AuCoin 3: + strand non-enveloped viruses Flashcards
What are TWO non-enveloped + strand RNA viruses?
picornaviruses
calici
What are the three subclasses of picornaviruses?
enterovirus
rhinovirus
hepernavirus
Describe the genetic structure of the picornaviruses.
naked virion
small
icosahedral capsid
ssRNA genome
Which type of picornavirus is resistant to pH 3-9, detergents, sewage treatment and heat?
enteroviruses
ex: poliovirus, coxsackie A and B, echovirus, enterovirus
The genome of picornaviruses is (blank), which infers that it could be infectious without its capsid; the genome replicates in the (blank); the viral genome produces (blank)
mRNA; cytoplasm; polyproteins
What enzyme is essential for replication of RNA viruses in the cytoplasm?
RNA-dependent RNA polymerase
Do + sense RNA viruses need RNA-dependent RNA included in the virion?
no - they are mRNA, but RNA dependent RNA polymerase makes - strand RNA as a template for more + strand RNA
How are picornaviruses, like enterovirus and poliovirus, transmitted?
fecal-oral route
What % of picornaviruses are clinically apparent?
1%
Where does initial replication occur for the picornaviruses?
in the oropharynx and small intestine, leading to nausea and vomiting
What can the poliovirus cause?
disease ranges from asymptomatic to paralytic poliomyelitis, which is an acute viral infection of the meninges and the motor neurons of the spinal cord and brainstem
What clinical clues would cause you to expect a case of paralytic poliomyelitis?
individual has acute onset of flaccid paralysis
stool sample or swab of pharynx with poliovirus
In what countries is poliovirus still endemic in? Is it seen in the Western hemisphere?
Nigeria, Pakistan, Afghanistan; eradicated from the Western hemisphere
What do enteroviruses cause?
viral meningitis
Which is worse, viral or bacterial meningitis?
bacterial
Who gets viral meningitis? How do they get it?
younger children less than 5yo; changing a diaper or not properly washing their hands after fecal contact
What clues would tell you that a patient has viral meningitis?
sudden onset of fever, headache, stiff neck; accompanied by nausea, vomiting, photophobia, altered mental status
**symptoms last 7-10 days and then the patient usu recovers
If meningitis is expected, what should you obtain from the lab?
CSF sample and a blood sample
Coxsackie viruses are non-polio enteroviruses. What are the two flavors, and what does each cause?
Group A causes herpangina - ulcers in oropharynx, fever, sore throat (hand-foot-and-mouth-disease) and Group B causes pleurodynia - fever, pleuritic chest pain, myocarditis
Groups A and B Coxsackie viruses can cause what condition?
aseptic meningitis
mild paralysis
Who usually gets Coxsackie viral infections? How do you diagnose it?
young people with naive immune systems; diagnosed by PCR of enteroviral RNA in spinal fluid
The echovirus (ECHO = enteric cytopathic human orphan) is another type of non-polio enterovirus. How is this virus transmitted?
fecal-oral route, transmitted in pools
What do echoviruses cause?
aseptic viral meningitis upper respiratory tract infection febrile illness infantile diarrhea hemorrhagic conjunctivitis hand foot and mouth disease
How do you diagnose echovirus?
PCR
This virus is the main cause of the common cold; there are over 100 serological types; transmitted by aerosolized droplets or fomites
rhinovirus
How do you get infected with rhinovirus? What does it infect?
through the upper respiratory tract; infects nose rather than lower resp tract
How would you know if someone had the rhinovirus?
after 2-4 days of incubation, they will be sneezing w nasal discharge, sore throat, cough, headache (usu no fever or aches)
**illness lasts about 1 week
Fever and extreme exhaustion are not usually seen with rhinovirus infection. What are these more commonly symptoms of?
influenza infection
What does the Heparnavirus cause?
Hep A
What is the heparnavirus also known as? How is it transmitted?
enterovirus 72; one serotype; transmitted by fecal-oral route in areas of poor sanitation and poor hygiene - infection occurs from fecally contaminated water and food
What are the clinical symptoms of heparnavirus infection?
fatigue fever nausea vomiting JAUNDICE dark urine, pale feces elevated liver enzymes
- *may be asymptomatic, mild illness, or debilitating illness
- *15-50 day incubation period
How do you diagnose heparnavirus?
IgM antibodies or 4-fold rise in IgG 1-3 weeks after infection
How do you recover from heparnavirus?
usu just resolves in 2-4 weeks, no chronic infection
What vaccine would you recommend for people who travel?
heparnavirus!
**international travel is considered the number one risk factor for HAV infection in the US
Everything discussed so far was PICOrna viruses. Now onto CALICviruses. What is the main pathogen in the calicivirus family?
Norovirus - Norwalk virus
How is Norwalk virus transmitted? What do people usually ingest that causes infection?
fecal-oral route; contaminated seafood or water (on cruiseships, in pools)
What are the symptoms of Norwalk virus?
most common cause of viral gastroenteritis in older children and adults in the US sudden onset of vomiting diarrhea (non-bloody) low grade fever abdominal cramping
**short incubation period (24hrs)
How do you diagnose Norwalk virus infection?
clinically
can use PCR on stool
