Picornaviridae Flashcards
What are the morphologic features of Picornaviridae?
- Single-stranded positive-sense non-enveloped RNA viruses
- Smallest RNA viruses
What are the genera included under Picornaviridae?
- Rhinoviruses
- Enteroviruses
What are the groups of rhinoviruses?
Group A, group B, group C
What are the receptors that rhinoviruses bind to?
- Intercellular adhesion molecule-1 (ICAM-1)
- Low-density lipoprotein receptor (LDLR)
How are rhinoviruses transmitted?
- Hand to hand
- Hand to eye
- Hand–object–hand (fomites)
Why can rhinoviruses not be transmitted through food?
They are acid labile; complete inactivation occurs at pH 3.0
What are the clinical features of infection with rhinoviruses?
Asymptomatic or upper respiratory tract infection (common cold; coryza; rhinosinusitis), with symptoms:
- Chilliness
- Runny nose
- Sore throat
- Coughing
- Sneezing
- Nasal congestion
- Headache
- Low-grade fever
- Fatigue and malaise
- Exacerbation of the symtpoms of acute asthma or COPD
What is the course of infection with rhinoviruses?
- Short incubation period of 2–4 days
- Illness lasts about 7 days
How are rhinoviruses diagnosed?
Real-time PCR
How are rhinoviruses treated?
Symptomatic treated
Are there vaccines for rhinoviruses?
No
Why is immunity to rhinoviruses so short lived?
There are more than 150 types
What is the seasonality of rhinovirus infection?
Common in fall, winter, and spring
What are the viruses included in the genus Enterovirus?
- Poliovirus
- Coxsackieviruses A and B
- Echoviruses
- Enteroviruses
- Parechoviruses
How many types of poliovirus are there?
Three antigenic types
How is poliovirus transmitted?
- Mouth is the portal of entry
- Primary replication takes place in the oropharynx or intestine
- Poor hygiene and sanitation is linked to spread of the virus by the fecal–oral route
What are the features of infection with poliovirus?
- Asymptomatic infection in 90–99% of cases
- Acute febrile illness (the most common clinical picture): fever, headache, nausea, vomiting, constipation, sore throat
- Nonparalytic poliomyelitis (aseptic meningitis): stiffness and pain in the back nad neck with rapid and complete recovery
- Paralytic poliomyelitis: flaccid paralysis resulting from lower motor neuron damage and subsequent muscle atrophy. Fatality in 5–10% of cases due to respiratory failure by depression of the respiratory centers
How does poliovirus spread throughout the nervous system?
It spreads along the axons of peripheral nerves to the CNS, where it continues to progress along fibers of lower motor neurons to increasingly involve the spinal cord or the brain
How is poliovirus diagnosed?
- Virus culture
- PCR
Are there vaccines for poliovirus?
- Oral polio virus (OPV, Sabin vaccine; live attenuated): has higher efficacy but may rarely cause poliomyelitis
- Inactivated polio virus (IPV, Salk vaccine): has lower efficacy but is safer
Is immunity to poliovirus observed after infection?
Yes, and this immunity is permanent for that antigenic type. Cross-protection is observed between types
There have been many efforts to eradicate poliovirus after the eradication of smallpox, yet these attempts have all failed. Why is this?
There is a high rate of asymptomatic disease and transmission, leading to undiscovered carriers and an unbreakable chain of infection
What are the diseases caused by coxsackieviruses A and B?
- Aseptic meningitis: full recovery in most patients
- Herpangina (caused by group A): fever and sore throat with discrete vesicles on the posterior half of the palate, pharynx, tonsils, or tongue. Frequent in small children. Self-limited
- Acute febrile illness with or without skin rash: frequent during summer
- Common cold
- Hand-foot-and-mouth disease (caused by group A and enterovirus): oral and pharyngeal ulcerations and a vesicular rash of the palms and soles that may spread to the arms and legs. Self-limited
- Pleurodynia (epidemic myalgia; caused by group B): fever and stabbing chest pain. Self-limited
- Myocarditis: acute inflammation of the heart or pericardium. May be fatal
Which diseases are caused by coxsackievirus A only?
- Herpangina
- Hand-foot-and-mouth disease
Which diseases are caused by coxsackievirus B only?
Pleurodynia
What are the diseases caused by echovirus, enterovirus, and parechovirus?
- Aseptic meningitis
- Encephalitis
- Febrile illnesses with or without rash
- Common cold
- Acute hemorrhagic conjuncitivitis
Are there vaccines for echovirus, enterovirus, and parechovirus?
No
How are echovirus, enterovirus, and parechovirus diagnosed?
Real-time PCR
