Infectious diseases

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  1. 1. INFECTIOUS DISEASES Prepared by Khalid Al-Qaisi 1
  2. 2. Contents Definition of Infectious Diseases. Factors Influencing Disease Transmission Hepatitis A. Hepatitis B. Hepatitis C. Hepatitis D. Hepatitis E. HIV/AIDS. 2
  3. 3. 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. 3
  4. 4. 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 Transmission 4
  5. 5. 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 5
  6. 6. 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 6
  7. 7. 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 1550 days and mortality is less than 0.5%. Group:Group IV ((+)ssRNA) Order:Picornavirales Family:Picornaviridae Genus:Hepatovirus Species:Hepatitis A virus 7
  8. 8. Hepatitis A / Diagnosis specific diagnosis is made by the detection of HAV-specific IgM antibodies in the blood. It is detectable from one to two weeks after the initial infection and persists for up to 14 weeks. During the acute stage of the infection, the liver enzyme alanine transferase (ALT) is present in the blood at levels much higher than is normal. Hepatitis A virus is present in the blood (viremia) and feces of infected people up to two weeks before clinical illness develops.[ 8
  9. 9. 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 9
  10. 10. Hepatitis B / Definition Hepatitis B is an infectious illness of the liver caused by the hepatitis B virus (HBV) that affects hominoidea, including humans. Originally known as "serum hepatitis The virus is transmitted by exposure to infectious blood or body fluids such as semen and vaginal fluids, while viral DNA has been detected in the saliva, tears, and urine of chronic carriers. Perinatal infection is a major route of infection in endemic (mainly developing) countries. Other risk factors for developing HBV infection include working in a healthcare setting, transfusions, dialysis, acupuncture, tattooing, sharing razors or toothbrushes with an infected person, travel in countries where it is endemic, and residence in an institution. 10
  11. 11. Hepatitis B / Symptoms general ill-health loss of appetite Nausea Vomiting body aches mild fever dark urine Jaundice 11
  12. 12. Hepatitis B / Virology Hepatitis B virus (HBV) is a member of the hepadnavirus family. The virus particle (virion) consists of an outer lipid envelope and an icosahedral nucleocapsid core composed of protein The genome of HBV is made of circular DNA, but it is unusual because the DNA is not fully double-stranded. The incubation period is 45 160 days 12
  13. 13. Hepatitis B / Diagnosis The tests, called assays, for detection of hepatitis B virus infection involve serum or blood tests that detect either viral antigens (HBsAg and HBcAg) or antibodies produced by the host (anti-HBc IgM). Interpretation of these assays is complex. The hepatitis B surface antigen (HBsAg) is most frequently used to screen for the presence of this infection. Most hepatitis B diagnostic panels contain HBsAg and total anti-HBc (both IgM and IgG). 13
  14. 14. Hepatitis B / Prevention & Treatment Vaccines for the prevention of hepatitis B have been routinely recommended for infants since 1991 in the United States. Most vaccines are given in three doses over a course of months. The hepatitis B infection does not usually require treatment because most adults clear the infection spontaneously. None of the available drugs can clear the infection, they can stop the virus from replicating, These include antiviral drugs lamivudine (Epivir), adefovir (Hepsera), tenofovir (Viread), telbivudine (Tyzeka) and entecavir (Baraclude), and the two immune system modulators interferon alpha-2a and PEGylated interferon alpha-2a (Pegasys). 14
  15. 15. Hepatitis C / Definition Hepatitis C is an infectious disease affecting primarily the liver, caused by the hepatitis C virus (HCV). The infection is often asymptomatic, but chronic infection can lead to scarring of the liver and ultimately to cirrhosis, which is generally apparent after many years. In some cases, those with cirrhosis will go on to develop liver failure, liver cancer or life-threatening esophageal and gastric varices. The primary route of transmission in the developed world is intravenous drug use (IDU), while in the developing world the main methods are blood transfusions and unsafe medical procedures. Blood transfusion, transfusion of blood products, or organ transplants without HCV screening carry significant risks of infection. Vertical transmission of hepatitis C from an infected mother to her child occurs in less than 10% of pregnancies. 15
  16. 16. Hepatitis C / Symptoms Acute infection: Hepatitis C infection causes acute symptoms in 15% of cases. Symptoms are generally mild and vague, including a decreased appetite, fatigue, nausea, muscle or joint pains, and weight loss and rarely does acute liver failure result Chronic infection: This is defined as the presence of detectable viral replication for at least six months. Chronic hepatitis C can be associated with fatigue and mild cognitive problems and after several years may cause cirrhosis or liver cancer. 16
  17. 17. 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 15150 days 17
  18. 18. 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. 18
  19. 19. 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. 19
  20. 20. Hepatitis D / Definition Hepatitis D is an infectious disease affecting primarily the liver, Hepatitis D, also referred to as hepatitis D virus (HDV) and classified as Hepatitis delta virus, is a disease caused by a small circular enveloped RNA virus. HDV is considered to be a subviral satellite because it can propagate only in the presence of the hepatitis B virus (HBV). The routes of transmission of hepatitis D are similar to those for hepatitis B. Infection is largely restricted to persons at high risk of hepatitis B infection, particularly injecting drug users and persons receiving clotting factor concentrates. 20
  21. 21. 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%. 21
  22. 22. 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) F