INFECTIOUS DISEASES

Prepared by Khalid Al-Qaisi

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Contents

Definition of Infectious Diseases.

Factors Influencing Disease Transmission

Hepatitis A.

Hepatitis B.

Hepatitis C.

Hepatitis D.

Hepatitis E.

HIV/AIDS.

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Infectious Diseases/ Definition

Infectious diseases are disorders caused by organisms

such as bacteria, viruses, fungi or parasites. Many

organisms live in and on our bodies. They're normally

harmless or even helpful, but some organisms under

certain conditions may cause disease.

Some infectious diseases can be passed from person to

person. Some, however, are transmitted via bites from

insects or animals. Others are acquired by ingesting

contaminated food or water or other exposures in the

environment.

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Agent

Host

Environment

• Age

• Sex

• Genetics

• Behaviour

• Nutritional status

• Health status

• Infectivity

• Pathogenicity

• Virulence

• Antigenic stability

• Survival

• Weather

• Housing

• Geography

• Occupational setting

• Air quality

• Food

Factors Influencing Disease

Transmission4

Hepatitis A / Definition

Hepatitis A (formerly known as infectious hepatitis)

is an acute infectious disease of the liver caused by

the hepatitis A virus (HAV).

It is usually spread by eating or drinking food or

water contaminated with infected feces. Shellfish

which have not been sufficiently cooked is a

relatively common source. It may also be spread

through close contact with an infectious person

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Hepatitis A / Symptoms

Fatigue

Fever

Nausea

Appetite loss

Jaundice, a yellowing of the skin or whites of the eyes due to hyperbilirubinemia

Bile is removed from blood stream and excreted in urine, giving it a dark amber colour

Diarrhea

Clay-coloured feces

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Hepatitis A / Virology

HAV enters the bloodstream through the epithelium of the oropharynx or intestine.

The hepatitis A virus is a picornavirus; it is non-enveloped and contains a single-stranded RNA packaged in a protein shell.

The incubation period is 15–50 days and mortality is less than 0.5%.

Group:Group IV ((+)ssRNA)

Order:Picornavirales

Family:Picornaviridae

Genus:Hepatovirus

Species:Hepatitis A virus

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Hepatitis A / Diagnosis

specific diagnosis is made by thedetection of HAV-specific IgMantibodies in the blood.

It is detectable from one to twoweeks after the initial infectionand persists for up to 14 weeks.

During the acute stage of theinfection, the liver enzymealanine transferase (ALT) ispresent in the blood at levelsmuch higher than is normal.

Hepatitis A virus is present in theblood (viremia) and feces ofinfected people up to two weeksbefore clinical illness develops.[

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Hepatitis A / Prevention & Treatment

Hepatitis A can be prevented by vaccination, good

hygiene and sanitation.

There are two types of vaccines: one containing

inactivated hepatitis A virus, and another containing

a live but attenuated virus.

There is no specific treatment for hepatitis A.

Sufferers are advised to rest, avoid fatty foods and

alcohol, eat a well-balanced diet, and stay

hydrated

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Hepatitis B / Definition

Hepatitis B is an infectious illness of the liver caused by thehepatitis B virus (HBV) that affects hominoidea, includinghumans. Originally known as "serum hepatitis“

The virus is transmitted by exposure to infectious blood orbody fluids such as semen and vaginal fluids, while viralDNA has been detected in the saliva, tears, and urine ofchronic carriers. Perinatal infection is a major route ofinfection in endemic (mainly developing) countries. Other riskfactors for developing HBV infection include working in ahealthcare setting, transfusions, dialysis, acupuncture,tattooing, sharing razors or toothbrushes with an infectedperson, travel in countries where it is endemic, and residencein an institution.

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Hepatitis B / Symptoms

general ill-health

loss of appetite

Nausea

Vomiting

body aches

mild fever

dark urine

Jaundice

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Hepatitis B / Virology

Hepatitis B virus (HBV) is amember of the hepadnavirusfamily.

The virus particle (virion)consists of an outer lipidenvelope and an icosahedralnucleocapsid core composed ofprotein

The genome of HBV is made ofcircular DNA, but it is unusualbecause the DNA is not fullydouble-stranded.

The incubation period is 45–160 days

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Hepatitis B / Diagnosis

The tests, called assays, fordetection of hepatitis B virusinfection involve serum or bloodtests that detect either viralantigens (HBsAg and HBcAg) orantibodies produced by the host(anti-HBc IgM). Interpretation ofthese assays is complex.

The hepatitis B surface antigen(HBsAg) is most frequently used toscreen for the presence of thisinfection.

Most hepatitis B diagnostic panelscontain HBsAg and total anti-HBc(both IgM and IgG).

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Hepatitis B / Prevention & Treatment

Vaccines for the prevention of hepatitis B have beenroutinely recommended for infants since 1991 in the UnitedStates. Most vaccines are given in three doses over a courseof months.

The hepatitis B infection does not usually require treatmentbecause most adults clear the infection spontaneously.

None of the available drugs can clear the infection, they canstop the virus from replicating, These include antiviral drugslamivudine (Epivir), adefovir (Hepsera), tenofovir (Viread),telbivudine (Tyzeka) and entecavir (Baraclude), and the twoimmune system modulators interferon alpha-2a andPEGylated interferon alpha-2a (Pegasys).

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Hepatitis C / Definition

Hepatitis C is an infectious disease affecting primarily the liver,caused by the hepatitis C virus (HCV). The infection is oftenasymptomatic, but chronic infection can lead to scarring of the liverand ultimately to cirrhosis, which is generally apparent after manyyears. In some cases, those with cirrhosis will go on to develop liverfailure, liver cancer or life-threatening esophageal and gastricvarices.

The primary route of transmission in the developed world isintravenous drug use (IDU), while in the developing world the mainmethods are blood transfusions and unsafe medical procedures.Blood transfusion, transfusion of blood products, or organ transplantswithout HCV screening carry significant risks of infection. Verticaltransmission of hepatitis C from an infected mother to her childoccurs in less than 10% of pregnancies.

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Hepatitis C / Symptoms

Acute infection:

Hepatitis C infection causes acute symptoms in 15% ofcases. Symptoms are generally mild and vague,including a decreased appetite, fatigue, nausea, muscleor joint pains, and weight loss and rarely does acuteliver failure result

Chronic infection:

This is defined as the presence of detectable viralreplication for at least six months. Chronic hepatitis Ccan be associated with fatigue and mild cognitiveproblems and after several years may cause cirrhosis orliver cancer.

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Hepatitis C / Virology

The hepatitis C virus (HCV) is a small, enveloped, single-stranded, positive-sense RNA virus.

Group: Group IV ((+)ssRNA)

Family: Flaviviridae

Genus: Hepacivirus

The incubation period is 15–150 days

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Hepatitis C / Diagnosis

Diagnostic tests for hepatitis C can be

divided into the following two general

categories: 1) serological assays that

detect antibody to hepatitis C virus (anti-

HCV); and 2) molecular assays that

detect, quantify, and/or characterize

HCV RNA genomes within an infected

patient.

Serological assays have been subdivided

into screening tests for anti-HCV, such as

the enzyme immunoassay (EIA), and

supplemental tests such as the

recombinant immunoblot assay (RIBA).

Detection of HCV RNA in patient

specimens by polymerase chain reaction

(PCR) provides evidence of active HCV

infection and is potentially useful for

confirming the diagnosis and monitoring

the antiviral response to therapy.

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Hepatitis C / Prevention & Treatment

There is no vaccine for hepatitis C. The risk of infection can be reduced by avoiding:

unnecessary and unsafe injections.

unsafe blood products.

unsafe sharps waste collection and disposal.

use of illicit drugs and sharing of injection equipment.

unprotected sex with hepatitis C-infected people.

sharing of sharp personal items that may be contaminated with infected blood.

tattoos, piercings and acupuncture performed with contaminated equipment.

Combination antiviral therapy with interferon and ribavirin has been the mainstay of hepatitis C treatment.

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Hepatitis D / Definition

Hepatitis D is an infectious disease affecting primarilythe liver, Hepatitis D, also referred to as hepatitis Dvirus (HDV) and classified as Hepatitis delta virus, is adisease caused by a small circular enveloped RNA virus.HDV is considered to be a subviral satellite because itcan propagate only in the presence of the hepatitis Bvirus (HBV).

The routes of transmission of hepatitis D are similar tothose for hepatitis B. Infection is largely restricted topersons at high risk of hepatitis B infection, particularlyinjecting drug users and persons receiving clottingfactor concentrates.

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Hepatitis D / Symptoms

Both superinfection and coinfection with HDV results in

more severe complications compared to infection

with HBV alone. These complications include a

greater likelihood of experiencing liver failure in

acute infections and a rapid progression to liver

cirrhosis, with an increased chance of developing

liver cancer in chronic infections. In combination with

hepatitis B virus, hepatitis D has the highest

mortality rate of all the hepatitis infections, at 20%.

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Hepatitis D / Virology

The HDV is a small, spherical virus with a 36 nm diameter. It has an outer coat containing three HBV envelope proteins.

Group: Group V ((-)ssRNA)

Family: Unassigned

Genus: Deltavirus

Species: Hepatitis delta virus

The incubation period is 30–60 days

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Hepatitis D / Diagnosis

The first step in the diagnosis ofhepatitis delta virus (HDV)infection is testing HBsAg-positiveindividuals for the antibody to theHD antigen (anti-HD).

Detection of serum HDV RNA —HDV RNA can be detected in

serum by either molecularhybridization or reversetranscriptase-polymerase chainreaction (RT-PCR) based assays

Detection of anti-HDVantibody — Total (IgM and IgG)anti-HDV antibodies can bedetected by EIAs or RIAs

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Hepatitis D / Prevention & Treatment

The vaccine for hepatitis B protects against hepatitis D

virus because of the latter's dependence on the

presence of hepatitis B virus for it to replicate.

Low quality evidence suggests that interferon alpha

can be effective in reducing the severity of the

infection and the effect of the disease during the time

the drug is given, but the benefit generally stops

when the drug is discontinued, indicating that it does

not cure the disease.

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Hepatitis E / Definition

Hepatitis E is a viral hepatitis (liver inflammation)

caused by infection with a virus called hepatitis E

virus (HEV).

It is spread mainly by the fecal-oral route due to

fecal contamination of water supplies or food;

person-to-person transmission is uncommon.

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Hepatitis E / Symptoms

Acute infection:

They may include jaundice, fatigue and nausea. The

symptomatic phase coincides with elevated hepatic

aminotransferase levels.

Chronic infection

Occasionally this may cause liver fibrosis and cirrhosis.

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Hepatitis E / Virology

HEV is a positive-sense single-stranded RNA icosahedral virus with a 7.5 kilobase genome.

Group: Group IV ((+)ssRNA)

Family: Hepeviridae

Genus: Hepevirus

Species: Hepatitis E virus

Incubation period is 20-40 days.

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Hepatitis E / Diagnosis

HEV can be detected in stoolapproximately one weekbefore the onset of illness andpersists for as long as twoweeks thereafter

The commonly used tests forHEV infection include detectionof IgM and IgG anti-HEVantibodies assay anddetection of HEV RNA. IgManti-HEV antibodies can bedetected during the first fewmonths after HEV infection,whereas IgG anti-HEVantibodies represent eitherrecent or remote exposure.

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Hepatitis E / Prevention & Treatment

Improving sanitation is the most important measure inprevention of hepatitis E; this consists of proper treatmentand disposal of human waste, higher standards for publicwater supplies, improved personal hygiene procedures andsanitary food preparation.

The vaccine appeared to be effective and safe, butdevelopment stopped for economical reasons, since hepatitisE is rare in developed countries.

The use of low doses of ribavirin over a three-month periodhas been associated with viral clearance in about two-thirdsof chronic cases.

Other possible treatments include peginterferon or acombination of ribavirin and peginterferon.

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HIV/AIDS / Definition

Human immunodeficiency virus infection / acquiredimmunodeficiency syndrome (HIV/AIDS) is a disease of thehuman immune system caused by infection with humanimmunodeficiency virus (HIV). During the initial infection, aperson may experience a brief period of influenza-likeillness. As the illness progresses, it interferes more and morewith the immune system, making the person much more likelyto get infections, including opportunistic infections and tumorsthat do not usually affect people who have working immunesystems.

HIV is transmitted primarily via unprotected sexualintercourse, contaminated blood transfusions, hypodermicneedles, and from mother to child during pregnancy,delivery, or breastfeeding

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HIV/AIDS / Symptoms

fever

large tender lymph nodes

throat inflammation

Rash

Headache

sores of the mouth and genitals.

peripheral neuropathy

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HIV/AIDS / Virology

Lentiviruses are transmitted as single-stranded, positive-sense, enveloped RNA viruses. Upon entry into the target cell, the viral RNA genome is converted (reverse transcribed) into double-stranded DNA by a virally encoded reverse transcriptase

Two types of HIV have been characterized: HIV-1 and HIV-2.

Group: Group VI (ssRNA-RT) virus.

Family:Retroviridae

Genus:Lentivirus

Incubation period 20-70 days

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HIV/AIDS / Diagnosis

detection of HIVantibody by the ELISAscreening test andconfirmation by Westernblot analysis

detection of the viralp24 antigen in serum

PCR tests to detect pro-viral DNA sequences

HIV culture, although thisis only performed incertain special clinicalsituations.

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HIV/AIDS / Prevention & Treatment

Consistent condom use reduces the risk of HIVtransmission by approximately 80% over the long term.

As of 2012 there is no effective vaccine for HIV orAIDS.

Antiviral therapy, combinations (or "cocktails") consistingof at least three medications belonging to at least twotypes, or "classes," of antiretroviral agents. Initiallytreatment is typically a non-nucleoside reversetranscriptase inhibitor (NNRTI) plus two nucleosideanalogue reverse transcriptase inhibitors (NRTIs);zidovudine (AZT) or tenofovir (TDF) and lamivudine.

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