Picornaviruses

Picornaviruses Small (pico) RNA Naked capsid >230 members 5 genera

Picornaviruses 5 genera

EnterovirusEnterovirus RhinovirusRhinovirus HeparnavirusHeparnavirusCardiovirusCardiovirus AphtovirusAphtovirus

Picornaviruses EnterovirusesAt least 72 serotypes

Polioviruses Coxsackieviruses Echoviruses

International Virus Taxonomi committee Enterovirus genus (EV):

Poliovirus and EV A, B, C and D.

Parechovirus cinsi (PeV): echovirus 22 ve 23

Picornaviruses Enteroviruses (EV)At least 72 serotypes

Polioviruses Coxsackieviruses Echoviruses

Human parechoviruses 1-3 (HPeV)

Picornaviridae Enterovirus

Poliovirus type 1, 2, and 3 Coxsackie A virus types 1 to 22 and 24 Coxsackie B virus types 1 to 6 Echovirus (ECHO virus) types 1 to 9, 11 to 27, and 29 to 34 Enterovirus 68 to 71

Rhinovirus types 1 to 100+ Cardiovirus Aphtovirus Heparnavirus

HAV

Picornaviruses Enteroviruses

Capsid very resistant facilitates transmission by the fecal-oral route

Infection initiated in the gastrointestinal tract “Rarely cause enteric disease” Infections are usually asymptomatic

Picornaviruses/Replication The specifity of the picornavirus interaction

for cellular receptors is the major determinant of the target tissue tropism and disease

VP1 and “canyon” 80% of rhinoviruses and several serotypes of

of coxsackieviruses recognize ICAM-1 polio a different molecule

Enteroviruses/Pathogenesis&Immunity The diseases produced by the enteroviruses

are determined mainly by differences in tissue tropism and cytolytic capacity of the virus

Poliovirus with the narrowest tissue tropismrecognize a receptor expressed on anterior horn cells of the spinal cord, dorsal root ganglia, motor neurons, skeletal muscle cells, and few other cells

Enteroviruses/Pathogenesis&Immunity Portal of entry:

URT Oropharynx Intestinal tract

Most enteroviruses are cytolytic Excp: HAV

Viral shedding From oropharynx From the intestine (> 30 days)

Enteroviruses/Pathogenesis&Immunity “Antibody is the major protective immune

response to the enteroviruses”

Enteroviruses/Epidemiology “The enteroviruses are exclusively human

pathogenes” Spread by the fecal-oral route Asymptomatic shedding can occur

Poor sanitation and crowded living conditions foster transmission of the viruses

Enterovirus epidemics sewage contamination of water supplies

Outbreaks in schools & day care centers (summer) Spread via resp. tract coxsackie & echov.

Enteroviruses/Epidemiology Poliovirus has been eliminated from the Western

Hemisphere, but “not from the worldnot from the world” Polio cause more severe disease in late

childhood, the adolescent years, or adulthood Coxsackie A mor severe in adults than

children Coxsackie B & some echo“s” can be particularly

harmful to infants

Enteroviruses/Clinical syndromes Poliovirus infections

Asymptomatic illness (90%) Abortive poliomyelitis (minor illness)

Nonspecific febrile illness (5%) Nonparalytic poliomyelitis or aseptic meningitis

1 to 2%, symptomes of the minor illness + CNS sm Paralytic polio, the major illness

0.1 to 2.0%

Enteroviruses/Clinical syndromes Poliovirus infections

Paralytic poliomyelitis Asymmetrical flaccid paralysis with no sensory loss Poliovirus type 1 is responsible for 85% of cases Vaccine-associated disease (reversion of type 2&3) Recovery, within 6 months to 2 years

Bulbar poliomyelitis More severe, 75% death, iron lungs (1950’s) Postpolio syndrome (30-40 years later) in 20-

80% of the original victims)

Enteroviruses/Clinical syndromesCoxsackievirus and echovirus infections Herpangina

Several types of Coxsackie A Hand-foot-and-mouth disease ( a vesicular exanthem)

Usually caused by coxsackievirus A16 Pleurodynia (Bornholm’s disease)(Devil’s grip)

Fever + unilateral low thoracic, pleuritic chest pain

Coxsackie B

Enteroviruses/Clinical syndromesCoxsackievirus and echovirus infections Myocardial and pericardial infections*

Coxsackie B Occur sporadically in older children and adults Most threatening in newborns Febrile illness, sudden unexplained onset of

heart failure high mortality

Enteroviruses/Clinical syndromesCoxsackievirus and echovirus infections Viral (aseptic meningitis)*

Acute febrile illness + CNS symptoms Petechia or a rash Summer and autumn outbreaks with Echo 11

Fever, rash and common cold-like symptoms Other diseases

Acute hemorrhagic conjunctivitis Enterovirus 70 and coxsackie A24

Enteroviruses/Clinical syndromesCoxsackievirus and echovirus infections Other diseases

Acute hemorrhagic conjunctivitis Enterovirus 70 and coxsackie A24

transplacental infection Insulin-dependent diabetes

Coxsackie B

PeV

Respiratory infections Gastrointestinal infections

Enteroviruses/Laboratory Diagnosis Nükleic acit detection Isolation Serology: Antibody

Enteroviruses/Treatment Pleconaril new antiviral drug

Enteroviruses/ Prevention & control“The prevention of paralytic polyomyelitis is one

of the triumphs of modern medicine”Poliovirus vaccines:1. IPV, developed by Jonas Salk2. OPV, developed by Albert Sabin (live

attenuated)

'Poliosuz Ülke Sertifikası’

Rutin aşılama çalışmalarına ek olarak Ulusal Aşı Günleri (UAG) ve Mop-up gibi destek aşılamalar düzenlemesi gerekmiştir.

1998 yılında tip 1 poliovirüse bağlı son çocuk felci vakası Ağrı ilinde saptanmıştır.

Bu vaka aynı zamanda DSÖ Avrupa bölgesi’nin de son polio vakası olmuştur.

Türkiye, Dünya Sağlık Örgütü Avrupa bölgesi ile birlikte 21 haziran 2002 tarihinde çocuk felci hastalığından (polio) arındırılmış olarak sertifikalandırılmıştır.

Iron lung

Polio sekeli

Rhinoviruses Most important cause of the common cold

and URTI ICAM-1 Unable to replicate in the GIT Labile to “ pH” Grow best @ 33oC Infection can be initiated by as little as 1

(one) infectious viral particle “Runny nose”

Rhinoviruses Most important cause of URTI ~ 50% Common cold:

Enteroviruses Coronaviruses Adenoviruses Parainfluenza viruses

Rhinoviruses Common cold symptoms

Sneezing Rhinorrhea nasal obstruction Mild sore throat Headache Malaise Cough Fever & rigors

Rhinoviruses The clinical syndrome of the common cold

is usually so characteristic that laboratory diagnosis is unnecessary!!