This document discusses types of viral infections including acute, persistent, chronic, and slow infections. It describes portals of entry and exit for viruses in the body. The main routes of viral transmission are discussed as droplet, airborne, common vehicle, vector-borne, and contact. Various sources and modes of person-to-person viral transmission are outlined. Important viral diseases causing illness in humans are listed. Finally, RNA and DNA viruses are categorized based on their genome type and structure.

1. Identification of virus
Prepared by:
Putri Shareen Binti Rosman

2. Types of viral infection
Acute infections
-relatively short duration with rapid discovery.
Most viruses that infect humans, such as those
that cause routine respiratory infections (e.g.,
cold viruses, influenza viruses) and
gastrointestinal infections (e.g., Rotaviruses,
Noroviruses),skin infection(e.g.,Varicella zoster
virus) cause acute infections.

3. Types of viral infections
Persistent infections
- Viruses continually present in the body.
- Late complications following acute infections. Also
known as latent infection.
Eg:HSV-1(fever blister),HSV-2(genital herpes).
 Chronic infection
- the virus can be demonstrated in the body at all
times and the disease may be present or absent for
an extended period of time.
- Eg: hepatitis B (caused by HBV) and hepatitis C
(caused by HCV).

4. Slow infections
- are ones in which the infectious agents gradually
increase in number over a very long period of time
during which no significant symptoms are seen.
- Eg: include AIDS (caused by HIV-1 and HIV-2)
and certain lentiviruses that cause tumors in
animals.

5. Portals of entry and exit of
viruses
Virus can enter into our body at many different
sites and these are called portals of entry.
Respiratory Tract
Genitourinary Tract
Gastrointestinal Tract
Skin/Mucous Membrane
Transplacental (mother to fetus)
Blood

6. Modes of Transmission
The mechanism for transfer of an
infectious agent from a reservoir to a
susceptible host.
Dr.M.ElBashaar

7. Means of Transmission
Five Main Routes
Droplet
Airborne
Common Vehicle (Food, blood)
Vector-borne
Contact
Direct Contact
Indirect Contact (Objects)
Dr.M.ElBashaar

8. Sources and modes of
transmission of infection
1. Person-to-Person Spread
 Skin-to-skin contact, clothes, (viral as HSV1)
 Droplets during coughing, sneezing (common
cold, flu, swine flu, smallpox,measles,SARS)
 Stool-to-mouth (fecal-oral) spread, usually via
dirty hands or utensils (hepatitis A,poliomyelitis)
Dr.M.ElBashaar

9. Sources and modes of transmission of
infection
Sexually transmitted (gonorrhea, genital HSV2,
genital warts (human papillomavirus – HPV).
Blood-to-blood contact by:
contaminated needles, usually by drug addicts or health
workers (hepatitis B, C, AIDS)
blood transfusion (hepatitis B,C, AIDS, viral hemorrhagic
fevers)
Vectors: rabies anthropod:mosquitoes (Malaria,
Dengue,Yellow fever)
Dr.M.ElBashaar

10. Sources and modes of transmission of infection
Spread from mother to fetus during pregnancy
(hepatitis B, C, HIV, HSV-1, HSV-2, rubella, varicella,
bird flu).
Food poisoning is an infection of the gastrointestinal
tract caused by microbes from contaminated food:Eg:
Enterovirus
Dr.M.ElBashaar

11. Viral Diseases
Diseases caused by viruses has been known for
thousand years ago.
Antibiotics are not effective in killing viruses
Certain viruses are also linked to cancer in human
such as Hepatitis B (liver cancer),Epstein-Barr
virus (Burkitt’s Lymphoma) and Human
Papilomavirus (cervical cancer).

12. Important viral diseases
AIDS:Immune system failure
Common cold:Sinus congestion
Ebola:High fever,uncontrolled bleeding
Hepatitis A:Flu like symptom,swollen liver
Hepatitis B:Flu-like symptom,swollen liver.
Influenza (flu):Fever,chills,sneezing,body aches.
Mumps:Painful swelling of saliva glands
Polio:Fever,headachenstiff neck,paralysis
Rabies: Mental depression,madness,paralysis

13. SARS:High fever,headche,dry cough,death.
Smallpox:Malaise,fever,blisters,blindness
Yellow fever:Fever,weakness,yelllow skin.

15. RNA viruses (+ve sense)
Picornaviridae
Togaviridae
Flaviviridae
Retroviridae
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16. RNA viruses (-ve sense)
Paramyxoviridae
Rhabdoviridae
Orthomyxoviridae
Filoviridae
Bunyaviridae
Reoviridae (double-stranded)
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17. DNA viruses
Double – stranded
•Adenoviridae
•Herpesviridae
•Poxviridae
•Papovaviridae
•Hepadnaviridae
Single – stranded
oParvoridae
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18. Assignment 1
Per group have 4-5 per group = 16 groups
Presentation after CNY holiday
Each group have 5 minutes for presentation
Represent 5% marks for assessment
Explain the genome content, viral morphology,
modes of transmission, infection in
human,treatment.
MIC208 - VIROLOGY 18