Human Pathogenic Viruses Overview of Diseases

Question 1

SARS-CoV-2

Answer 1

• Severe Acute Respiratory Syndrome Coronavirus 2
• virus strain that causes COVID-19
• ENVELOPED POSITIVE-SENCE ssRNA virus
• ZOONOTIC ORIGIN : passed from bats via intermediate shot to humans
• Morphology : Corona (crown) like appearance around a sphere

Question 2

COVID-19

Answer 2

• Coronavirus Disease 2019
• Symptoms : fever, cough, fatigue, shortness fo breath, LOSS OF SMALL & TASTE, loss of appetite, fatigue, sputum production, muscle & joint pains
• Complications : pneumonia, multi-organ failure, cytokine storm
• Transmission : air-borne
• Diagnostic methods :
  *Real-time Reverse Transcription Plymerase Chian Reaction (rRT-PCR) from nasopharyngeal swab sample
  (includes viral particles => viral RNA detection)
• Antigen tests (rapid tests/self tests) : viral antigen detection from nasal/nasopharyngeal swab
• Treatment :
• Anti-viral drugs
  –> REMDESIVIR (FDA & EMA) : viral RNA pol. inhibitor-nucleoside analogue
  –> MOLNUPIRAVIR (FDA & EMA) : viral RNA pol. inhibitor-nucleoside analogue
  –> NIRMATRELVIR/RITONAVIR [PAXLOVID] (EU) : Pfizer protease inhibitor
• Anti-inflammatory drugs
  –> DEXAMETHASONE : corticosteroid drug with anti-inflammatory and immunosuppressive function
• Neutralizing antibodies : mimic the immune system and attack the virus
• Vaccines
• Pfizer/Moderna : mRNA vacciens
• J&J/Astra Zeneca : vector vaccines (carry viral genes)
• Novavax : protein subunit

Question 3

Human Papilloma Virus (HPV)

Answer 3

• causes cervical cancer (HPV-16/ HPV-18) & genital warts (benign papillomas) (HPV-6/11)
• STD
• Prevention measures
• Vaccination
  –> GARDASIL (HPV 16/18/11/6)
  –> CERVARIX (HPV 16/18)
• Pap test : cervical smear

Question 4

Poliovirus

Answer 4

• causes poliomyelitis
• Prevention
• Vaccines
  –> Sabin
  –> Salk

Question 5

Mumps, Measles, Rubella viruses

Answer 5

• cause mumps, measles, and rubella respectively
• Prevention
• MMR vaccine

Question 6

Hepatitis Viruses

Answer 6

• 7 different viruses that cause hepatitis (Hep A-G)
• HEPATITIS = liver inflammation
• 2 major forms
• Acute hepatitis : JAUNDICE (characteristic symptom)
• Chronic hepatitis : can cause LIVER CIRRHOSIS & HEPATOCELLULAR CARCINOMA

Question 7

Hepatitis A Virus (HAV)

Answer 7

• RNA virus
• food borne transmission
• vaccine available

Question 8

Hepatitis B Virus (HBV)

Answer 8

• DNA virus
• STD
• vaccine available

Question 9

Hepatitis C Virus (HCV)

Answer 9

• RNA virus
• STD
• no vaccine

Question 10

Human Immunodeficiency Virus (HIV)

Answer 10

• STD (through sperm/vaginal fluids)
• Blood (infected needles…)
• Mother to child (pregnancy, birth, breast feeding)
• 2 types : HIV-1 & HIV-2
• infects the T-helper lymphocytes (Th-cells)
  –> viral glycoprotein gp 120 attaches to the CD4 receptor on the surface of Th-cells
• causes AIDS (Acquired Immunodeficiency Syndrome)

Question 11

Acquired Immunodeficiency Syndrome (AIDS)

Answer 11

• AIDS develops ~ 10-25 years after HIV infection
  –> HIV carriers are asymptomatic and can transmit the disease
  –> AIDS onset: <200 Th-cells/mm^3 of blood
• Opportunistic infections:
  –> candidiasis, toxoplasmosis, pneumonia
• Malignant tumours
  –> Kaposi sarcoma : malignant tumour of the endothelial cells fo the blood vessels
  –> Burkitt’s lymphoma : malignant tumour fo the endothelial cells of the blood vessels
• Anti-retroviral therapy increases life expectancy by 5-20 years

Question 12

HIV Diagnosis

Answer 12

• Detection : virus can be detected in blood 3-6 weeks after suspected infection date
• Window period : time between infection and detectability where virus cannot be detected yet due to low levels in blood but can still be transmitted to others
• Diagnostic Methods
  –> ELISA : detection fo anti-HIV antibodies in blood (6-8 weeks after infection)
  –> RT-PCR : detection of viral RNA in blood (3 weeks after infection)

Question 13

AIDS Therapeutic Strategies

Answer 13

• no cure for HIV infection
• no vaccine available due to high mutation rate of virus
• Treatment strategies
  –> HAART : Highly Active Anti-Retroviral Therapy
  –> Combination fo different types fo antiretroviral drugs
• common problems of antiretroviral therapy
  –> toxicity
  –> resistance

Question 14

AIDS Antiretroviral Drug Types

Answer 14

• Nucelotide analogues
  –> Inhibit viral RNA replication by being incorporated into growing cDNA chain (eg. AZT)
• Non-nucelotide analogues
  –> Inhibit activity fo reverse transcriptase (eg. Sustiva, Nevirapine)
• Protease inhibitors
  –> inhibit HIV protease which is responsible for the viral polypeptide cleavage and hence the maturation of the new virus particles (eg. saquinavir, ritonavir)

Question 15

Mad Cow Disease

Answer 15

• Prion
• Infects cattle
• transmitted to humans by consumption of contaminated beed (cooking does not destroy prions)
• causes Creutzfeldt-Jacob disease (CJD) in humans

Question 16

Creutzfeldt-Jacob Disease (CJD)

Answer 16

• fatal CNS infection by prions
• Symptoms: ataxia, memory loss, convulsions, coma