The study was conducted at four major international airports in Nigeria: Nnamdi Azikiwe International Airport (NAIA), Abuja; Mallam Aminu Kano International Airport (MAKIA), Kano State; Murtala Muhammed International Airport (MMIA), Lagos State and Port Harcourt International Airport (PHIA), Rivers State from Epi-week 11 to 14. These airports were selected because they were designated to be the only points of entry (POE) for international air travel into the country, as part of the country’s heightened surveillance against SARS-CoV2 before the country’s closure of all international airports to non-emergency and non-essential international air travel in Epi-week 14. MMIA and PHIA are located in Southern Nigeria, MAKIA in Northern Nigeria, while NAIA is located in the nation’s capital, in the heart of the country. (Figure 1). All four airports received flights from China in addition to other countries around the world.
The Port Health Services (PHS) Officers supported by residents and graduates of the Nigeria Field Epidemiology and Laboratory Training Program (NFELTP), staff of the NCDC and surge staff from state governments, screened all in-coming international air passengers especially those from countries with on-going community transmission of SARS-CoV-2 for symptoms of COVID-19 and history of contact. Non-symptomatic travellers from high-risk countries were categorized as persons of interest (POI). These POIs were advised to self-isolate for 14 days in addition to practising COVID-19 preventive measures.7 Symptomatic POIs were further evaluated to assess if they met the suspected case definition of SARS-CoV-2 and if they did, were tested to confirm their status. Persons of interest who did not meet the suspect case definition of COVID-19 were advised to self-isolate for 14 days as well as adhere to other recommendations by the NCDC. 7,8,23,24 These POIs were monitored through calls by the NCDC for COVID-19 symptoms.
Study design, study population, and sampling technique
This was a cross-sectional study in which participants were recruited prospectively. We included all adult passengers aged 18 years and above who had been categorised as POIs in the ongoing COVID-19 airport surveillance (all in-coming air travellers from countries with confirmed ongoing community transmission of SARS-CoV-2, all in-coming air travellers who have symptoms suggestive of SARS-CoV-2 and all in-coming air travellers who are febrile upon arrival) arriving by air through one of the designated airports. All symptomatic POIs were excluded from the study. The sample size was estimated using the using the Kish’s formula,25
$$n=\frac{ {{Z}_{\alpha }}^{2}pq}{{d}^{2}}$$
Where n = minimum sample size, Zα = The standard normal deviate set at 1.96 which corresponds to 95% confidence interval, p = The prevalence of willingness to adhere to public health preventive measure in incoming travellers from literature is 48%,13 q= 1 – p, d= Precision which at 95% Confidence interval is 5 %, with \(n\) approximately 384 respondents. After adjusting for a non-response rate of 35%,13 sample size was adjusted to 591. This was proportionately allocated to the four airports based on the relative volume of international passengers per airport.19 Each airport was allocated as follows: PHIA international wing: 17, MAIKA international wing: 23, NAIA international wing: 130, MMIA international wing: 421 respondents.
Study tool
A pre-tested semi-structured, self-administered electronic questionnaire created by the authors based on available literature on COVID-19 was used to collect information from the study participants. This questionnaire was created using the google form platform and hyperlinks shared to respondents through short message services (SMS), WhatsApp, or emails based on the preference of the POIs. Asymptomatic POIs were consecutively recruited, and hyperlinks sent until required number of responses was attained. The questionnaire consisted of sections on socio-demographic characteristics, recent travel itinerary, previous history of contact, knowledge of novel coronavirus symptoms and preventive practises, previous practise of COVID-19 preventive health measures, risk perception towards COVID-19 (perceived severity of COVID-19, perceived susceptibility to COVID-19,and perceived self-efficacy towards these preventive measures), self-rated health status and their willingness to practise certain public health preventive health measures within 14 days of arrival (self-observation for COVID-19 symptoms, early reporting of COVID-19 symptoms if observed by calling the NCDC national emergency numbers on COVID-19, staying at home, avoidance of contact with others, covering of nose and mouth if symptomatic) as well as perceived concerns regarding the preventive measures. The questionnaire was translated into simple Chinese using a professional translator as Chinese nationals constituted the majority of foreign nationals into Nigeria from high-risk countries. The Chinese version of the questionnaire was subsequently back translated to English by a postgraduate Chinese student to confirm its authenticity.
The questionnaire was pretested among 33 incoming international air travellers into Nnamdi Azikiwe International Airport (NAIA), Abuja before commencement of the study. The reliability of the tool was determined using Cronbach’s alpha. A Cronbach’s alpha of 0.75 was obtained for the willingness assessment scale while a Cronbach alpha of 0.72 was obtained for previous COVID-19 preventive practise scale. Those who participated in the pre-test did not participate in the main study.
Data quality assurance
Skip logics and compulsory questions were employed to limit incomplete entries. In addition, a test question to screen out symptomatic incoming travellers was added to ensure data quality.
Data management and Analysis
Data was extracted from the google drive database into Microsoft Excel 2016 where it was cleaned including the removal of duplicate entries. Data analysis was performed using Microsoft Excel 2016 and Epi Info version 7.2
Willingness to comply with the recommended public health measures based on the prevailing recommendation by NCDC and WHO was assessed using a ଁve-point Likert scale response which included ‘not at all willing,’ ‘a little willing,’ ‘moderately willing,’ ‘very willing,’ and ‘extremely willing’. In addition to ‘don’t know’ and ‘refused’ responses. The willingness to practise SARS-CoV-2 public health preventive measures recommended for asymptomatic POIs were assessed across five domains: Willingness to observe for symptoms of COVID-19 infection for 14 days after arrival; willingness to stay at home for 14 days after arrival, willingness to avoid contact with other people for 14 days after arrival, willingness to always properly cover nose and mouth if symptoms of SARS-CoV-2 develop within 14 days of arrival and their willingness to call approved national emergency numbers for COVID-19 if symptoms develop (NCDC’s national COVID-19 hot-line). A respondent was categorised as willing to practise any of COVID-19 public health measures if he/she was very willing or extremely willing to practise any of COVID-19 public health measures within 14 days of arrival. Knowledge of COVID-19 was assessed using 6 questions with a minimum score of 0 and a maximum score of 6. Those who scored 5 and above, out of 6, were categorised as knowledgeable of SARS-CoV-2 infection and preventive practices. Their pre-arrival practise of recommended preventive measures against SARS-CoV-2 was assessed using 3 questions (frequent hand washing with soap and water/ use of hand sanitizers, avoiding persons with symptoms suggestive of acute respiratory tract infections and avoiding of face touching) on a 5-level Likert scale ranging from ‘never’ to ‘always’. The scores were assigned as follows: ‘Never’ =1, ‘Rarely’ = 2, ‘Sometimes’ = 3, ‘frequently’ = 4 and ‘always’ = 5 for the past 2 weeks. Self-rated health status was assessed using a ten-point scale from poor to excellent.26 Those who indicated 7 to 10 as their perceived health status were categorised as having a good self-rated health status.26
Univariate, bivariate (chi-square) and multivariable analysis of data was carried out. Odds ratios (ORs), confidence intervals and P-values were computed. Willingness to adhere to the individual public health measures within 14 days of arrival were the dependent variables while sociodemographic characteristics, knowledge of novel coronavirus symptoms and preventive practises, previous practise of COVID-19 preventive health measures, self-rated health status, perceived self-efficacy, perceived severity, perceived susceptibility and concern for self/family were the independent variables. For multivariable analysis, variables with a P-value of less than 0.2 in the bivariate analysis were entered into the multivariable logistic regression model using the backward approach. The level of significance was put at 5% for the adjusted OR.
Ethical consideration
Ethical approval was obtained from the National Health Research Ethics Committee, Abuja with approval number: NHREC/01/01/2007-10-/3/2020. Written informed consent was obtained from all respondents and confidentiality was maintained at all times. To ensure data security, access to the database was limited to only those involved in data analysis. At the end of the questionnaire, respondents were given links to NCDC, WHO and CDC websites on COVID-19 preventive measures and what to do if symptoms developed. Government approved national emergency numbers to call on development of symptoms suggestive of the novel coronavirus was also attached at the end of the questionnaire.