Enterovirus

Question 1

What is the family?

Answer 1

Picornaviridae

Question 2

What are the characteristics of Picornaviridae?

Size, enveloped?, genome, capsid features

Answer 2

Small
Non-enveloped
ssRNA (+)
4 major polypeptides on capsid

Question 3

Features of enterovirus

Answer 3

1. Stable (insensitive to detergents, survive for months at 4degrees, survive exposure to 60 degrees)
2. Replicate in GI tract
3. Prefer warm moist environments (common in tropics, epidemics in summer months)

Question 4

Route of transmisison?

Answer 4

Fecal-oral route

Question 5

What are 3 species of Enterovirus?

Answer 5

Poliovirus, coxsackievirus, echovirus

Question 6

How is enterovirus recently reclassified?

Answer 6

Based on molecular properties
- Different species: Enterovirus A-L
- Newly discovered: Enterovirus XX (XX: number)

Question 7

What does enterovirus infection lead to?

Answer 7

• Mostly asymptomatic
• Undifferentiated febrile illness
• Viral exanthema (generalised rash, HFMD, herpangia)
• Severe complications are rare (encephalitis, myelitis/lower motor neuron dysfunction/paralysis, myocarditis, aseptic meningitis)

Question 8

Discuss virus isolation as a diagnosis method

Usefulness? Which cells can?

Answer 8

• Not very useful as it is slow
• More useful for surveillance as virus takes a few days to weeks to replicate
• Coxsackie B and echovirus can be readily grown in cell culture from throat swabs, faeces, rectal swabs, CSF
• Some coxsackie A virus cannot be easily isolated in cell culture

Question 9

Discuss serology as a diagnosis method

Answer 9

• Very rarely used because of cross-reactivity
• Useful for sero-epidemiological studies

Question 10

What is used to diagnose?

Answer 10

Molecular methods (RT-PCR, genetic sequencing for typing)

Question 11

How to manage/treat?

Answer 11

Some use IVIG to treat neonatal infections or severe infections in immunocompromised individuals but efficacy is uncertain

Question 12

What is the vaccination for?

Answer 12

Poliovirus
EV71

Question 13

How many Poliovirus serotypes are there?

Answer 13

3

Question 14

What are the 2 Polio vaccines?

Answer 14

1. Intramuscular Poliovirus Vaccine (IPV)
2. Oral Poliovirus Vaccine (OPV)

Question 15

Describe the Intramuscular Poliovirus Vaccine (IPV)

Answer 15

• Consists of formalin inactivated virus of all 3 poliovirus serotypes
• Requires trained personnel to adminster
• Confers immunity (IgG) but still acts as carrier
• No risk of vaccine associated paralysis
• Vaccinates subjects only

Question 16

Describe the Oral Poliovirus Vaccine (OPV)

Answer 16

• Consists of live attenuated virus of all 3 serotypes
• Serial passage in monkey kidney cells
• No medical training required as given orally
• Life-long immunity and prevents carriage
• Small risk of vaccine associated paralysis
• Secondary vaccination

Question 17

What does Coxsackie A virus infect?

Answer 17

Mainly epithelial infections (herpangia, HFMD, conjunctivitis)
Encephalitis

Question 18

What does Coxsackie B virus infect?

Answer 18

Mainly muscular infection (Bornholm’s disease, myocarditis)
Encephalitis

Question 19

What does EV71 cause?

Answer 19

• Childhood exanthem
• HFMD indistinguishable from CA16
• Small proportion leads to CNS infection

Question 20

What viruses is HFMD commonly caused by?

Answer 20

CA16, CA6, CA24, EV71

Question 21

Is HFMD a legally notifiable disease in Singapore?

Answer 21

Yes

Question 22

What are deaths from HFMD due to in outbreaks in SEA?

Answer 22

Encephalitis, neurogenic pulmonary oedema