Viral Pathogens Final Viral Disease Characteristics Are nonliving organisms Viruses effect every type of living organism o bacteria protozoa fungi plants animals Range of Disease o Benign harmless extremely malignant very harmful o Also everything in between wide range Example of being benign warts on humans No definitive treatment for any viral disease o hard to find selectively toxic drug Prevention o Education knowing how certain diseases are transmitted o Quarantine to take people who are ill and separate them from the rest of the healthy population cutting down on direct transmission routes o Vaccination most effective way to control viral disease No more cases of polio due to huge vaccination program Viral Disease Control Viral Disease Currently Controlled through Vaccination and Prevention smallpox eradicated world wide vaccination o U S childhood vaccination poliomyelitis mumps measles rubella o viral encephalitis U S vector control Viral Pathogens HIV Human Immunodeficiency virus Hepatitis viruses Influenza Influenza pathogen An acute respiratory disease of warm blooded vertebrates Reservoir primarily wild birds Often avirulent in reservoir Hosts o Domestic birds ducks chickens o Swine o Humans Influenza Virus Enveloped RNA virus sense o RNA in 8 segments codes for 11 proteins two important envelope proteins o neuraminidase helps virus penetrate mucus layer overlaying host cells o hemagglutinin used in adherence and penetration of host cell three major types A more variations B C o each major type has many variations o based on variations of different proteins molecules Neuraminidase Hemagglutinin What makes Influenza potentially dangerous o Can infect several species Virulence usually different among species o Virus can change readily genetic material How mutation antigenic drift recombination of RNA from other influenza strains antigenic shift Due to simultaneous infections of two different strains in same host Outcome Infect new species Become more virulent Influenza Historical Considerations o repeated epidemic one location and pandemics worldwide incidence of disease multiple countries continents throughout recorded history o One of the worst pandemics worldwide Spanish Flu of 1918 20 million deaths worldwide 500 000 Americans died within first 10 months o new types of the virus will certainly cause epidemics in the future Pandemics Influenza Disease o infection of the lower respiratory tract lungs o rapid onset o high fever o fatigue muscle aches o chest congestion coughing o may have cold like symptoms o moderate to severe symptoms lasting 1 3 weeks Influenza Complications serious ones from people who have lung problems o secondary bacterial pneumonia o often fatal in young elderly and immunocompromised transmission droplet or aerosol crowded conditions most cases seen winter and early spring Influenza Treatment o symptomatic antiviral prescription drug currently available Relenza Tamiflu limits symptoms and duration of disease Prevention o Vaccine available not always effective a cocktail mixed vaccine against several types each year a new vaccine must be produced Human Immunodeficiency Virus HIV pathogen Cause of Acquired Immunodeficiency Syndrome AIDS bacteria Human Immunodeficiency Virus Structure o Enveloped RNA virus Family Retroviridae o other retroviruses cause malignant disease and have been identified for many mammals and birds cancer immunodeficiency disease o reversetranscriptase converts viral RNA into DNA Two variation of the virus o HIV 1 and HIV 2 Origins of HIV o HIV 1 considered a new virus o evolved mutated from existing virus 1950s or earlier o disease unknown before 1980 o Early 1980 s first cases o evolved from the simian immunodeficiency virus o Earliest patients homosexual men IV drug users later persons receiving blood transfusions showing same disease The Epidemic morbidity o 35 million infected worldwide 2007 WHO CDC o 2 3 live in sub saharan Africa o 1 million persons in USA infected CDC o 5 million new cases year world wide Mortality o 20 000 deaths year in USA o 20 million deaths cumulative worldwide since 1981 UNAIDS Transmission o Virus found in body fluids o Transmissible levels in semen blood vaginal secretions o Modes of transmission sexual contact with infected person IV drug use with needle sharing passage from infected mother to infant receipt of blood transfusions blood product organs from an infected person o NOT modes of transmission casual contact mosquito Pathogenesis o virus infects lymphocytes macrophages dendritic cells others o main cell infected T helper lymphocyte o TH cell count in the blood used to monitor progression of the infection o normal count 800 1200 o 200 patients considered to have AIDS or will develop AIDS within 1 2 years HIV adsorption to TH CD4 Cells Figure 25 11 Transmission Pathogenesis o When too few TH cells exist patient unable to mount an adequate patient succumbs to opportunistic pathogens immune response o Stages of Infection Initial infection Latent Stage flu like symptoms antibodies develop against virus Asymptomatic no symptoms at all 1 8 years HIV Disease HIV related symptoms AIDS Course of Infection Figure 25 16 HIV Disease AIDS HIV Disease AIDS related Complex o weight loss o persistent swollen lymph nodes o recurring fever o blood abnormalities anemia leukopenia o some opportunistic infection recoverable o Kaposi s sarcoma possible AIDS o severe repeated opportunistic infections Death due to infection Opportunistic Infections of AIDS o Protozoa o Fungi o Bacteria o Viruses Cryptosporidium Toxoplasma Candida albicans Pneumocystis carinii Mycobacterium avium Mycobacterium tuberculosis Cytomegalovirus herpes simplex Prevention Treatment o Prevention Testing Both screening and definitive tests Education Vaccine under development o Treatment Treatment of opportunistic infections symptomatic passive immunization immunoglobulin Antiviral Drugs Combination Therapy Nitrogenous base analogs protease inhibitors Hepatitis Viruses pathogen General Characteristics o Many different types of viruses infect human liver cells o Three main types HBV Hepadnaviridae HAV Picornaviridae an enterovirus HCV Togaviridae o All cause inflammation of the liver hepatitis Hepatitis Viruses General Signs and symptoms of hepatitis o Jaundice yellow pigment o malaise fatigue o vomiting diarrhea o abdominal pain o fever o hepatomegaly liver problems Hepatitis B Virus HBV o Known as serum hepatitis o enveloped DNA