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
17. DNA viruses
Double – stranded
•Adenoviridae
•Herpesviridae
•Poxviridae
•Papovaviridae
•Hepadnaviridae
Single – stranded
oParvoridae
MIC208 - VIROLOGY 17
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
