Exposure to Covid-19 Reached 40% Among Some Cape Town Residents. Could it be that a Significant number of South Africans Have Been Exposed to Covid-19?

According to a Bloomberg article, a seroprevalence study among people who visited public health facilities for antenatal care and routine HIV tests in the Cape Town area found that 40% of respondents had antibodies against the coronavirus.
Could this be an indication of a much wider exposure rate nationally? What could this mean for the future of containing the spread of Covid-19 in South Africa?