1. Bunyaviridae
Clayton M. Johnston

2. Bunyaviridae Largest family of mammal affecting viruses (250 viruses)
Arthropod- or rodent-borne vectors
Most are amplified in vertebrate hosts

3. Bunyaviridae Genus Disease(s) Bunyavirus LaCrosse encephalitis
Phlebovirus
Rift Valley Fever
Nairovirus
Crimean-Congo Hemorrhagic Fever
Tospovirus
Plant Virus
Hantavirus
Hemorrhagic Fever with Renal Syndrome
Hantavirus Pulmonary Syndrome

4. Structure
Virion Structure
Genomic Structure
Structural Proteins

5. Virion Structure Spherical 80-120 nm diameter Enveloped
Helical nucleocapsid
NO matrix protein

6. Genomic Structure (-) sense Linear ssRNA Three segments:
Large (L) codes for viral polymerase
Medium (M) codes for G1 and G2 glycoproteins
Small (S) codes for nucleocapsid

7. Structural Proteins Membrane Glycoproteins Nucleocapsid Protein
Viral Polymerase

8. Structural Proteins Membrane glycoproteins (G1 and G2) Polymerase (L)
Nucleocapsid proteins (N)

9. Membrane Glycoproteins
G1 and G2
Integral membrane proteins
Important in cell entry and pathogenesis

10. Nucleocapsid Protein
Complexes with genomic vRNA in virus, as well as with cRNA after infection, but not with mRNA
Necessary for virus replication and packaging

11. Viral Polymerase RNA-dependent RNA polymerase
Complexed with ribonucleocapsid in virion
Endonuclease activity to cleave host mRNA
Transcriptase activity for making cRNA and mRNA from vRNA
Helicase activity to unwind vRNA during transcription

12. Viral Replication Receptor mediated endocytosis Occurs in cytoplasm
Budding at Golgi apparatus or cell membrane

13. Hantavirus Replication Cycle
Attachment
Entry and Uncoating
Primary Transcription
Translation
Genome Replication
Secondary Transcription
Virion Assembly
Virion Release

14. Attachment
Viral G1 and G2 glycoproteins interact with cell surface receptors
Pathogenic hantavirus bind β3 integrins
Non-pathogenic hantaviruses bind β1 receptors

15. Entry and Uncoating
Virus particles bound to integrin receptors are taken in by receptor mediated endocytosis
Newly formed vesicles are acidified
Acidic environment changes confirmation of G1 and G2 glycoproteins
Viral and cell membranes fuse
Genomic material and polymerase are released into cytoplasm

16. Attachment and Entry

17. Primary Transcription
Transcription of negative sense vRNA to mRNA
Viral polymerase transcribes nucleoprotein-coated vRNA
Capped oligonucleotides from cell’s own mRNA are used to prime transcription (similar to Influenza virus)

18. Translation
L and S segments of mRNA are translated on free ribosomes in cytoplasm
M segment mRNA is translated on ER-bound ribosomes

19. Translation

20. Genome Replication
vRNA is used as a template by viral polymerase to make cRNA
cRNA is used as a template to make more negative sense strands of vRNA

21. Secondary Transcription
Extra vRNA synthesized during replication is used as template to make mRNA
Since more template is present after vRNA is replicated, more mRNA can be transcribed, and more viral proteins can be made
Persistent infection

22. Virion Assembly
Membrane-bound G1 and G2 peptides are transported to Golgi apparatus and carbohydrates are attached by N-linked glycosylation
vRNA complexes with N nucleocapsid protein, forms looped panhandle structure, and complexes with polymerase

23. Virion Assembly

24. Virion Release Two Mechanisms
Nucleocapsid complexes bud into the Golgi membrane with G1 and G2 embedded
Virion particle is formed inside Golgi apparatus
Virions are transported to cell membrane by vesicles and released by exocytosis
G1 and G2 embed into cell membrane through Golgi vesicles
Virions bud from cell membrane, not through Golgi apparatus

25. Attachment
Entry
Uncoating
Release
Transcription
Replication
Assembly
Translation

26. LaCrosse Encephalatis Bunyavirus
Mostly infects children younger than 16
Ades mosquitoes are the common vector
Squirrels and chipmunks are the amplifying host
Most common bunyavirus infection in the United States

27. LaCrosse Encephalatis Bunyavirus
Targets the brain
Symptoms may include:
Fever
Convulsions
Drowsiness
Focal neurological signs

29. Rift Valley Fever Phlebovirus
Most spread by sandfly or Ades species of mosquitoes
Causes abortion in livestock
Highly infectious by aerosolized blood
Distribution follows that of the host vectors
Immunization of livestock is the most effective way to control and prevent the disease

30. Rift Valley Fever Phlebovirus
Febrile disease in humans
Targets the liver
Symptoms often include:
Fever
Encephalitis
Retinal vasculitis (which may lead to blindness)
                   

32. Rift Valley Fever Distribution Map

33. Crimean-Congo Hemorrhagic Fever Nairovirus
Transmitted by ticks
Appears in the Middle East and Africa
Targets the liver and vascular endothelium
Symptoms include:
Headache
Pain in limbs
Often bleeding from many orifices

34. Crimean-Congo Hemorrhagic Fever Nairovirus

35. Hantavirus Enveloped ssRNA Virions 98 nm in diameter
Genome consists of three RNA segments

36. Transmission Vectors
Transmitted via aerosolized rodent urine, feces, and saliva
Deer mouse (Peromyscus maniculatus)
Cotton rat (Sigmodon hispidus)
White-footed mouse (Peromyscus leucopus)
Striped field mours (Apodemus agrarius)
Bank vole (Clethrionomys glareolus)
Rat (Rattus)

39. Hemorrhagic Fever with Renal Syndrome Hantavirus
Liver and vascular enothelium are targeted
Symptoms include:
Hemorrhage
Acute renal failure
Fever
Over 15% mortality rate

40. Hantavirus Pulmonary Syndrome Hantavirus
Lungs are targeted
Symptoms include
Fever
Acute respiratory distress
Over 50% mortality rate
Shock and cardiac complications often contribute to death

42. Prevention and Control
Vaccines
Hygiene
Vector Control

43. Vaccines E. coli expressed truncated nucleocapsid as an immunogen
Naked DNA
Recombinant non-pathogenic virus
Rodent brain-derived
Cell culture derived
Inactivated virus – being tried out in China

44. Hygiene Prevent aerosolization of virus from roden excrement
Dampen surfaces with bleach before cleaning
Control rodents and human contact with rodents

47. Host Defenses and Immune Response
Interferon is produced
Humor antibody has been shown to be related to the disappearance of virus from blood
Cytotoxic T-cells attack infected host cells
Inflammatory response

48. Treatment Early aggressive intensive care
Early use of inotropic agents (Dobutamine)
Early ventilation
Careful monitoring:
Oxygenation
Fluid balance
Blood pressure

49. Treatment General care, alleviation of symptoms
Ribavirin (Hemorrhagic Fever with Renal Syndrome)
ECMO (Hantavirus Pulmonary Syndrome)

50. Ribavirin Administered intravenously
Shown to be effective against Hemorrhagic Fever with Renal Syndrome
Not shown to be effective against Hantavirus Pulmonary Syndrome causing strains

51. Extra Corporeal Membrane Oxygenation (ECMO)
Removes blood from the body and artificially removes CO2 and adds O2
Costly
Difficult

52. ECMO

53. Laboratory Diagnosis Serology (ELISE for IgM) Immunohistochemistry
Reverse transcription and polymerase chain reaction (RT-PCR)
Virus isolation
Direct detection of antigen in blood and urine
Immunofluorescent test for antibodies

54. Problems Diagnosing Hantavirus
Symptoms often confused with influenza
Common signs of upper respiratory disease such as sore throat, sinusitis, and ear pain not usually present
Abdominal pain often misinterpreted as appendicitis
Many doctors outside endemic regions fail to recognize or have sufficient testing

55. Friday, March 26, 2004
PARKS AND PEOPLE
Glacier National Park
Death of Jerry O'Neal
The employees of Glacier National Park are deeply saddened to learn of the untimely passing of Deputy Superintendent Jerry O'Neal. O’Neal died early yesterday morning at a Kalispell, Mont., hospital following a brief illness.
O'Neal, 61, came down with an unknown illness last week and had undergone blood work and other diagnostic tests over the past few days. He was admitted to the Kalispell Regional Medical Center on Wednesday and died at 5:30 a.m. Thursday.

56. Friday, April 2, 2004 OPERATIONS NOTE Public Health Hantavirus Update
In view of the untimely death of Glacier National Park Deputy Superintendent Jerry O'Neal on March 25th from hantavirus pulmonary syndrome, we are issuing the following precautions and annual reminders.
Hantavirus pulmonary syndrome (HPS) is a viral disease transmitted to humans primarily through the inhalation of airborne dusts laden with the virus from infected rodent droppings (urine and saliva may also be sources of infection). Although hantaviruses have been a threat to human health worldwide for at least 50 years, HPS was first recognized in the United States in 1993 around the Four Corners area of the Southwest. Since then it has since been identified throughout the United States. Although rare, HPS is potentially deadly – mortality rates between 40 and 50% are common.