Is it time to review the concept of viruses?

Susana Fares Mazloum

In Brazil, scientists have recently discovered a new genus of viruses. The discovery has caused many uncertainties and has lead scientists in the area to question whether it will be necessary to rethink the concept of what exactly viruses are.

Is it time to review the concept of viruses?

The debate initiated due to the fact that this new discovery of the now called Tupanvirus, in homage to the God of the Guarani mythology Tupã, is among the largest viruses discovered. According to the researchers, it is so large that it can be observed in a common optical microscope. Impressively, it also contains more capacity to produce proteins than any other virus ever registered in history. In other words, its genetic complexity makes it unique when compared to other types.

tupan
The Tupanvirus discovered in Brazil. Credit: Jônatas Abrahão / Nature Communications

Its characteristics place the genus Tupanvirus in the Mimiviridae family, in which Amoeba and other protists serve as natural hosts. The family was created after the discovery of the Mimivirus in 2003; at the time, the Mimivirus was considered to be the virus with the largest capsid diameter–the envelope of protein origin that protects and facilitates the proliferation of the virus. Before this classification, a virus was completely separated from ‘living’ creatures. Their inability to synthesize proteins was one of the reasons scientists excluded them from the ‘cell life’ classification. This theory is now put to the test since genome sequencing has shown that the genetic chains of Tupanvirus not only have all the genes necessary for the production of protein but also 30% of its genome is unknown.

Researchers have also found another distinctive feature: the Tupanvirus has a structure that resembles a tail, the function of which is still unclear. The virus was found not to be a threat to humans, but its simple existence can change the direction of what science had stated as facts regarding the concept and classification of viruses.

The discovery of the Tupanvirus has provoked doubt in the scientific community. It raises contradictions to all of the information we had about viruses that we thought were fact.  Well, isn’t that what science is all about?

Nature Communicationsvolume 9, Article number: 749 (2018)
doi:10.1038/s41467-018-03168-1

Edited by: Kaylynn Crawford and Karen Yung