Scientists discover two new viruses in people in Tocantins and Amapá

Publicação: 11 de April de 2020

One of the viruses belongs to the genus Ambidensovirus and the other to the genus Chapparvovirus

Understanding the origin of these two viruses is likely to involve similar metagenomic sequences from mosquito and wild animal viruses

A genetic material analysis technique applied to 781 blood samples collected in Brazil was able to identify the presence of two new viruses in the blood of patients with symptoms similar to dengue or zika, such as fever, headache and reddish patches on the skin. One, which belongs to the genus Ambidensovirus, was found in a sample collected in Amapá, and the other, which belongs to the genus Chapparvovirus, in a sample from Tocantins. The results of the survey Plasma virome of 781 Brazilians with unexplained symptoms of arbovirus infection include a novel parvovirus and densovirus in PLOS ONE magazine in March.

Professor Antonio Charlys da Costa, one of the authors of the study, explains that it is not possible to say 100% for sure that these new viruses were what caused the symptoms in patients – for this, larger and more complex studies would be necessary – however, no other agent was found that could explain the clinical picture. “These viruses are very distant relatives of the parvovirus B19, which can cause symptoms similar to arboviruses, and scientific articles have already been published reporting the B19 epidemic hidden behind the dengue epidemic”, he says. Still according to the researcher, the important thing is that there may be other pathogens overshadowed by epidemics of known agents. It is estimated that there are over 100 million different species of virus and currently we know about less than 20 thousand species of virus. “In a country with continental dimensions, biodiversity, anthropic activity, and a precarious basic sanitation system as in Brazil, we have a perfect scenario for the emergence of pathogens”, he adds.

For Dr. Eric Delwart, a researcher at the Vitalant Research Institute (United States) and project supervisor, surveillance of viruses in sick humans is necessary to identify those that pose a potential risk of emergence. “Fever and other symptoms of viral infections make it possible to sample patients who may be infected with previously unknown viruses”, he says. Professor Delwart, points out that there is currently no evidence that these discovered viruses are pathogenic. “They were found in only one febrile patient each. These viruses may reflect the many mosquito viruses that people are exposed to, which are not yet adapted to be efficiently transmitted and therefore do not spread widely. One virus belongs to a group capable of replicating in mammals, while the other is currently believed to replicate only in invertebrates ”, he points out.

Both viruses belong to the Parvoviridae family. Among the best known related viruses are parvovirus B19 and bocaviruses. The new chapparvovirus belongs to a group of viruses known to infect vertebrates. The ambidensovirus, on the other hand are distinguished by their ability to infect insects. “The two new viruses share only 34% sequence similarity with known viruses indicating that their recent ancestor, and therefore original animal hosts, are not known. Further studies are needed to determine whether these are rare single events with no onward human transmissions or are more common infection that may be pathogenic and spreading.

Asked what could explain the presence of an ambidensovirus in humans, viruses that had only been described in insects, crustaceans and other invertebrates, Dr. Costa admits that any kind of speculation about the contamination of the individual by this virus is difficult, but we have already found another virus of this same group in cerebral spinal fluid of an individual with encephalitis.

Identifying new species and next steps

The samples were previously tested by PCR for numerous known pathogens (Enterovirus, Flavivirus, Alphavirus, Parvovirus B19) and the negative samples were then subjected to viral metagenomics. This technique consists of identifying all viral nucleic acids in a biological sample, using sequence similarity searches against known organisms including all known viruses. “Doctors Charlys da Costa and Professor Ester Sabino, from the Institute of Tropical Medicine (IMT-USP), were instrumental in organizing the acquisition, testing and analysis of data and continue to collect more recent samples of unexplained febrile cases. Molecular surveillance of these unexplained cases of fever is a form of early detection of emerging viruses if performed almost in real time on a much larger scale. Steady funding from national and international sources is required to maintain and expand these surveillance programs”, acknowledges Dr. Delwart.

Tests on samples from other states (Alagoas, Paraíba, Mato Grosso do Sul, Rio Grande do Norte, Rio Grande do Sul, Maranhão, Piauí and Espírito Santo) are also being performed”, reveals Dr. Costa. According to Dr. Delwart, it is necessary to analyze a much larger group of patients with unexplained fever and test for viral antibodies to get a better idea of their prevalence and possible association with the disease. “Therefore, there is currently no indication of viral dissemination for these two new viruses, but there is also very little relevant data”, he notes.

However, as the researchers seek only the presence of viral nucleic acid it is difficult to say whether there are more cases or not, but with serological tests it will be possible to verify the presence of antibodies in the population. “We describe never previously described viruses in human plasma in Brazil, so this should draw attention to the viral diversity we have, warns Dr. Costa.

Finally, Dr. Delwart recalls that coronavirus reminds us of the speed at which viral outbreaks can spread. “Avoiding contact and consumption of wild animals is critical. Avoiding exposure to mosquitoes is more difficult for many. Therefore, surveillance of this population exposed to arboviruses is important for the early detection of viruses, in order to monitor their prevalence, dissemination and association with disease. Our studies indicate that unexpected viruses in the bloodstream of febrile humans exposed to mosquitoes may not be rare occurrence. Poor adaptation of these viruses to additional human transmission may be what prevents their spread. Understanding the origin of these two viruses is likely to involve similar metagenomic sequencing of mosquitoes and wildlife”, he concludes.