By Haruna Gimba
The Nigeria Centre for Disease Control (NCDC) and Nigeria Institute for Medical Research (NIMR) have released findings of household seroprevalence surveys conducted in Lagos, Enugu, Nasarawa and Gombe States.
A statement by chief executive officers of NCDC and NIMR, Dr. Chikwe Ihekweazu of NCDC and Professor Babatunde Salako of NIMR, said the survey was conducted between September and October 2020.
According to the statement, the surveys were designed to improve the estimate of the burden of COVID-19 infection in the country and provide a more detailed estimate of the extent of infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viruses, the virus that causes COVID-19.
It stated that blood samples were collected from over 10,000 individuals residing in a representative sample of households in the four states. “The blood samples were then tested for the presence of SARS-CoV-2 antibodies applying locally validated laboratory tests.”
It was learnt that individuals who provided blood samples also answered a brief questionnaire that enabled the study team to characterise factors related to positivity and identify which population groups were most affected.
“The survey findings released revealed that the prevalence of SARS-CoV-2 antibodies was 23 percent in Lagos and Enugu States, 19 percent in Nasarawa State, and 9 percent in Gombe State.
“This means that as many as 1 in 5 individuals in Lagos, Enugu and Nasarawa State would have ever been infected with SARS-CoV-2. In Gombe, the proportion is about 1 in 10,” the statement said.
The NCDC, NIMR added that the rates of infection are higher than those reported through the national surveillance system and reveal that the spread of infection in the states surveyed is wider than is obvious from surveillance activities.
“This is not surprising for COVID-19, given that a majority of those infected do not have any symptoms.
“Results of the survey further showed higher rates of infection among: males than females; 10 percent and 7 percent in Gombe and 21 percent and 17 percent in Nasarawa.
“Urban compared to rural and residents; 28 percent and 18 percent in Enugu and 23 percent and 19 percent in Lagos and persons aged 18-64 years. There were also variations across the local government areas (LGA) within the four states.
The survey team noted that these observations are in tandem with what had been reported by the NCDC based on the national surveillance system.
Dr Ihekweazu and Professor Salako added that in interpreting the results, the survey team noted that “SARS-CoV-2 emerged only one year ago and antibody response according to severity of infection and the duration of antibody persistence are not yet completely understood.”
“Given the high proportion of asymptomatic cases in Nigeria, the true seroprevalence of ever having infection may be underestimated in the survey if individuals infected early in the outbreak no longer had sufficient antibodies for detection when the survey was conducted.
The results from the survey show that a significant proportion of people in Nigeria are still at risk of SARS-CoV-2 infection and therefore, COVID-19. “It is very important that Nigerians continue to adhere to public health and social measures including regular handwashing, proper use of face masks and physical distancing.”
The United States Centers for Disease Control and Prevention (US-CDC), the University College London, supported by Bill and Melinda Gates Foundation, the University of Maryland, Baltimore (UMB), and the respective State Ministries of Health supported implementation of the survey.
“The survey is being expanded to more states with a priority to capture information from States in the North-West and South-South geopolitical zones which were not included in the initial round of surveys,” it added.