Usutu virus

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Usutu virus
Virus classification Edit this classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Kitrinoviricota
Class: Flasuviricetes
Order: Amarillovirales
Family: Flaviviridae
Genus: Flavivirus
Species:
Usutu virus

Usutu virus (USUV) is a

dead-end host. First identified in South Africa
in 1959, the virus has caused outbreaks in birds across Europe since 1996. Nearly 50 cases in humans have been reported as of 2019, mainly in Europe. These are predominantly asymptomatic, but some people experience neurological symptoms.

History

USUV was first identified by Bruce McIntosh in

Old World blackbirds in Italy.[6]

Only two human cases have been identified in Africa, in 1981 and 2004, with one benign and one severe case described.

immunocompromised patient was infected, causing encephalitis.[7]

Immunohistochemistry (IHC) of USUV-uninfected (A, C) and –infected (B, D, F and F) blackbird organs using an USUV-specific murine monoclonal antibody.
(A) USUV-uninfected blackbird brain.
(B) USUV-infected blackbird brain showing a group of USUV-positive neurons (in red).
(C) USUV-uninfected blackbird heart.
(D) USUV-infected blackbird heart, USUV-positive cells are localized in the endocardium (in red).
(E) USUV-infected blackbird liver, disseminated USUV-positive Kupffer cells (in red).
(F) USUV-infected blackbird lung, disseminated USUV-positive cells (in red).

Virology

USUV has a diameter of 40–60 nm and is enveloped. The genome is a +-sense, single-stranded RNA of 11,064 nucleotides with a 5′ N7-methylguanosine-triphosphate cap. There is one open reading frame, which encodes a 3434-amino acid polyprotein. This is processed to generate eleven proteins: three structural and eight non-structural proteins. Replication occurs in the cytoplasm of the host cell.[3]The virus has eight lineages, five in Europe and three in Africa.[3]

Epidemiology and host range

USUV has been reported from several African countries including

Cote d'Ivoire, Morocco, Nigeria, Senegal, South Africa, Tunisia and Uganda,[1][3] as well as from Israel. Since 1996, it has also been found in European countries, including Austria, Belgium, Croatia, Czech Republic, France, Germany, Greece, Hungary, Italy, Serbia, Spain and Switzerland, and more recently the Netherlands, and was spreading across Europe in the late 2010s. Outbreaks are often simultaneous with those of the related West Nile virus.[3]

USUV's host range includes primarily

vector is one of several mosquitoes that bite birds, in Europe particularly Culex pipiens.[3] For example, a 2008–2009 survey of mosquitoes and birds in the Emilia-Romagna region of Italy detected USUV in 89 C. pipiens pools and in 2 Aedes albopictus pools, suggesting the possible involvement of A. albopictus in the virus cycle. The virus was also found in twelve wild birds, primarily Eurasian magpies (P. pica), hooded crows (Corvus cornix), and Eurasian jays (Garrulus glandarius).[8] In Africa multiple Culex species are involved, as well as several species of Aedes and other mosquitoes.[3]

Disease

Two cases of symptomatic infection in humans have been reported from Africa, with

skin rash but no neurological symptoms. In Europe, 46 infections were detected up to 2019; these were mainly asymptomatic, but neurological symptoms including encephalitis and meningoencephalitis have been observed.[3]

The virus is highly

pathogenic in birds, causing central nervous system symptoms, enlargement of the liver and spleen, and infiltration by inflammatory cells in a wide range of organs.[3]

References

  1. ^
    PMID 21767160
    .
  2. ^ McIntosh, Bruce M. (1985). "Usutu (SA Ar 1776), nouvel arbovirus du groupe B.". International Catalogue of Arboviruses. 3: 1059–1060.
  3. ^
    PMID 31364580
    .
  4. ISBN 978-3-030-11623-1
    .
  5. ISBN 978-0-671-20827-1
    .
  6. PMID 23347844
    .
  7. PMID 20070936
    .
  8. PMID 22666446
    .
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