Cell: the smallest unit of living structure capable of independent existence, composed of a membrane-enclosed mass of protoplasm containing a nucleus or nucleoid (cell membrane, cytoplasm, nucleus, golgi apparatus, mitochondrion, lysosome...), Genetic information (blueprint) stored as DNA in the nucleus>copy (RNA)>factory: cellular machinery to produce proteins and DNA/RNA in the cytoplasm

Virus is DNA or RNA in the capsid or in the capsid in the envelope. No machinery to produce their own proteins

Enter cell via cell membrane receptor (e.g. HIV:CD4, rabies: acetylcholine receptor) & replicate, then release either by cytolysis or budding (forming envelope)

Retrovirus is different: genetic information integrated into host-genome (compose 5-8% of human genome)

  • Non-enveloped: DNA: adenovirus, RNA: HAV, poliovirus, rotavirus, norovirus

  • Enveloped: surrounded by lipid, easily destroyed... difference how to handle

Genome structure: large vs. small; segmented vs. non-segmented

Antigenic shift (abrupt, major change in the virus) vs. antgenic drift (small changes that happen continually over time as the virus replicates)


  • Flaviviridae, flavivirus. Enveloped and spherical with 30nm core. ssRNA virus

Transmission routes

  • Oral: Picornaviridae (poliovirus, HAV, enterovirus); Caliciviridae (noroviruses)

  • Direct skin contact: filoviridae (ebola)

  • Droplet: picornaviridae (rhino), coronaviridae (SARS, MERS), orthomyxoviridae (influenza), paramyxoviridae (measles, mumps, parainfluenza, RSV)

  • Direct inoculation*: togaviridae (CHIKV); flaviridae (YF, DENV, WNF, JE, Zika); bunyaviridae (Crimean-Congo HF, SFTS)

  • Sexual transmission: hepadnaviridae (HBV), papovaviridae (HPV), herpesviridae (HSV); retroviridae (HIV, HTLV)


Viral encephalitis

  • Flaviriviridae, Flavivirus: JE, dengue, St. Louis, West Nile, Murray Valley, Tick-borne

  • Togaviridae, Alphavirus: ...

Viral hepatitis

  • Hepatitis A, B, C, E


  • RSV, influenza

Viral diarrhoea

  • Rotavirus, norovirus

Viral haemorrhagic fever (4 families, all RNA viruses...)

  • Arenaviridae: Lassa,

  • Filiviridae: Ebola,

  • Bunyaviridae

  • Flaviviridae: YF...

Virus + rash

  • Infectious mononucleosis, CMV

  • Measles, rubella

  • Dengue, CHIK, Zika

  • HIV

  • Viral haemorrhagic fever

Virus and cancer

Virus transforms the host cell by interfering with normal cellular regulation, resulting in the development of a cancer cell. This may be the result of the activity of viral or cellular oncogenes

  • Hep B/C: HCC

  • EBV: Burkitt's lymphoma, B-cell lymphoma, nasopharyngeal carcinoma

  • Herpes virus (HHV8): Kaposi's sarcoma, primary effusion lymphoma

  • HPV: cervical, anal, oral carcinoma

  • Human T-cell leukaemia lymphoma virus: adult T-cell leukaemia/lymphoma

  • HTLV-1


  • Detect the virus: culture isolation, antigen detection, viral nucleic acid (DNA/RNA) detection e.g. PCR, LAMP

  • Detection of specific immune response: antibodies


Anti-viral drugs: limited number of virus-specific targets