1. VIRUSES AND DISEASES Omilabu S.A, Ph.D Professor and Consultant Virologist Department of Medical Microbiology and Parasitology, CMUL.

2. VIRUSES AND DISEASES Overview – Most infections are asymptomatic or benign – Others may produce overt disease – Severity depends on the nature of the virus and organ involved Common sites are; – Respiratory & gastrointestinal tracts – Central nervous system – Other sites are, Skin, Mouth, Eye, Liver & other organs

3. DISEASES OF THE RESPIRATORY SYSTEM Tract through which many viruses enter the host. Nature depends on whether the viruses colonize the upper or lower respiratory tract. Diseases of the upper respiratory tract are generally benign, which includes; – Common cold (Rhinoviruses, Influenza viruses, Adenoviruses, Coronaviruses) – Pharyngitis (Adenoviruses, Herpes simplex virus, Coxsackievirus, Lassa fever virus, Cytomegalovirus) – Laryngitis.

4. Common Cold – Transmission by inhalation – Clinical features: Nasal stuffiness, sneezing, running nose, sore throat, chills cough etc – No laboratory diagnosis is usually required – No specific treatment, except influenza (amantadine or rimatandine) Pharyngitis – Transmission by direct contact and aerosol – Clinical features: sore throat, nasal symptoms or conjunctivitis – No laboratory diagnosis is usually required, except in Epstein Barr or Cytomegalovirus infections diagnosed by serology and viral isolation

5. Diseases of the lower respiratory tract are often severe, which includes; – Viral Croup (Parainfluenza virus, Influenza viruses, Respiartory syncytial virus). – Tracheitis and Tracheobronchitis (Parainfluenza virus, Influenza viruses, Herpes simplex virus). – Bronchiolitis (Respiartory syncytial virus, Parainfluenza virus). – pneumonia (Respiartory syncytial virus, Parainfluenza virus, Influenza viruses Adenoviruses, Cytomegalovirus, Coronavirus, SARS virus, Varicella- zoster virus, Measles).

6. Viral croup – Also known as laryngotracheobronchitis. – Primarily affects children under 3 years. – Transmission by inhalation. – Clinical features: cough which progresses into barking cough, fever may be present. – Self limiting disease lasting 3-4 days. – Diagnosis: virus isolation, serology and immunofluorescence on epithelial cells in respiratory secretions. – Treatment is with antibiotics if complicated by bacterial infections.

7. Tracheitis – Inflammation of the trachea. Tracheobronchitis – Inflammation of the trachea and bronchi. Transmitted by inhalation Symptoms include fever, headache, myalagia, malaise, anorexia and non-productive paroxysmal cough. Diagnosis by isolation and serology.

8. Bronchiolitis – Inflammation of bronchioles. – Disease of children and infants. – Characterized by an obstruction of airflow. Transmitted by inhalation. Symptoms are rhinitis, nasal congestion and discharge, difficulty in breathing and wheezing. Diagnosis by isolation and serology. Treatment with Ribavirin in aerosol form used for Respiratory syncytial virus infection.

9. Pneumonia – Major cause of morbidity in children. – Inflammation of the lung tissue. Transmitted by inhalation. Symptoms are nonproductive cough, wheezing, difficulty in breathing and cyanosis.

10. Viral Diseases of the CNS Spread to the CNS occurs through the blood stream, nerves or macrophages The major diseases resulting are: Aseptic Meningitis- inflammation and swelling of the meninges of the brain & spinal cord Self limiting Etiology: Enteroviruses, mumps virus, HIV, HSV 1

11. Viral Diseases of the CNS Symtoms are non-specific (fever, headache, nausea & vomiting) Diagnosis by viral isolation and antibody detection Acyclovir can be use for HSV infection

12. Acute Encephalitis: inflammation of the brain tissue Aetiology: rabies virus, arboviruses, HSV 1, polio virus Symptoms includes fever, headache, altered level of consciousness & cognition, focal neurological defects Diagnosis: Antigen & antibody detection, viral isoltaion from brain biopsy

13. Post infectious encephalitis: acute demyelinating disease caused by immunopathological reaction Associated with measles, mumps, influenza, rubella & varicella viruses

14. Spongiform Encephalopathies: Degenerative diseases of the CNS Caused by prions, characterized by long incubation periods & slow virus replication, E.g Kuru

15. Viral Diseases of the Gastrointestinal tract Oral Disease – Herpes simplex – gingivostomatitis (herpes labialis). – Epstein Barr – oropharyngeal disease. – Measles viruses – koplik spots. Gastroentiritis (Rotavirus, Adenovirus 40 & 41, Caliciviruses & Astroviruses.) – Occurs as childhood diarrhoea. – Symptoms are watery stool, vomiting, dehydration etc – Diagnosis by antigen detection in stool and serology – Treatment is by fluid replacement therapy.

16. Viral Diseases of the Skin Maculopapular Rash: Measles virus, Rubella virus, Arboviruses, Human parpovavirus B19, Echovirus 16, Epstein Barr virus, CMV, Human herpesvirus 6. Vesicles: HSV, VZV, Vesicular stomatitis virus, Coxsackie A virus, Poxvirus Papillomas (Warts): Papillomavirus. Nodules: Molluscum contagiosum virus.

17. Viral Diseases of the Eye Conjunctivitis (Measles, Adenovirus & Herpesvirus) – Transmitted by direct contact with infected secretions. – Symptoms are hyperaemia, watery discharge, lid mattering. Keratitis (Herpes simplex virus, VZV, Adenovirus, Measles, Mumps and Rubella viruses) – Symptoms are severe pain, photophobia, lacrimation impairment of vision etc.

18. Viral Diseases of the Liver Viral Hepatitis – Infection of the liver hepatocytes 6 known types of Hepatitis Virus 5 RNA Viruses (HAV, HCV, HDV, HEV, & HGV) 1 DNA Virus (HBV)

19. HAV & HEV are transmitted via fecal-oral route All others are transmitted via blood to blood contact It could be a sudden illness with a mild to severe course followed by complete resolution (acute viral hepatitis) It could have a prolonged course of active disease or silent asymptomatic infection (chronic viral hepatitis)

20. Viral Diseases of the Heart Myocarditis – Inflammation of the myocardium. – Several viruses involved. – Coxsackie B virus most important, others are Epstein Barr virus & CMV. – Adenoviruses implicated in peadiatric cases. – Symptoms include chest pain, palpitation, flu-like or respiratory illness etc. Pericarditis – Inflammation of the pericardium. – Enteroviruses are mostly implicated. – Others are Coxsackie A & B, Echovirus, Influenza viruses, CMV.

21. Viral Haemorrhagic Fevers Major public health problem in many parts of the world (Africa). African Haemorrhagic Fevers e.g Yellow fever, Crimean-Congo haemorrhagic fever, Rift Valley fever, Lassa fever, Marbourg & Ebola fever. Dengue Haemorrhagic fever occurs primarily in South East Asia.

22. Sexually Transmitted Diseases Most important are; – Genital herpes: caused primarily by HSV 2 but also HSV 1. – Genital warts: caused by HPV 6, HPV 11, HPV 16 & HPV 18. Several others viruses are shed in the genital secretions but cause no disease in the genital tract, e.g HIV-1, HIV-2, HBV, HCV, HSV, CMV.