Pathogenic Viruses continued Herpes Virus family VZV, CMV, and EBV Hepatitis viruses Hep A, B, and C: all unrelated, and transmitted differently, but cause similar disease. Picornaviruses Mosquito-borne viruses of Arkansas Influenza HIV (guest speaker Debbie Biazo of NARAN)

Herpes virus family Human herpes viruses now numbered As a family: But common names easier to use. As a family: ability to become latent; predilection for either nervous tissue or lymphocytes; ability to cause cancer. Herpes roster: Herpes simplex, Varicella zoster, cytomegalovirus, Epstein Barr, roseola, Kaposi’s sarcoma virus.

Herpes Simplex viruses HHV1 (above the waist) Typically oral, cold sores; flu-like symptoms, etc. HHV2 (genital), STD and neonatal Painful, contagious sores on genitals, overlap w/ HHV1. Latency Viruses enter nearby nerve cells, remain until activated by stress of some sort, cause disease, then return. Spread and treatment: Person to person by direct contact; spread within host by forming syncytia, escape immune system. Acyclovir helps; no cure, lifetime infection.

Herpes family: Varicella Zoster Varicella: chicken pox; Zoster: shingles Chickenpox (not a pox virus), respiratory, disease becomes systemic with fever, malaise, skin lesions. Very contagious; usually mild, esp. in children Virus can become latent in nerves like Herpes simplex Recurrence: shingles; rash, pain, on one side Acyclovir can lessen symptoms Beware of salicylates + viruses: Reyes syndrome Vaccination: Varivax: attenuated vaccine

Herpes family: Cytomegalovirus CMV (HHV5): Infection results in enlarged cells Widespread asymptomatic infections, latency Virus shed in body fluids: sex, birth, transplants Problem for unborn, immunosuppressed, transplant patients; major cause of viral-induced birth defects. Epstein Bar Virus Cause of infectious mononucleosis Infects B lymphocytes and salivary glands With malaria, increased risk of cancer Burkitt’s Lymphoma

Hepatitis Hepatitis is inflammation of the liver Liver especially important in metabolism Breakdown of drugs, toxins, waste products Damage results in accumulation of bilirubin Bilirubin is stage in hemoglobin breakdown Results in yellow color: jaundice Hepatitis can be caused by several different viruses Hepatitis A, B, and C viruses all cause liver damage, but are unrelated viruses.

Hepatitis B A DNA virus: “Hepadnavirus” Hepatitis B released from live cells, so accumulates in high numbers in body fluids. Blood of infected person is rather infectious Cuts, piercing, sex, childbirth, etc. Large amounts of empty capsids ties up antibodies. After exposure, long incubation, long disease 10% have chronic infections The younger the host, the likelier chronic infection

Hep B continued Chronic infection correlated with liver destruction Liver tissue replaced by scar tissue; liver failure Long term exposure to virus increases risk of liver cancer Insertion of HBV DNA into chromosome may activate oncogenes Vaccination now recommended Because of bad result of early infection and great danger of liver damage, liver cancer. Recombinant vaccine.

Hepatitis A virus A small RNA virus, “Picornavirus” Transmitted by fecal-oral route Incubation for 1 month, followed by fever, nausea, anorexia, jaundice T cells attack infected liver cells No chronic infections, patients recover. Note comparisons to Hepatitis B: RNA vs DNA Shorter disease, few long term problems Mode of spread completely different

Hepatitis C Another RNA virus, different group: “Flavivirus” Causes chronic infections Can be mild, or destructive Long term infections increase risk of cancer. Transmission like Hep B: blood, sex, transplants New hepatitis viruses being regularly discovered

Picornaviruses Small RNA viruses Two kinds: enteric viruses, includes Hepatitis A and polio Rhinoviruses: major cause of common cold Rhinoviruses have many serotypes Variants, caused by easy mutation of RNA Immune system can’t recognize all differences, but enough similarities that colds become less severe, less frequent with age.

Arkansas Arboviruses Not an official taxonomic group, but short for “arthropod-borne” Includes Flaviviruses, Togaviruses, and others. Zoonotic, spread from animals to people by arthropod vectors, especially mosquitoes. Reservoirs may be birds, various mammals Result in two main types of illnesses Encephalitis, inflammation of the brain Hemorrhagic fever: high fever with bleeding

Arkansas Arboviruses Encephalitis: spread by skeeters In Arkansas: Eastern Equine; Togavirus; Also infects, kills horses. Most dangerous. St. Louis encephalitis, Flaviviral diseases; Human disease. Usually not serious. West Nile virus Flavivirus; imported to US, spread from NYC Disease mostly in young and elderly

Orthomyxovirus Influenza: a serious respiratory disease Virus has a segmented genome 8 different RNA molecules Spikes: Hemagglutinin (for infecting cells) and neuraminidase (for escaping them) Antigenic drift and shift Drift: small mutations, making host susceptible Shift: major mixing of RNAs, whole new virus. Attack on respiratory tract Kills ciliated epithelial cells, allows bacterial infections. Release of interferon causes symptoms.

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influenza Changes in H and N (antigenic shift) Mixing of viruses that infect birds, pigs, produce new strains able to jump to humans. New antigenic type leaves population unprotected Numerous epidemics throughout history Flu of 1918-1919 killed 20 million Asia watched very carefully Flu vaccines made from deactivated viruses Slow process, so every year correct strains are “guessed”.

HIV/AIDS Infection 4 main types of cells infected, esp. T helper cells Have CD4 glycoprotein on surface After RNA is copied into cDNA, cDNA inserts Infection is for life Chronic infection T cells continually made, continually destroyed Eventually, host loses AIDS diagnosis: CD4 count below 200/µl; opportunistic infections

Treatment and prevention Prevention is easy Practice monogamous sex, avoid shared needles HIV cannot be spread by casual contact, skeeters Fastest growing victim demographic is YOU. Not just a “gay disease” Treatment is expensive, but usually works Nuceloside analogs, protease inhibitors Processing viral proteins requires protease About $1500 a month for drugs