A close look at a Culex mosquito. Photo: Muhammad Mahdi Karim/Wikimedia Commons, GNU FDL 1.2.
New Delhi: Some media outlets recently published sensational reports on a study conducted by scientists of the Indian Council of Medical Research (ICMR) in 2017 and 2018, and published in June this year, to say yet another virus could cause a new pandemic.
However, the tone and nature of the reportage, from calling it “another virus from China” to ICMR apparently raising an “alarm” over it, are in contrast to the study itself, which the authors say was conducted in advance to develop diagnostic tests against the virus. (The paper itself doesn’t include the words “alarm” or “warning”.)
The study’s paper is entitled ‘Proactive preparedness for Cat Que virus: An Orthobunyavirus existing in India’, and was published in the Indian Journal of Medical Research. It says the presence of the Cat Que virus (CQV) in Culex mosquitoes and pigs has been reported from China and Vietnam. Since Culex mosquitoes are widespread in India, the researchers determined “a need to understand the replication kinetics of this virus in mosquito models.”
Further, “As part of preparedness and to identify the presence of CQV in humans and swine,” they write that they undertook their study in order to “develop diagnostic tests”.
CQV is a virus of the genus Orthobunyavirus, which has 49 species and 19 serogroup complexes; CQV itself belongs to the ‘Simbu’ serogroup. The genus includes arboviruses that infect both humans as well as economically important livestock species. Humans can get infected with viruses of this genus, transmitted by mosquitoes. They include the Cache valley virus, which causes meningitis; the La Crosse virus, which causes paediatric encephalitis; and the Guaroa virus, which causes febrile (i.e. fever-associated) illnesses.
CQV was reportedly first isolated from mosquitoes in Vietnam in 2004 (Cát Quế is the name of a place near Hanoi, in North Vietnam). The authors write that a virus isolated from a jungle myna in 1961 in Karnataka was identified to be CQV in 2016. According to the study, the role of mosquitoes as vectors of the virus has been established, but the role of birds – either as hosts or vectors – had not been documented.
The authors then set out to study the susceptibility of three mosquito species to the virus, and also attempted to identify infections in humans and pigs. Pigs are the virus’s primary mammalian hosts, determined, among other studies, by one in 2005. The authors of a 2015 paper, corresponding to a study conducted in China, interpreted their findings to mean “CQV has formed a natural cycle in mosquitoes and pigs in the local area and may be associated with human and animal diseases.”
To quote from the ICMR paper at length:
Availability of vector, primary mammalian host (swine) and confirmation of CQV from jungle myna signifies the potential of this [virus] as a public health pathogen in India. This led us to develop molecular and serological tests for CQV, screening of host population (human and swine) and its replication kinetics in mosquitoes as a part of preparedness against the likely emergence of CQV.
Data showed that Indian mosquitoes … were susceptible to CQV. … Thus, mosquitoes were found to be a potential vector for CQV transmission to mammalian hosts. The diagnostic assays developed during this study could be used for rapid detection of CQV as part of vigilance for future CQV outbreaks.
These three species of mosquitoes are Aedes aegypti, Culex quinquefasciatus and Culex tritaeniorhynchus. “The real-time data depicted that the CQV multiplied in all three species of mosquitoes over a period of 12 days post-infection,” the paper reads.
The authors collected serological and molecular samples from 1,020 people who reported acute febrile illnesses between 2014 and 2017. These illnesses are the result of infections which cause fevers lasting longer than a week and which don’t have an identifiable cause. These samples were tested for the presence of CQV using real-time RT-PCR tests, and all of them were found negative.
At the same time, the scientists also collected 883 samples to test for antibodies against CQV. Of these, two from Karnataka tested positive.
The RT-PCR test looks for fragments of the virus’s gene in a given sample. Tests that check for antibodies are more indirect in that they suggest the virus’s presence based on the host’s reaction to it.
The authors of the ICMR study suggest that the presence of CQV antibodies in human serum samples and the replication capability of CQV in mosquitoes indicates a “possible disease causing potential” of the virus in the Indian scenario. “Screening of more human and swine serum samples using these assays [a procedure to determine the presence of a virus] is required as a proactive measure for understanding the prevalence of this neglected tropical virus,” they write.
The scientists also acknowledged some limitations of their study, including the fact that they could not avail sufficient quantities of positive serum samples. As a result, they could not perform a virus neutralisation test, which would have determined the virus’s specificity. “More human and swine samples need to be screened for further strengthening the outcome of the study,” they concluded.
According to them, the diagnostic tools developed in the study could be useful to detect CQV in human and swine populations in future.
An article in DNA India claimed that ICMR scientists had “found” the virus and constituted the study’s findings to be a “warning”. A Hindustan Times headline said the virus could be a “pandemic in India” (by definition, a pandemic is characterised by outbreaks in multiple geographical regions). An article in WION began “new virus found in China”.
All these articles, and others besides, have reported the ICMR findings together with the anxiety and uncertainty surrounding the ongoing coronavirus pandemic. Indeed, scientists have already reported that they expect climate change and the effects of industrialisation and urbanisation to precipitate more pandemics in future. And hyper-connectivity, economic inequality and unsustainable rates of resource extraction could exacerbate their effects.
However, sensationalist reports of scientists’ attempts to understand, and prepare for, future incidents could falsely heighten the sense of danger, trigger more panic and anxiety, and feed divisive narratives against China, and more broadly against Southeast Asian nations.