1 Pathogenic Viruses Name of virus what family it belongs to what disease it causes, organ system affected DNA or RNA? Route of transmission; reservoirs, vectors Viral virulence factors (selected viruses) Immunizations

Herpes virus family Herpes family of DNA viruses –As a family, infects epithelial cells, lymph cells, and/or nerve cells. –Associated with latent infections and cancer –Spread by direct contact, fluid exchange –Herpes simplex 1 (cold sores) and 2 (STD) Drug treatment: acyclovir and related drugs Cannot be cured 2

Herpes continued –Varicella zoster: chickenpox; reactivation of latent state: shingles Varivax vaccine protects Drugs limit severity, duration of shingles –Epstein Bar virus: mononucleosis Infection of B cells and salivary glands Sore throat, fatigue, brittle spleen –Cytomegalovirus: CMV Common, subclinical infection Severe problem with AIDS, transplants, and cause of birth defects 3

Common cold viruses 1.Rhinovirus (picornavirus, small RNA virus) 1.Most common 2.Coronavirus (RNA virus) 1.Related to virus that causes SARS 1.Sudden acute respiratory distress syndrome 3.Adenovirus (DNA virus) 1.Some strains cause GI distress instead 4.Parainfluenza virus (RNA) 1.Related to flu and measles Spread by various forms of contact. 4

Parainfluenza family (RNA) Rubeola (measles) –Highly contagious, possible serious complications –Systemic infection, red rash –US: immunized with MMR vaccine; under control Mumps virus –Infects parotid glands, many other glands –Deafness most serious complication –US: immunized with MMR vaccine; under control Parainfluenza virus –Mild respiratory infection, cold symptoms 5

Parainfluenza family continued Respiratory syncytial virus (RSV) –Host: young children, can be fatal in infants –Cold symptoms in older individuals –Virus spreads in host by forming syncytia NOT a parainfluenza virus but similar spread and symptoms: German Measles (Rubeola) –Due to birth defects, women of child-bearing age should have immunity. –US: immunized with MMR vaccine; under control 6

Viruses of the GI tract All RNA viruses (either ss or ds) Enterovirus –Picornavirus family, includes polio, Hepatitis A Norovirus Rotavirus Spread by fecal-oral route of transmission; cause of outbreaks in daycares, restaurants, cruise ships, etc. vomiting and diarrhea. 7

Animal associated viruses Rhabdovirus: cause of rabies –Infects brain and salivary glands –Animals spread virus in saliva by biting –Slow acting, can be immunized against after –Nearly always fatal unless treated. Arboviruses –Unrelated viruses spread primarily by mosquitoes –Affect other creatures (horses, birds) as well as humans –Locally important ones cause encephalitis 8

continued St. Louis encephalitis Eastern Equine encephalitis –Kills people and horses West Nile virus –Generally mild in people, but kills certain birds Other arboviruses (e.g. Dengue fever) more of a tropical problem, but if global warming continues, becomes OUR problem. Endemic in Mexico. 9

10 Fungi Systemic infections –Generally acquired by inhalation of spores –Lung infections, may spread beyond into other tissues Histoplasma (histoplasmosis) –Most common in this area (Ohio and Miss. River valleys) –Soil contaminated with bird or bat droppings –Many people exposed with asymptomatic cases

11 Opportunists Aspergillus (aspergillosis) –Variety of species, very common in soil, plant materials –Serious infections in immunocompromised –Poisoning from aflatoxin from A. flavus Cryptococcus neoformans –Inhalation of spores, has predilection for CNS –Particularly serious in AIDS Pneumocystis carinii –Very protozoan like, but is a fungus –Most cases associated with AIDS –Serious lung infections: PCP (P. carinii pneumonia)

12 Protozoans Eukaryotic single-celled organisms –Eukaryotic means harder to treat infections Group responsible for human diseases are the animal-like protozoa. –Protozoa are widespread in nature, most not pathogenic Protozoa typically have life cycles –Simple, like vegetative cell and cyst (spore-like): Amoebas –Complex, like sporozoans have

Protozoal diarrheas Cryptosporidium –Primarily livestock and poultry, acquired fecal-oral through food or contaminated water. –Diarrhea, but systemic spread as well, highly dangerous to AIDS patients. Giardia lamblia: –Hiker’s diarrhea, from many water sources –Common cause of diarrhea; 1-4 weeks. 13

Other problem protozoal diseases Trypanosoma: various species, geographic locations –Cause of African sleeping sickness, spread by bite of tsetse fly: Infection of CNS, causes coma –Cause of Chagas disease, spread by bite of reduviid bug: eventually damages heart tissue. Leishmania: –Causes leishmaniasis, spread by sandfly (see “Gulf war”) –Various levels of severity of systemic disease Toxoplasma: toxoplasmosis –kills fetus; many organs in immune compromised. Part of life cycle involves cats, so pregnant women must stay away from litter box. 14