In a study conducted in Zanzibar, researchers have shared insights on the extent of COVID-19 exposure among key population groups during the early stages of the pandemic. Spanning from March to December 2020, the study focused on healthcare workers, school children, and market-goers.

Published in the Advances in Infectious Diseases journal, the study provides valuable insights into the COVID-19 landscape in Zanzibar laying a foundation for future research in understanding the dynamics of the pandemic in the region.

“This seroprevalence study is the first to collect blood samples and analyze SARS-CoV-2 exposure among healthcare workers, school children, and people who attend markets in Zanzibar during the COVID-19 pandemic.”

“Our objectives were to analyze the total antibodies from selected higher-risk population groups to determine the magnitude of SARS CoV-2 exposure,” they added.

Ifakara scientist as lead co-author
The scientists involved in the study include lead authors Ame Masemo from Zanzibar Health Research Institute and Solomon Mwakasungula from the Ifakara Health Institute.

They worked alongside colleagues from the National Institute for Medical Research Muhimbili Centre, Binguni Public Health Laboratory and Mnazi Mmoja Hospital both in Zanzibar, and the Royal Free Hospital Campus, University College London, UK.

COVID-19 information gap in Zanzibar
According to the scientists, the study also aimed to fill the data void of COVID-19 exposure in Zanzibar which was scarce since the onset of the pandemic. 
Through blood sample collection and surveys conducted across Unguja and Pemba Islands in Zanzibar, they identified the magnitude of the virus exposure and its dynamics within the population.

“The spread of infections in a population depends heavily on social interactions and population density, therefore, assessing the proportion of potentially protected individuals in populations with different levels of exposure is crucial,” reported the scientists adding, “As recommended by WHO, measuring the extent of SARS-CoV-2 seropositivity could help to understand the rate of disease transmission over time.”

Unveiling the extent of exposure
The study, which focused on populations with high-risk occupations and social interactions, revealed an overall SARS-CoV-2 seroprevalence of 33% across all age groups with individuals in the 40 - 49 age bracket exhibiting a higher seroprevalence than other age groups.

From the 707 participants enrolled in the study, significant disparities were observed in the exposure rate across different groups. Notably, individuals who frequented markets exhibited the highest seroprevalence of 42.9%, followed by students (28.9%) and healthcare workers (27.3%).

Factors such as crowded marketplaces and schools likely contributed to higher exposure rates among these groups, noted the scientists.

“Exposure in these groups might have been influenced by infection and prevention strategies taken by the government, as well as shopping behavior, school overcrowding, and population density in urban settings,” they wrote.

Moreover, the study highlights the impact of urban living on SARS-CoV-2 transmission, whereby urban residents faced significantly higher odds of seropositivity than those residing in rural areas. 

Digging deeper into the data, the scientists concluded that these findings align with global trends that identify urban settings as hotspots for virus transmission, suggesting potential links between population density, urban living, and COVID-19 transmission dynamics.

Identifying common symptoms
Common symptoms reported among participants with past SARS-CoV-2 infections included a runny nose, headache, and cough. The most frequently reported symptom was a runny nose, reported by 18.8% of the study's participants. 

“About 6.8% of participants reported having contacted a person with confirmed COVID-19 disease. A runny nose (18.8%) was the most frequently reported SARS-CoV-2-related symptom followed by 16.4% of participants experiencing a headache and/or a cough (13.9%).” 

Impact on vulnerable groups
The scientists believe these findings underscore the vulnerability of specific groups, emphasizing the importance of targeted interventions to mitigate COVID-19 spread within communities.

The significance of the study for public health interventions was also underlined. By identifying exposure patterns across different populations, targeted strategies can be developed to reduce the spread of COVID-19 within communities, protecting vulnerable populations.

What should be done?
The scientists recommend “further well-designed, longitudinal studies” to deepen the understanding of SARS-CoV-2 exposure and transmission at the population level and assess the effectiveness of control measures.

“As the findings of this study cannot be generalized to the whole population, a larger, systematic, population-based serosurveillance study, encompassing prospective surveillance, is critically needed to enhance understanding of exposure and infections in the general population and monitor the trend of infections in Zanzibar.”

Scientists involved in the study
The scientists involved in the study include Ame Masemo from Zanzibar Health Research Institute and Solomon Mwakasungula from Ifakara Health Institute – both lead authors of the study. 

They worked along with colleagues Khamis Kheir, Nahya Khamis, Khamis Salim and Mayassa Ally – also from Zanzibar Health Research Institute along with, Irabi Kassim, Sarah Mswata, Theckla Kazimoto and Honorati Masanja, from Ifakara Health Institute.

Others included Erick Mgina from the National Institute for Medical Research Muhimbili Centre, Bihila Bakar from Binguni Public Health Laboratory in Zanzibar, Kibwana Omar from Mnazi Mmoja Hospital, Stone Town, Zanzibar and Linzy Elton from Royal Free Hospital Campus, University College London, UK.

Read the full publication here.