This document discusses the epidemiological features and modes of transmission of HIV. It describes the virus itself, including that it is an enveloped retrovirus with two RNA strands. It spreads primarily through sexual contact, blood transfusions, needle sharing, and from mother to child. The incubation period from infection to AIDS symptoms is highly variable, ranging from less than a year to over 15 years. Key host factors are age 20-49 years and belonging to high-risk groups like men who have sex with men.

1. EPIDEMIOLOGICAL FEATURES
AND
MODES OF TRANSMISSION OF HIV
Somu Venkatesh
Roll 118

2. Contents
☻Agent factors
☻Host factors
☻ Modes of transmission
☻ Replication
☻ Incubation Period

3. Agent factors
Agent:
• Human Immunodeficiency Virus (HIV)
• There are HIV-1 and HIV-2
• HIV-1 is grouped into M,N and O. M group
has subtypes A,B,C,D,F,G,H and J
• HIV-2 is grouped into HIV-2A and HIV-2B

4. Characteristics of the virus
• Icosahedral (20 sided), enveloped virus of the
lentivirus subfamily of retroviruses.
• Retroviruses transcribe RNA to DNA.
• Two viral strands of RNA (diploid + ssRNA)
present in core.
• Structure - envelope, shell, core

6. Genes
• Three main structural genes:
–Group Specific Antigen (gag)
–Envelope (env) – gp41, gp120
–Polymerase (pol) – p31, p51, p66
• Nonstructural and regulatory genes:
tat, nef, rev, vif, vpu/vpx, vpr and LTR
p18 - shell
p24, p15 - core

7. RESERVOIR OF INFECTION
• Cases
• Carriers of HIV infection
Since HIV infection can take years to manifest
itself, the symptomless carrier can infect other
people for years

8. SOURCE OF INFECTION:
Greatest concentrations
• Blood,
• semen and
• CSF.
Lower concentrations
• Tears,
• Saliva,
• Breast milk,
• Urine,
• Cervical and Vaginal
secretions

9. Host Factors
Age:
• occurs in any age and seen mostly among 20-
49 years.
Sex:
• The sex ratio is equal.

10. HIGH-RISK GROUPS
• Male homosexuals
• Bisexuals
• Heterosexual partners (including female
sex workers)
• Intravenous drug abusers.
• Transfusion recipients of blood and blood
products
• Clients of STD
• Health Care Workers

11. Modes of transmission
Sexual Transmission
Blood transfusion
The use of HIV-contaminated needles and
syringes, including sharing by intravenous
drug users; transfusion of infected blood or
its components
Transplantation of HIV-infected tissues or
organs.

13. • HIV can be transmitted from Parent to child
(PTCT or vertical transmission).
– 15% to 35% through placental processes at birth.
– Breastfeeding and this can account for up to half
of mother-to-child HIV transmission.

14. Risk of transmission of HIV

15. Life cycle
Steps
1.Binding
2.Fusion
3.Uncoating
4.Reverse Transcription
5.Genome Integration
6.Genome Replication
7.Protein Synthesis
8.Protein Cleavage
9.Virus assembly and Spread

17. Incubation period
• Variable.
• Although the time from infection to the
development of detectable antibodies is
generally 1–3 months, the time from HIV
infection to diagnosis of AIDS has an observed
range of less than 1 year to 15 years or longer.
• The median incubation period in infected infants
is shorter than in infected adults.

18. Summary
Agent factor - HIV belong to ssRNA virus
Reservoir Infection – cases, carriers
Source of infection -
Host factors – sex, age, high risk group
Modes of transmission –
Life cycle – 9 steps
Incubation period – variable

19. We can’t make a cold blood murder
without knowing about the person
In the same way
We can’t identify or control the virus
without knowing about structure
and modes of transmission