Initial viral load of a COVID-19-infected case indicated by its cycle threshold value of polymerase chain reaction could be used as a predictor of its transmissibility - An experience from Gujarat, India

Abstract

Background: Transmission dynamics of the infectious disease Corona Virus Disease - 19 (COVID-19) is yet to be understood fully. The study aimed at exploring whether quantitative viral load of COVID-19-infected case indicated by cycle threshold (Ct) value of real-time reverse transcription polymerase chain reaction could predict about transmission pattern in the community. Materials and Methods: An observational study was conducted involving 1976 individuals, suspected to be suffering from COVID-19 and contacts, of laboratory confirmed cases from selected districts of Gujarat, India. A total of 138 persons were detected to be positive. Weekly positivity showed an overall increasing trend during the studied weeks. It was observed that only 7% had high, 9% as moderate and rest, 84% had low viral load based on Ct values of real-time RT-PCR. Results: Most secondary cases clustered around index cases with high viral load whereas fewer secondary cases clustered around index cases with low viral load. Each index high viral load case transmitted an average of 6.25 secondary cases whereas the same of low viral load transmitted an average of 0.8 case. Conclusion: If cases with higher viral load are selectively isolated on detection from the rest of the community along with contact tracing of all individuals, who came in contact with them during the previous 5 days, the quantum of transmission will reduce subsequently. Moreover, health-care workers often get infected while working, probably due to the fact that they often handle cases with higher viral load. The Ct value of all may be provided along with test report to safeguard everybody's health including health-care workers.

COVID control strategy–-is there any light at the end of the tunnel?

“…Recently, one public health research institute based in Ahmedabad had established and suggested a public health control strategy of COVID-19 infections based on their pilot research work. [ 4 5 ] The strategy stresses upon the rationality that, the viral load could be an important determinant in spreading infections in the community. Individuals with high viral load are super-spreaders - they take the centre stage in person to person transmissions of coronavirus.…”

“…But cases started declining visibly following implementation of viral load/Ct-based segregation and management following adoption of it by Government of Gujarat as per suggestion of ICMR-National Institute of Occupational Health on experimental basis. [ 5 ] It may be noted that it was restricted to Ahmedabad district only initially to assess its impact. There was a plan to implement it all over Gujarat state if proved to be effective.…”

“…Hence, we need to concentrate on some effective public health strategy which is already established (as evidenced by data) such as the Ahmedabad Model for control of COVID-19. [ 4 5 ] It appears, if we further delay in taking actions about it or if we turn a blind eye on it, cases will keep on increasing exponentially, resulting in high mortality and morbidity; and the country will eventually have to pay a heavy price due to lack of an effective action taken by us.…”

Control of an Epidemic of SARS-CoV-2 by Assessing Transmissibility of Its Infected Cases in Absence of a Suitable Vaccine

“…The study revealed that only 7% of the infected ones carried high viral load, while another 9% of the infected population had moderate viral load and rest 84% were carrying low viral loads as per community distribution was concerned. [19] Viral load was categorised as high when cycle threshold value = <24, moderate = 24 to <31 and low = 31 & above (Figure 1).…”

“…Further, the results might be extended to emphasise the need for sterilising such fomite surfaces to prevent viral transmission. Considering the positive relation between viral load and the disease contagiousness [19,23,24], the sources (spreader/positive subjects) with high viral load should be treated with great care, i.e., health care facility with possibly high viral load should adopt maximum precautionary measures. The study indicates that fomites could play an important role in the disease transmission in addition to human contact, particularly at COVID-19 care facilities, market places etc.…”