Epidemiology & Transmission of Arboviruses

arthropod-borne viruses (arboviruses)

represent ecologic groupings of viruses with complex transmission cycles involving arthropods

roboviruses

rodent borne viruses

fevers (benign), encephalitis, hemorrhagic fevers

Arbovirus diseases fall into three general categories:

major mosquito-borne diseases

yellow fever, dengue, chikungunya, Japanese B encephalitis, equine encephalitides, West Nile fever, and Zika

major rodent-borne viral diseases

hantavirus infections, Lassa fever,and South American hemorrhagic fevers

urban, sylvatic, arthropod sustained

cycles of arbovirus transmission:

urban transmission of arbovirus

Favored by the presence of relatively large numbers of humans living in close proximity to arthropod (usually mosquito) species capable of virus transmission

sylvatic transmission of arbovirus

single nonhuman vertebrate - humans are tangential hosts through accidental intrusion into a zoonotic transmission cycle

maintaining the infection cycle

sylvatic transmission is not important in:

jungle yellow fever

example of sylvatic transmission of arbovirus

dengue

example of urban transmission of arbovirus

multiple vertebrate reservoirs (sylvatic)

Western equine encephalitis, eastern equine encephalitis, and California viruses

arthropod sustained

Arthropods (especially ticks) sustain the reservoir by transovarial (via ovaries) transmission of virus to their progeny, with amplification of the cycle by spread to and from small mammals

western equine encephalitis

example of arthropod sustained transmission

Togaviridae family

Alpha viruses often establish persistent infections in mosquitoes and are transmitted between vertebrates by mosquitoes or other blood-feeding arthropods

rubella virus

Classified in a separate genus in the Togaviridae family- No arthropod vector and is not an arbovirus

Flaviviridae family

transmitted among vertebrates by mosquitoes and ticks, but others are transmitted among rodents or bats without any known insect vectors

hepatitis C virus

classified in a separate genus in the Flaviviridae family - no arthropod vector and is not an arbovirus

enveloped

general property of togaviridae and flaviviridae

encephalitis

what can togaviridae and flaviviridae typically cause

positive ss RNA

what is the genetic material for togaviridae and flaviviridae

myeloid and and lymphoid cells or in vascular endothelium

Primary viral multiplication of Togavirus and Flavivirus encephalitis occurs in either:

infect nerve cells

Multiplication in the central nervous system depends on the ability of the virus to pass the blood-brain barrier and to:

viremia

Arthropod vectors acquire the virus by sucking blood during this period—the first step in its dissemination to other hosts.

unknown

the mechanisms by which Togavirus and Flavivirus cross BBB:

arbovirus-induced encephalitis

Widespread neuronal degeneration occurs in all:

4 and 21 days

Incubation periods of the encephalitis are between ___________ for Togavirus and Flavivirus

flaviviridae

zika belongs to:

low transmissibility, vertical transmission (mother to baby)

transmission of zika?

mosquito

what is the vector for zika

humans

vertebrate host of zika?

sexually

Zika is an arbovirus but also transmitted _______

zika

Which arbovirus causes a benign disease with rash and fever unless it occurs in a pregnant patient, in whom it can infect the developing fetus and result in multiple congenital anomalies?

togaviridae

Chikungunya (CHIKV) belong to:

aedes mosquito

vector of CHIKV

Eastern and Western Equine Encephalitis Viruses

most severe of the arboviral encephalitis, highest case fatality rate

western equine encephalitis

Transmission occurs at a low level in the rural West - Birds and Culex tarsalis mosquitoes are involved in the maintenance cycle of the virus

St. Louis encephalitis virus

Most important cause of epidemic encephalitis of humans in North America

presence of infected mosquitoes

what is required for st Louis encephalitis?

west nile fever virus

Member of the Japanese B encephalitis antigenic complex of flaviviruses - Occurs in Europe, the Middle East, Africa, the former Soviet Union, Southwest Asia and, more recently, the United States - Detected in all 48 contiguous states

no

human vaccine for west nile virus?

older population

who does wes nile typically affect

Japanese B encephalitis virus

leading cause of viral encephalitis in Asia

adulthood

Seroprevalence studies indicate nearly universal exposure to Japanese B encephalitis virus by:

no

treatment for Japanese B encephalitis virus

asia

Several effective Japanese encephalitis vaccines are available in:

yellow fever virus

flaviviridae family, acute febrile yellow fever, vector mosquito, high mortality rate

liver and renal dysfunction and hemorrhage

severe cases of yellow fever and characterized by

no

is there antiviral drug therapy for yellow fever virus?

dengue virus

flavivirus, vector is mosquito

children

who does dengue hemorrhagic fever and shock syndrome typically affect

NO

Is there antiviral drug therapy for dengue?

fluid replacement therapy

dengue therapy?

dengvaxia

prevent severe dengue - attenuated virus vaccine

severe dengue

within Dengue administering vaccine to negative children predisposes the patient to:

already had virus

Give vaccine to 9-16 year-old that have:

enveloped spherical

what is the shape of bunyaviruses

segmented negative ssRNA

what is the genetic material genome for bunyaviruses

hantavirus (Sin Nombre virus): sheep

Which of the following Virus : Reservoir combinations is mismatched?