Infectious Diseases Basics
Eradication vs elimination:
● Eradication = total and permanent global reduction to zero new cases of a
contagious disease, through targeted action with no further need for the continued
epidemic control → has been achieved for smallpox
● Elimination = reduced incidence of an infectious disease to zero new cases in a
defined geographical area as a result of targeted efforts, but with the need for
continued monitoring to prevent new/increased transmission → e.g. measles and
polio
Serological shift:
● Serological/antigenic shift can results in novel and highly pathogenic strains of
human influenza
● The serological shift can lead to outbreaks in population where susceptibility has
increased due to reduced natural exposure, especially if vaccination coverage is
suboptimal
● Public health implications: a change in pattern of seroprevalence within population
reflecting the proportion of individuals who have antibodies to an infection/bacteria
due to past exposure or vaccination
Harm Reduction
Harm reduction = policies, programmes and practices that aim to minimise the negative
health/social/legal impacts associated with drug use, drug policies and drug laws
● HR is grounded in justice and human rights by focusing on positive change and on
working with people without judgement, coercion, discrimination or requiring that
people stop using drugs as a precondition of support
● NSP = needle syringe program → decreases hepatitis and HIV spread, and
increased QoL and mortality for these diseases
1
,Hepatitis
Functions of the liver:
● Filter toxins, drugs, bilirubin
● Factory of bile, proteins and lipids
● Storage of lipid metabolism, store and release glucose
Hepatitis = inflammation of the liver
● Various causes: drugs, toxins, alcohol, autoimmune, viruses
● Chronic inflammation → fibrosis → liver damages → liver cirrhosis
Acute hepatitis (shows physical symptoms):
● Pre-icteric phase
○ General malaise
○ Fatigue
○ Nausea, loss of appetite
○ Urticaria
○ Fever
○ Painful joints
○ Itching
○ Jaundice
● Chance of icteric phase with symptoms:
○ HAV = 75%
○ HBV = 50%
○ HCV = 15%
● Diagnosis
○ Physical examination
○ Blood tests (INR, bilirubin, AST, ALT, ALP, albumin, platelets, SR/IgG) ← test
liver function
○ Confirm diagnosis with virology labs (anti-HAV IgM, anti-HBc IgM, anti-HCV/
HCV-RNA, anti-HEV/HEV-RNA
■ DD: autoimmune, alcohol, toxic hepatitis
● Treatment:
○ No specific treatment for A, D and E
○ Suspend alcohol and drugs
○ Acute HBV: sometimes oral treatment with antivirals
○ Acute HCV: treat!!
○ Fulminant hepatitis: rare (1%) but serious → liver transplantation is
sometimes required
● Disease control of acute hepatitis:
○ Info to patient (advice on fecal-oral/parenteral transmission)
○ Contact tracing
○ Protection (PEP, vaccine, immunoglobulin for HAV/HBV)
○ Notification
○ Harm reduction measures (needle exchange, OAT, DCR (drug consumption
rooms))
2
,Natural history of hepatitis:
● Acute → spontaneous clearance (HBV in adults have a 95% chance of clearance)
● Otherwise: Chronic infection → cirrhosis → HCC → ESLD → death
● End stage liver disease (ESLD) = ascites, bleeding esophageal varices, hepatic
encephalopathy, spontaneous bacterial peritonitis, HCC, death
Hep A - E:
Hep A Hep B Hep C Hep D Hep E
Route of Fecal-oral Blood, sexual Blood, (sexual Blood Fecal-oral
transmission (mostly contact, vertical contact, vertical (mostly through
person-person) transmission transmission) water/food)
Risk groups Endemic areas, Endemic areas, PWID, blood Endemic areas, Endemic areas,
travellers, immigrants, transfusions, immigrants, travellers
(PWID) PWID immigrants PWID
Endemic Asia and SSA Asia and SSA Asia, Russia Mongolia, and East and South
regions and USA SSA Asia
Incubation 2-6 weeks 2-6 months 1-3 months 3-6 weeks 3-8 weeks
period
Chronic No Yes Yes Yes No
Vaccine Yes Yes No No (but Yes, but not
B-vaccine) widespread yet
Treatment No Yes (control) Yes (cure) Yes (control) No
Prevention Vaccine, Vaccine, safe Needle Vaccine (hep Sanitary
sanitary sex, needle exchange, B), safe sex standards,
standards exchange opiate vaccine
substitution
treatment
Hepatitis A:
● Extremely stable virus
● Spread mainly through eating food/drinking water that has been contaminated by
feces of an infected person
○ Also by eating raw shellfish from sewage-contaminated waters
● Outbreaks of HAV may occur among MSM, PWID and homeless people
● Incubation period = 2-6 weeks
● Virus present in blood and feces 10-12 days after infection
● Virus excretion may continue for up to 3 weeks after onset of symptoms
○ Adults usually have quite severe symptoms, while children often have no
symptoms
● HAV prevention:
○ Adequate supplies of safe drinking water
○ Proper disposal of sewage within communities
○ Personal hygiene practices
Hepatitis B:
● HbsAg positive > 6 months
● Transmission via blood, sex or vertical during childbirth
3
, ● 1.2 million new infections each year
● Infected early in life; mother-child or child-child
○ If infected as a newborn/child: 90% chance of chronic infection
○ If infected as an adult: 1% chance of chronic infection (99% of clearance)
● Incubation time = 2-6 months; this is the window to start PreP!!
● Highest prevalence in Asia and SSA
● 15-40% develop cirrhosis, liver failure of HCC (ESLD)
● Natural history of chronic HBV:
○ Immune tolerance “child phase” → high level of virus (and transmission risk)
○ Immune clearance “youth phase” → lower level of virus, higher level of
inflammation (usually quite short, otherwise risk of permanent liver damage)
○ Inactive-carrier phase/surveillance “adult phase” → low levels of virus and
`no signs of inflammation
○ Sometimes reactivation phase → increased level of virus in ups and downs
(and transmission risk, but not as high as risk was as a child), inflammation
goes up and down as well (increased risk of severe liver damage, HCC,
cirrhosis etc); treatment with antivirals is needed in this stage
No new infection is possible after clearance!
● Hepatitis B treatment:
○ Control (not cure)
○ Prevention of long-term negative clinical outcomes by durable suppression of
HBV DNA
○ Primary treatment endpoint → sustained decrease in serum HBV DNA levels
to low or undetectable
○ Secondary treatment endpoints → decrease or normalize serum ALT, improve
liver histology, induce HBsAg/HBeAg loss or seroconversion
● Prevention:
○ Vaccination (available since 1980s) → effectiveness of 96%
■ All babies should receive vaccine asap after birth (within 24 hours),
followed by 2-3 doses of vaccine at least 4 weeks apart
○ To reduce risk of spreading hep B:
■ Practice safe sex by using condoms
■ Avoid sharing needles or any equipment used for injecting drugs,
piercing or tattooing
Hepatitis C:
● Highest prevalence in China, Pakistan, India, Russia and USA
● Transmission routes: PWID!!, needle transmission, snorting cocaine
○ Low risk of sexual sexual transmission (1%), but a little bit higher in anal
intercourse (MSM); also low risk of vertical transmission (5%)
● Natural history of HCV:
○ Chronic HCV with duration of >6 months
4
Eradication vs elimination:
● Eradication = total and permanent global reduction to zero new cases of a
contagious disease, through targeted action with no further need for the continued
epidemic control → has been achieved for smallpox
● Elimination = reduced incidence of an infectious disease to zero new cases in a
defined geographical area as a result of targeted efforts, but with the need for
continued monitoring to prevent new/increased transmission → e.g. measles and
polio
Serological shift:
● Serological/antigenic shift can results in novel and highly pathogenic strains of
human influenza
● The serological shift can lead to outbreaks in population where susceptibility has
increased due to reduced natural exposure, especially if vaccination coverage is
suboptimal
● Public health implications: a change in pattern of seroprevalence within population
reflecting the proportion of individuals who have antibodies to an infection/bacteria
due to past exposure or vaccination
Harm Reduction
Harm reduction = policies, programmes and practices that aim to minimise the negative
health/social/legal impacts associated with drug use, drug policies and drug laws
● HR is grounded in justice and human rights by focusing on positive change and on
working with people without judgement, coercion, discrimination or requiring that
people stop using drugs as a precondition of support
● NSP = needle syringe program → decreases hepatitis and HIV spread, and
increased QoL and mortality for these diseases
1
,Hepatitis
Functions of the liver:
● Filter toxins, drugs, bilirubin
● Factory of bile, proteins and lipids
● Storage of lipid metabolism, store and release glucose
Hepatitis = inflammation of the liver
● Various causes: drugs, toxins, alcohol, autoimmune, viruses
● Chronic inflammation → fibrosis → liver damages → liver cirrhosis
Acute hepatitis (shows physical symptoms):
● Pre-icteric phase
○ General malaise
○ Fatigue
○ Nausea, loss of appetite
○ Urticaria
○ Fever
○ Painful joints
○ Itching
○ Jaundice
● Chance of icteric phase with symptoms:
○ HAV = 75%
○ HBV = 50%
○ HCV = 15%
● Diagnosis
○ Physical examination
○ Blood tests (INR, bilirubin, AST, ALT, ALP, albumin, platelets, SR/IgG) ← test
liver function
○ Confirm diagnosis with virology labs (anti-HAV IgM, anti-HBc IgM, anti-HCV/
HCV-RNA, anti-HEV/HEV-RNA
■ DD: autoimmune, alcohol, toxic hepatitis
● Treatment:
○ No specific treatment for A, D and E
○ Suspend alcohol and drugs
○ Acute HBV: sometimes oral treatment with antivirals
○ Acute HCV: treat!!
○ Fulminant hepatitis: rare (1%) but serious → liver transplantation is
sometimes required
● Disease control of acute hepatitis:
○ Info to patient (advice on fecal-oral/parenteral transmission)
○ Contact tracing
○ Protection (PEP, vaccine, immunoglobulin for HAV/HBV)
○ Notification
○ Harm reduction measures (needle exchange, OAT, DCR (drug consumption
rooms))
2
,Natural history of hepatitis:
● Acute → spontaneous clearance (HBV in adults have a 95% chance of clearance)
● Otherwise: Chronic infection → cirrhosis → HCC → ESLD → death
● End stage liver disease (ESLD) = ascites, bleeding esophageal varices, hepatic
encephalopathy, spontaneous bacterial peritonitis, HCC, death
Hep A - E:
Hep A Hep B Hep C Hep D Hep E
Route of Fecal-oral Blood, sexual Blood, (sexual Blood Fecal-oral
transmission (mostly contact, vertical contact, vertical (mostly through
person-person) transmission transmission) water/food)
Risk groups Endemic areas, Endemic areas, PWID, blood Endemic areas, Endemic areas,
travellers, immigrants, transfusions, immigrants, travellers
(PWID) PWID immigrants PWID
Endemic Asia and SSA Asia and SSA Asia, Russia Mongolia, and East and South
regions and USA SSA Asia
Incubation 2-6 weeks 2-6 months 1-3 months 3-6 weeks 3-8 weeks
period
Chronic No Yes Yes Yes No
Vaccine Yes Yes No No (but Yes, but not
B-vaccine) widespread yet
Treatment No Yes (control) Yes (cure) Yes (control) No
Prevention Vaccine, Vaccine, safe Needle Vaccine (hep Sanitary
sanitary sex, needle exchange, B), safe sex standards,
standards exchange opiate vaccine
substitution
treatment
Hepatitis A:
● Extremely stable virus
● Spread mainly through eating food/drinking water that has been contaminated by
feces of an infected person
○ Also by eating raw shellfish from sewage-contaminated waters
● Outbreaks of HAV may occur among MSM, PWID and homeless people
● Incubation period = 2-6 weeks
● Virus present in blood and feces 10-12 days after infection
● Virus excretion may continue for up to 3 weeks after onset of symptoms
○ Adults usually have quite severe symptoms, while children often have no
symptoms
● HAV prevention:
○ Adequate supplies of safe drinking water
○ Proper disposal of sewage within communities
○ Personal hygiene practices
Hepatitis B:
● HbsAg positive > 6 months
● Transmission via blood, sex or vertical during childbirth
3
, ● 1.2 million new infections each year
● Infected early in life; mother-child or child-child
○ If infected as a newborn/child: 90% chance of chronic infection
○ If infected as an adult: 1% chance of chronic infection (99% of clearance)
● Incubation time = 2-6 months; this is the window to start PreP!!
● Highest prevalence in Asia and SSA
● 15-40% develop cirrhosis, liver failure of HCC (ESLD)
● Natural history of chronic HBV:
○ Immune tolerance “child phase” → high level of virus (and transmission risk)
○ Immune clearance “youth phase” → lower level of virus, higher level of
inflammation (usually quite short, otherwise risk of permanent liver damage)
○ Inactive-carrier phase/surveillance “adult phase” → low levels of virus and
`no signs of inflammation
○ Sometimes reactivation phase → increased level of virus in ups and downs
(and transmission risk, but not as high as risk was as a child), inflammation
goes up and down as well (increased risk of severe liver damage, HCC,
cirrhosis etc); treatment with antivirals is needed in this stage
No new infection is possible after clearance!
● Hepatitis B treatment:
○ Control (not cure)
○ Prevention of long-term negative clinical outcomes by durable suppression of
HBV DNA
○ Primary treatment endpoint → sustained decrease in serum HBV DNA levels
to low or undetectable
○ Secondary treatment endpoints → decrease or normalize serum ALT, improve
liver histology, induce HBsAg/HBeAg loss or seroconversion
● Prevention:
○ Vaccination (available since 1980s) → effectiveness of 96%
■ All babies should receive vaccine asap after birth (within 24 hours),
followed by 2-3 doses of vaccine at least 4 weeks apart
○ To reduce risk of spreading hep B:
■ Practice safe sex by using condoms
■ Avoid sharing needles or any equipment used for injecting drugs,
piercing or tattooing
Hepatitis C:
● Highest prevalence in China, Pakistan, India, Russia and USA
● Transmission routes: PWID!!, needle transmission, snorting cocaine
○ Low risk of sexual sexual transmission (1%), but a little bit higher in anal
intercourse (MSM); also low risk of vertical transmission (5%)
● Natural history of HCV:
○ Chronic HCV with duration of >6 months
4
