV)
- papilloma
- varicella (chicken pox)
where do rashes of measles first appear
behind ear, forehead and nostrils
2ndary complications of measels
bronchopneumonia
Encephalitis (rare)
– Exacerbation of TB and
leukemia
how to confirm measles and determine immune status
confirmation of a suspected case: by the demonstration of IgM antibody against measles in a single blood specimen or of a rising antibody titer against measles (IgG) in paired bloods.
- determination of the immune status of contacts: by the demonstration of circulating measles specific antibody (IgG).
how to prevent measels
immune globin if given within 5 day of contraction of virus
live attenuated virus at 12 months (MMR vaccine)
what happens if pregnant women is not vaccinated against rubella
may lead to birth defects
risk of damage decrease with weeks
0-4= 50% risk damage
5-8=20%
9-12=7%
birth defects of rubella (German measles)
abortion, death of newborn, cataracts (6th week), deafness (9th week), heart defect, low birth weight, dental abnormalities, mental deficiency
rash virus
common in winter and spring
school age children
epidemic every 7-10
life long immunity
birth defects for unvaccinated mother
60% of cases in 15 year olds
Rubella Virus
how to diagnose rubella
rise in IgM or Ab titer using paired sera
how to prevent rubella
check immune status of women at child bearing age
status of worker in hospital
live attenuated virus except for pregnant women
childhood
febrile illness with
characteristic rash
-Successive crops of fresh vesicles appear within 3-4 days after the onset of the rash. Papules, vesicles and crusts are present at the same time.
n non-immune adults,
occasional pneumonia,
may be fatal
Varicella
herpes zoster (shingles)
partially immune adult of varicella
pain across ONE 1 ONE nerve
found in adult
how to diagnose varicella
EM or Imm followed by culture bacteria
prevention of varicella
vaccine; detection of susceptible
persons by serological
methods; passive immunization
orally acquired herpes
cold sores
HSV 1
“herpes genitalis” associated with genital tract;
infected females can transmit to the newborn
HSV 2
can type 1 Herpes be transmitted sexually
yes
how to identify HSV
- Identification of virus particles by electron microscopy or immunological methods in clinical specimens
- The virus grows easily in cell cultures (usually within 24 - 48 hours)
- Serology of very little use
Clinical forms (apart from cold sores)
Genital infections: recurrent in both sexes
– Herpetic encephalitis: RARE (see CNS viruses)
– Neonatal Herpes: acquired during birth from
asymptomatic mother; difficult to prevent; can result in
death or severe sequelae (see CNS viruses)
– Herpetic Whitlow: affects fingers, occupational hazard
of health care workers; nosocomial infections in
neonates
– Corneal and Conjunctival Infection: can cause
ulceration of cornea and blindness
prevention of HSV (meds, mother)
antivirals; C-section
for symptomatic mothers; Vaccines coming soon
papilloma virus
Common warts on hands and feet
– Genital warts: sexual transmission, asymptomatic carriers
– Some types associated with cancer: cervix, vulva, penis
how to diagnose papilloma virus
PAP smear, immuno techniques and DNA
hybridization techniques, NO CELL CULTURE, vaccine (Gardasil)
