PICORNAVIRUS (Enterovirus & Rhinovirus)

Picornavirus

• Represent a very large virus family with respect to the number of members but one of the smallest in terms of virion size & genetic complexity

• Includes two major groups of human pathogens: Enteroviruses and Rhinoviruses

• Also known as the “foot and mouth disease virus”

Properties of Picornaviruses• Icosahedral, 28-30 nm in diameter, contains 60 subunits each of

four proteins

• Composed of RNA (30%), Protein (70%)

• No envelope

• Made up of many enterovirus and rhinovirus types that infect humans and lower animals causing various illnesses ranging from poliomyelitis to aseptic meningitis to the common cold

• Replication occurs in the cytoplasm

Enterovirus

• A genus of positive-sense, single-stranded RNA viruses associated with several human and mammalian diseases

• Often found in respiratory secretions and stool of an infected person

Enteroviruses

• Poliovirus

• Coxsackievirus

• Echovirus

Poliovirus

• Affects the motor neurons of the spinal cord resulting in flaccid paralysis

• Most are subclinical• Affects the CNS in serious forms

Characteristics of Poliovirus

• Inactivated at 55˚C for 30 minutes

• Purified form is inactivated by chlorine

• Unaffected by ether or sodium deoxycholate

• Incubation period of 7-14 days but may range to 3-35 days

Transmission of Poliovirus

• Ingestion

• The mouth is the portal of entry and multiplication takes place in the oropharynx or intestine

Symptoms of Poliovirus

• Includes fever, malaise, drowsiness, headache, nausea, vomiting, constipation & sore throat

• Muscle Atrophy• Paralytic Polimyelitis • Nonparalytic Poliomyelitis -stiffness and pain in back and neck for 2-10 days

Specimen: Stool Samples

Treatment: No known cure

Coxsackievirus

• One of the leading causes of aseptic meningitis

• Causes paralysis but since it is incomplete, it is reversible

• Has two types: Group A and Group B Coxsackievirus

• Both groups A and B cause nonspecific febrile illness, rashes, upper respiratory tract disease and aseptic meningitis

Group A Coxsackievirus

• Tend to infect the skin and mucous membranes

• Causes Herpangina, acute hemorrhagic conjunctivitis and hand-foot-mouth disease

Group B Coxsackievirus

• Tend to infect the heart, pleura, pancreas and liver

• Causes pleurodynia, myocarditis, pericarditis, and hepatitis

Characteristics of Coxsackievirus

• Incubation period of 2-9 days

• Found in the throat for a few days early in the infection

• Found in stool for up to 5-6 weeks

• Shares many characteristics with poliovirus

Transmission of Coxsackievirus

• Ingestion

• Fecal-oral route

Symptoms of Coxsackievirus

• Fever, Nausea, Flu-like symptoms

• Sore throat

• Rashes on hands, mouth and feet

Specimen: Throat Swabs, Rectal Swabs, Nasopharyngeal Swabs, Stool, CSF

Treatment: No specific treatment other than those that will provide relief for pain

Echovirus

• Enteric Cytopathogenic Human Orphan (ECHO) Virus

• Infects the human enteric tract

• Highly infectious with children as the primary target

Characteristics of Echovirus

• Measures 24-30 nm

• Virus may spread to the CNS, liver, spleen, bone marrow, heart and lungs

• Air-borne

• Most common cause of Aseptic meningitis

Transmission of Echovirus

• Person-to-person contact

• Fecal-oral route

• Saliva

• Intake of contaminated water or food

Symptoms of Echovirus

• Liver Failure

• Myocarditis

• Mild nonspecific illness with low fever

• Rashes on face, neck, upper extremities and chest

Specimen: Stool, CSF, Body fluids, Tissues manifesting lesions

Treatment: No specific treatment since care is directed at relief of symptoms

Rhinovirus

• Common cold viruses

• Commonly recovered from people with mild upper respiratory illnesses

• Responsible for about ½ of asthma exacerbations

Characteristics of Rhinovirus

• Acid-labile• Occurs primarily in the nose• Most common viral infective agents in humans • More thermostable than enteroviruses and

may survive for hours on environmental surfaces

Transmission of Rhinovirus

• Aerosols of respiratory droplets and contaminated surfaces

• Direct person-to-person contact

Symptoms of Rhinovirus

• Sore throat• Runny nose• Nasal congestion• Sneezing• Cough• Fatigue• Loss of appetite

Specimen: Nasopharyngeal Swab

Treatment: No treatment