SA scientists to explore asymptomatic spread of the Covid-19 virus in the country

  • Asymptomatic carriers of the new coronavirus may play a critical role in viral transmission
  • A new SA study will investigate the extent of asymptomatic spread in SA households
  • It will include participants in both rural and urban communities

A South African study is underway to assess how many people in individual rural and urban households in the country are becoming infected with SARS-CoV-2, the virus that causes Covid-19 disease.

To date, there is little information about the relative rate of transmission of the virus between rural and urban areas.

Vital questions

The study will focus on transmission of the virus via asymptomatic (producing or showing no symptoms) people, and how the virus interacts with other pathogens.

Named the PHIRST-C study, it will be led by Professor Cheryl Cohen, Professor of Epidemiology of the Wits School of Public Health and Head of the Centre for Respiratory Disease and Meningitis (CRDM) at the National Institute for Communicable Diseases (NICD) in the National Health Laboratory Service (NHLS) in South Africa.

“The study will help answer vital questions about how common asymptomatic infection is and how people who are infected with SARS-CoV-2 – but who remain asymptomatic – transmit the virus compared to those who do have symptoms,” said Cohen in a news release.

A scientific brief by the World Health Organization (WHO) dated 9 July, explains that the true extent of asymptomatic infection in communities remains unknown, but that the distinction between symptomatic and asymptomatic spread of the virus is important when developing public health strategies to control transmission. 

Cohen added that the study will also look at the role of children in virus transmission – an important observation now that schools have reopened.

Insights into rural infections

Individuals from communities in Mpumalanga will partake in the study. These communities also form part of the research institute in Agincourt (situated in the province), a health and socio-demographic surveillance system. 

According to the news release, Agincourt is a major research endeavour at Wits University’s rural campus in Bushbuckridge, which has run longitudinal studies and intervention trials in the community for over 25 years.

“Meeting the challenge of Covid-19 in rural South Africa is critical to the national response, now more than ever, as the pandemic approaches its rural peak,” said Professor Kathleen Kahn, who will be running the PHIRST-C study in Agincourt.

Kahn added: “Doing so effectively demands a deep understanding of how virus transmission differs among rural families and communities – exactly what PHIRST-C is designed to achieve.”

How the study will run

Participants will be tested twice weekly for SARS-CoV-2 until the end of 2020. They will also be asked about the presence of Covid-19 symptoms at each visit. The study will incorporate two different methods in order to estimate the burden of infection: polymerase chain reaction (PCR) tests and serosurveys.

PCR tests are used to detect the presence of viral genetic material directly, and the serosurveys will investigate the presence of antibodies and answer critical questions related to the body’s immune response to the virus, and the duration of the immune response.

“Serology results from this study may help to answer some outstanding questions related to Covid-19 immunity, for example, the level of antibodies needed to provide protection against reinfection as well as the rate of asymptomatic infection in South Africa,” said Professor Lynn Morris, interim Executive Director of the NICD and a Full Research Professor at Wits University.

Although research on the protective role of antibodies against the new coronavirus is ongoing, it is still unclear to what extent these antibodies "resist" infection. Researchers will, therefore, focus their efforts on using the serosurveys to estimate the burden of viral infection in these communities.

RSV and influenza testing to occur simultaneously

Since the PHIRST-C study builds on a cohort monitored from 2016 to 2018, which estimated the burden and household transmission of Respiratory Syncytial Virus (RSV) – a respiratory virus that infects the lungs and breathing passages – and influenza (flu), researchers will also conduct testing for RSV and flu during this period to help understand the interaction of these viruses, should they circulate in the communities at the same time.

“Obtaining more information from settings outside of large metropolitan areas is important,” explained Dr Neil Martinson, Chief Executive Director in the Wits Perinatal HIV Research Unit at Baragwanath Hospital, and Principal Investigator in the PHIRST-C study in Jouberton Township.

“This study will provide more understanding of the impact and transmission of Covid-19 in peripheral townships where health services, including Covid-19 testing sites, are not as available as in large cities; where household members are less likely to be employed; and where they are less likely to be able to safely self-isolate or self-quarantine,” Martinson added.

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