Double-Stranded RNA Viruses Lange Chapter 40 for rotavirus, Chapter 42 for colorado tick fever SAMUEL AGUAZIM M.D

Family Reoviridae Non-Enveloped Both double-stranded (ds) RNA and double-shelled icosahedral capsids. Segments( 10-11) Virion contains an RNA-dependent RNA polymerase.

Three Viruses in Family Reoviridae Rotavirus Orbivirus Reovirus

Rotavirus Major cause of infantile diarrhea worldwide Fecal oral transmission ( common in preschools and day care centers) Vomiting and fever usually precede diarrhea In healthy infants, illness lasts 3-9 days The major serotype (A) causes diarrhea and dehydration in infants <2 years, mild diarrhea in older kids, and severe diarrhea , leading to death in malnourished individuals. This noninflammatory diarrhea is caused by protein nsP4, a viral enterotoxin.

Family Orbivirus: Colorado tick fever virus Transmitted by the tick Dermacentor andersoni One of the causes of viral encephalitis Camping and hiking in the Rocky Mountains

The incubation period of Colorado tick fever virus is usually 3-4 days after reported tick exposure, followed by a self-limiting illness that can present with Fever Chills Myalgias Prostration Rash

Family Reovirus Asymptomatic common May also cause a febrile disease

Chikungunya Chikungunya is most prevalent in West Africa and presents with:Fever Polyarthralgia Macular or maculopapular rash starting on the limbs and trunk

Astroviruses Astroviruses are nonenveloped RNA viruses similar in size to polioviruses. They have a characteristic five- or six-pointed morphology. These viruses cause watery diarrhea, especially in children. Most adults have antibodies against astroviruses, suggesting that infection occurs commonly. No antiviral drugs or preventive measures are available.

Japanese Encephalitis Virus Members of the flavivirus Causes outbreaks of encephalitis in asian countries. Transmitted to humans by mosquitoes from the reservior hosts, birds and pigs. No antiviral therapy An inactivated vaccine is available

HUMAN T-CELL LYMPHOTROPIC VIRUS Disease: adult t-cell leukemia/lymphoma and HTLV associated myelopathy a.k.a tropical spastic paraparesis or chronic progressive myelopathy. Characteristics- HTLV is a member of retrovirus family. Causes malignant transformation of CD4 positive T cells. Transmission: IVDU, sexually, blood and breast feeding.

Lab DX: detect anti-HTLV antibodies in the patients serum using ELISA. WESTERN BLOT PCR.

Cache Valley Virus This virus was first isolated in Utah in 1956 but is found throughout the western hemisphere. It is a bunyavirus transmitted by Aedes, Anopheles, or Culiseta mosquitoes from domestic livestock to people. It is a rare cause of encephalitis in humans. There is no treatment or vaccine for Cache Valley virus infections.

Hendra Virus This virus was first recognized as a human pathogen in 1994, when it caused severe respiratory disease in Hendra, Australia. It is a paramyxovirus resembling measles virus and was previously called equine morbillivirus. The human infections were acquired by contact with infected horses, but fruit bats appear to be the natural reservoir. There is no treatment or vaccine for Hendra virus infections.

Human Metapneumovirus This paramyxovirus was first reported in 2001 as a cause of severe bronchiolitis and pneumonia in young children in the Netherlands. It is similar to respiratory syncytial virus (also a paramyxovirus) in the range of respiratory tract disease it causes. Serologic studies showed that most children have been infected by 5 years of age and that this virus has been present in the human population for at least 50 years.

Nipah Virus Nipah virus is a paramyxovirus that caused encephalitis in Malaysia and Singapore in 1998 and 1999. People who had contact with pigs were particularly at risk for encephalitis caused by this previously unrecognized virus. There is no treatment or vaccine for Nipah virus infections.

Poxviruses of Animal Origin Four poxviruses cause disease in animals and also cause poxlike lesions in humans on rare occasions. They are transmitted by contact with the infected animals, usually in an occupational setting.

Cowpox virus causes vesicular lesions on the udders of cows and can cause similar lesions on the skin of persons who milk cows. Pseudocowpox virus causes a similar picture but is antigenically distinct. Orf virus is the cause of contagious pustular dermatitis in sheep and of vesicular lesions on the hands of sheepshearers.

Monkeypox virus is different from the other three; it causes a human disease that resembles smallpox. It occurs almost exclusively in Central Africa. Any new case of smallpox like disease must be precisely diagnosed to ensure that it is not due to smallpox virus. For these reasons, it is important to ensure that new cases of smallpox like disease are due to monkey pox virus

Spumaviruses Spumaviruses are a subfamily of retroviruses that cause a foamy appearance in cultured cells. They can present a problem in the production of viral vaccines if they contaminate the cell cultures used to make the vaccine. There are no known human pathogens.

Tacaribe Complex of Viruses The Tacaribe2 complex contains several human pathogens, all of which cause hemorrhagic fever. The best known are Sabia virus in Brazil, Junin virus in Argentina, and Machupo virus in Bolivia. Hemorrhagic fevers, as the name implies, are characterizedby fever and bleeding into the gastrointestinal tract, skin, and other organs. The bleeding is due to thrombocytopenia. Transmission: food and water contaminated with rodents excreta Treatment: ribavarin Prevention: no vaccine available

whitewater arroyo virus This virus is the cause of a hemorrhagic fever/acute respiratory distress syndrome in the western part of the United States. It is a member of the arenavirus family, as is Lassa fever virus, a cause of hemorrhagic fever in Africa. Wood rats are the reservoir of this virus, and it is transmitted by inhalation of dried rat excrement. This mode of transmission is the same as that of the hantavirus, Sin Nombre virus (see page There is no established antiviral therapy and there is no vaccine.

Ebola: Pathophysiology Ebola virus is a enveloped, nonsegmented, negative-sense, single-stranded RNA virus with a helical capsid. Along with Marburg virus, they make up the virus family Filoviridae, named for their thread-like filamentous structure.

Transmission of Ebola occurs mainly through person-to-person contact with an infected person’s bodily fluids such as blood, vomit, urine, feces, and even sweat.

Laboratory studies have shown initiation of infection can occur through ingestion, inhalation, or compromised areas of skin. Aerosolized forms have been shown to be highly infectious in the laboratory setting, and infection involving aerosols generated during medical procedures have been documented.

The natural reservoir for Ebola, along with the mode of transmission from reservoir to primates, remains a mystery. Bats have been suspected as being a non-primate reservoir because of their presence in areas during several outbreaks and isolation of Marburg virus from fruit bats in Uganda.

Incubation period is usually about five to seven days, but in some cases may exceed two weeks. Once Ebola enters the body, the virus infects and lyses endothelial cells, hepatocytes, macrophages, and dendritic cells (antigen-presenting cells), releasing more particles into the extracellular fluid. Viral particles spread to regional lymph nodes, resulting in further rounds of replication and dissemination to other lymphoid tissues.

Infection of macrophages and other cells causes release of proinflammatory mediators, cytokines, and chemokines, which causes a systemic inflammatory syndrome. Impaired dendritic function and lymphocyte apoptosis causes a decreased adaptive immunity.

Coagulation defects in Ebola virus infection occurs indirectly through the synthesis of tissue factor, which triggers the extrinsic coagulation pathway. In addition, the proinflammatory cytokines induce macrophage production of tissue factor.

Risk factors include recent travel to an African region where Ebola virus outbreaks have occurred, laboratory accident when working with Ebola, or illness in a healthcare worker during an epidemic in Africa.

Ebola: Clinical Manifestation Patients typically present with an  Other signs and symptom abrupt onset of fever greater than 38.6°C (101.5°F), chills, and general malaise.s can include weakness, headache, myalgia, nausea, vomiting, diarrhea, nonproductive cough, pharyngitis, and abdominal pain. Bradycardia can sometimes follow the high fever. 

Ebola: Clinical Manifestation Symptoms persist over a few days before causing signs of hypotension, stupor, and prostration. Coagulation defects usually present as conjunctival hemorrhages, easy bruising, and difficulty to clot after venipuncture - contrary to the accounts of “bleeding from all orifices.

Ebola: Clinical Manifestation Development of a non-pruritic maculopapular rash on the upper body during the first week of illness may be a sign of an Ebola virus infection.

Ebola: Clinical Manifestation Fatal outcomes associated with Ebola virus usually occur due to severe intravascular volume depletion, metabolic abnormalities, and impaired oxygen delivery.

BALANCE BETWEEN POWER AND CHARACTER DETERMINE THE LEVEL OF SUCCESS YOU ENJOY…. DRS