Tanapox (a virus from the genus ''

Yatapoxvirus ''Yatapoxvirus'' is a genus of viruses, in the family ''Poxviridae'', in the subfamily ''Chordopoxvirinae''. Monkeys and Baboon, baboons serve as natural hosts. There are two species in this genus. Diseases associated with this genus can cause H ...

'') was first seen among individuals in the

flood plain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...

of the Tana River in

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

during two epidemics (1957 and 1962) of acute febrile illness accompanied by localized skin lesions.

Signs and symptoms

The incubation period in human cases remains unknown, but in a person who underwent voluntary inoculation,

erythema Erythema (, ) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation. Examples of erythema not associated with pathology inc ...

and central thickening appear by the fourth day. Most patients present a mild pre-eruptive fever that lasts 3–4 days, severe headaches and backaches, and often itching at the site where the skin lesion develops. There is initially a small nodule, without any central abrasion. This small nodule soon becomes papular and gradually enlarges to reach a maximum diameter of about 15 mm by the end of the second week of infection. The draining

lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...

s are also enlarged and tender from about the fifth day following the appearance of the skin lesion. The lesion remains mostly nodular but, ulcerates during the third week and then gradually heals within five to six weeks, leaving a scar. In Kenya, the lesions were almost always solitary and were found on the upper arm, face, neck, and truck. Conversely, in

Zaire Zaire, officially the Republic of Zaire, was the name of the Democratic Republic of the Congo from 1971 to 18 May 1997. Located in Central Africa, it was, by area, the third-largest country in Africa after Sudan and Algeria, and the 11th-la ...

, 22% of patients had multiple lesions, usually two or three. The maximum number of lesions seen in one patient was ten. In the case of Zairian patients, the lesions were mostly found on the lower limbs, with a couple of patients reporting lesions on the upper limbs, trunk, and head.

Histopathology

Tanapox virus in humans produces increased thickening of the epidermis with extensive degeneration of the prickle cell layer. The

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

of the swollen epidermal cells is filled with large,

eosinophilic Eosinophilic (Greek suffix '' -phil'', meaning ''eosin-loving'') describes the staining of tissues, cells, or organelles after they have been washed with eosin, a dye commonly used in histological staining. Eosin is an acidic dye for stainin ...

, pleomorphic, B-type inclusion bodies. Nuclei of infected cells are also swollen, with

chromatin Chromatin is a complex of DNA and protein found in eukaryote, eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important r ...

being concentrated at the nuclear periphery.

Epidemiology

Human tanapox has been mostly documented in

and

, but it is believed to occur much more widely throughout tropical Africa. All age groups and both sexes appear to be affected by this virus. During the Kenyan epidemics of 1957 and 1962, cases of tanapox were reported more frequently among persons who worked or played close to the river. As a result of this, researchers concluded that tanapox is most likely a

zoonosis A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a virus, bacterium, parasite, fungi, or prion) that can jump from a non-human vertebrate to a human. When ...

. However, neither the reservoir host nor the mode of transmission from wild animal to human is known. It is hypothesized that tanapox virus may be transferred from monkeys or another reservoir host to humans by infected

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s that act as mechanical vectors. Only one case of human to human transmission has been reported.

References

External links

{{Zoonotic viral diseases