Zika: American subtype revealed to have the highest virulence activity in mice

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Findings from the Japanese National Institute of Infectious Disease (Tokyo, Japan) comparing subtypes of Zika from America, the Pacific and Southeast Asia have revealed the American subtype exhibits the highest virulence activity amongst the virulence-contributing abilities tested.

Published in PLOS Neglected Tropical Diseases, the paper analyzes both in vitro and in vivo growth-rates of each subtype, measuring viral loads and assessing the damage caused to the testis of infected mice. This allowed comparative evaluation of tested characteristics that are known to contribute to virulence, and consolidated previous work that had eluded to the possibility of a distinction in the pathogenicity profiles of each subtype (American, Pacific and Southeast Asian).

The American-subtype, namely PRVABC59, was found to have the highest growth potential, and was deemed the most damaging to the testis when measured 6 weeks post-infection. The ZIKV/Hu/NIID123/2016 (NIID123) subtype, more simply known as the Southeast Asian subtype, displayed the lowest growth ability out of the three tested; after 2 weeks, male mice infected with this subtype had the lowest abundance of infectious particle and viral RNA in the genital tract. The Pacific, ChibaS36, strain resulted somewhere in between.

This research may give answers as to why or how Zika has been able to disseminate eastwards from Africa and Asia in recent years, causing epidemics in the Americas.

“These results raise the possibility that ZIKV have acquired elevated proliferative capacity and pathogenicity during the process of the virus spreading from Southeast Asia to the Americas through the Pacific Islands,” commented researchers from the Japanese National Institute of Infectious Disease (Tokyo, Japan).

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Source: Kawai Y, Nakayama E, Takahashi K et al. Increased growth ability and pathogenicity of American- and Pacific-subtype Zika virus (ZIKV) strains compared with a Southeast Asian-subtype ZIKV strain. PLOS Negl. Trop. Dis. 13(6), e0007387 (2019).

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