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Viral Hemorrhagic fever: . The viral hemorrhagic fevers ( VHFs ) are a diverse group of animal and human illnesses that are caused by four different families of RNA viruses: 1- Arenaviridae . 2- Filoviridae . 3- Bunyaviridae . 4- Flaviviridae .

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Viral hemorrhagic fever

Viral Hemorrhagic fever:

The viral hemorrhagicfevers (VHFs) are a diverse group of animal and human illnesses that are caused by four different families of RNA viruses:

1- Arenaviridae.

2- Filoviridae.

3- Bunyaviridae.

4- Flaviviridae.

All types of VHF are characterized by fever and bleeding disorders and all can progress to high fever, shock and death in many cases.



Lassavirus, Juninvirus, and Machupo virus (MACV) are associated with hemorrhagic fever.


Lassa virus: West Africa.

Junin virus: Argentina.

Machupo virus: Bolivia.


-These are round, pleomorphic, and enveloped with a diameter of

120 nm.

- Nucleocapsid with two single-stranded RNA circular segments.


Viral reservoir:

Some Arenavirusesare zoonotic pathogens and are generally associated with rodentstransmitted disease.


Humans could be infected through mucosal exposure to aerosols, or by direct contact of broken skin with the infectious material, derived from infected rodents.

Ingestion of contaminated food, person-to-person contact is incriminated with transmission of the virus in some cases.


Pathogenesis and clinical picture:

Incubation period: 10-14 days.

The viruses infect macrophages, carried to bloodvessels ; endothelialcells infection, T-cell mediated response,

vascular damage.

Visceral hemorrhage.

Liver and spleen necrosis.

hemorrhage shock and cardiac damage.

Deathin 50% of cases.



Marburg virus and Ebola virus :

Epidemiology : Endemic in Africa.

1-Marburgvirus (Zimbabwe and Kenya).

2-Ebolavirus (Sudan and Zaire).


African green Monkeysand Wild Monkeys.


Monkeys-Human contact, human-human contact, and unknown

routes of transmission.

-The first infection was first detected among Laboratory workersin

Marburg, who had been exposed to tissue culture of cell line

prepared from Monkeys.



Filoviruses have a Single stranded RNA, which encodes

seven proteins

Envelopedfilamentous virus with Helicalnucleocapsid

measuring 800 to as long as 14000nm.

Pathogenesis and clinical picture

Pathogenesis and clinical picture:

-Eosinophiliccytoplasmicinclusions are seen in cells

infected with the virus.

-These virus infection disseminated with blood stream to

parenchymalcells of liver, spleen, lymphnodes, and lung.

-Widespread hemorrhage causes edema and hypovolemic



SGPT, and alkaline phosphatase elevated.

- Spleen destruction and lymph node enlargements.



-Super-group of at least 200 different viruses.

-Most are Arboviruses.


Enveloped, spherical virion with a diameter of 90-100 nm.

Single-stranded RNA nucleocapsids virus.


Transmission: Vector-born infection

1-Phlebovirus: Sandfly, genus : Phlebotomus.

2-Nairovirus: Ticks.

3-Bunyavirus: Mosquito.

Vertebrate host:

1-Phlebovirus: Sheep, cattle, others

2-Nairovirus: cattle, goats

3-Bunyavirus: Rodents, small mammals, and birds.


1-Rift Valley fever ; hemorrhagic fever, encephalitis.

2-Crimean-Congo -Hemorrhagic fever.

3-California encephalitis.

Pathogenesis and clinical picture1

Pathogenesis and clinical picture:

-Primaryviremia; flu-like symptoms, infection of vascular

endotheliumand Macrophageof Reticuloendothelial

system ; secondary viremia.

1-Vascular endothelial damage; leakage of plasma and

erythrocytes, hemorrhagic fever.

2- Cerebral edema and encephalitis.

3- Kidney hemorrhagic necrosis.

Crimean congo hemorrhagic fever caused by nairovirus

Crimean-Congo -Hemorrhagic fever caused by Nairovirus:




Flavivirusesare Arboviruses transmitted to man by vector (flavus (Latin term)means yellow).

Two types of Flaviviridaecause Hemorrhagicfever (H.F), and Yellowfever:

1-Dengue virus: DHF: dengue H.F, and DSS: dengue shock syndrome.

2-Yellow fever virus: Yellow fever and Hepatitis.


Mosquito of the genus Aedes.

Host: Human and Monkeys.(Zoonosis).


Dengue fever: Worldwide, especially tropics.

Yellow fever: Africa, and South America.



- Positive Single-strandedRNA viruses.

- Enveloped, Icosahedralnucleocapsid.

- Size: 40-65 nm.

Glycoprotein spikes (adhesion of virus to tissue).

-All Flavivirusesare

serologically related:

SoAnti-Virus serotype

antibodies could be

used as prophylactic

vaccine for others.

Pathogenesis and clinical picture2

Pathogenesis and clinical picture:

- Biting of the host skin by vector ( FemaleMosquito).

, inoculation of smallcapillariesbloodstream by virus in


-The virus will be carried by dendriticcells throughout small

capillaries to the targettissue.

-Target tissue:

1-The endothelial cells of Capillaries.

2-The blood Macrophage and monocytes.

-Blood phagocytes will transfer the microbe to the



This will initiate Primary Viremia (fever, chill, headaches, and flu-like symptoms within 3-7 days).

Secondary Viremia is associated with efficient replication of

virus in RES.

-This viremia can produce sufficient virus to infect:

1-Liver: Hepatitis, and Jaundice; yellow fever.

2-Brain: Encephalitis.

3-Vasculature and skin: Hemorrhage and shock.