Factors associated with contracting Severe Acute Respiratory Syndrome Corona Virus type-2 in Norton Town, Zimbabwe, 2021: a case-control study

Memory Chimsimbe¹, Pride Mucheto², Notion Tafara Gombe³, Emmanuel Govha¹, Tsitsi Patience Juru^1,&, Maurice Omondi⁴, Mufuta Tshimanga¹

 

¹Department of Primary Health Care Sciences: Family Medicine/ Global and Public Health Unit, University of Zimbabwe, Harare, Zimbabwe, ²Department of Oral Health, University of Zimbabwe, Harare, Zimbabwe, ³African Field Epidemiology Network, Harare, Zimbabwe, ⁴African Field Epidemiology Network, Nairobi, Kenya

 

 

^&Corresponding author
Tsitsi Patience Juru, University of Zimbabwe, Department of Primary Health Care Sciences, Global and Public Health, Harare, Zimbabwe. tsitsijuru@gmail.com

 

 

 

 

Corona Disease 2019 (COVID-19) is a disease caused by the novel Severe Acute Respiratory Syndrome coronavirus-2 (SARS Cov-2) virus that originated in China and has spread globally [1]. The COVID-19 pandemic has negative effects on medical systems, societies, and economies worldwide [2]. COVID-19 is mostly spread by respiratory droplets released when people talk, cough, or sneeze or by touching a surface or object that has the virus on it and then touching their own eyes, nose and mouth [1,3]. Common signs of the infection include respiratory symptoms, fever, cough, shortness of breath and breathing difficulties. In more severe cases, the infection can cause pneumonia, severe acute respiratory syndrome, kidney failure and even death [4]. World Health Organisation (WHO) declared COVID-19 a disease of Public Health Emergency of International Concern (PHEIC). In response to this, globally countries have to put in place several COVID-19 prevention and containment measures to control the pandemic [5,6]. COVID-19 accounted for an excess of three million deaths globally in 2020 [7]. As of the 25th April 2021, globally there were 146,067,511 cases and 3, 092,497 deaths. Africa reported 3. 274,714 cases and 81,870 deaths. Zimbabwe reported 38, 064 cases and 1,556 deaths [8].

 

Zimbabwe developed the national preparedness and response plan for COVID-19 to minimize morbidity and mortality resulting from COVID-19 and associated adverse socio-economic impact [9]. Zimbabwe declared the COVID-19 disease a national disaster on the 18th of March 2020 [10]. On the 30th of March, a nationwide lockdown was instituted which banned the unnecessary movement of people whilst ensuring continuity of essential services. Periodic reviews of lockdown measures were done in 2020 [11]. The government of Zimbabwe instituted the second level four lockdown in January 2021 which restricted the movement of people and enforcement of public health prevention measures to contain the pandemic [12].

 

Norton Hospital recorded a total of 120 COVID-19 cases and 8(6.7%) deaths from the 28th of December 2020 through 6 January 2021. There was a rapid increase in the cases when contact tracing was intensified. The cases included 28 health care workers from the two local authority health facilities in Norton Town. Community awareness campaigns and health education on SARS-CoV-2 preventive and control measures such as self-quarantine, home or hospital isolation, contact tracing, use of face mask in public, social distancing and hand hygiene were conducted to control the outbreak, however, the cases continued to increase. We verified the COVID-19 outbreak by performing Reverse-Transcription Polymerase Chain Reaction (RT-PCR) for SARS CoV-2 from nasopharyngeal swabs among the clients who presented to the hospital. A line list was created for the cases. The line list captured the following information, name of the patient, physical address, age, date of onset of symptoms, history of travel outside the country, type of laboratory investigation done, type of treatment given, and the outcome. A preliminary descriptive analysis was conducted. Based on descriptive statistics, we hypothesised that there was no association between staying in high-density suburbs and contracting SARS-CoV-2.

 

To prevent and control SARS-CoV-2 infection among residents of an urban town, stakeholders and the Ministry of Health and Child Care must be informed by evidence-based research on the factors associated with contracting SARS-CoV-2. There have been extensive studies worldwide on SARS-CoV-2. However, there are limited published studies investigating factors associated with contracting SARS-CoV-2 infection in Zimbabwe. Understanding factors associated with contracting SARS-CoV-2 was critical for drafting tailor-made interventions to control the current outbreak and prevent future outbreaks in similar settings We investigated the risk factors for contracting SARS-CoV-2 in Norton Town and came up with evidence-based recommendations on prevention and control measures.

 

 

Study design

 

We conducted a 1:1 unmatched case-control study among residents of Norton Town, 2021

 

A case was defined as a person who resided in Norton Town two weeks before a SARS-CoV-2 RT-PCR positive result, with or without symptoms from 28 of December 2020 through 25 January 2021.

 

A control was defined as a person who resided in Norton Town two weeks before a SARS-CoV-2 RT-PCR negative result from 28 December 2020 through 25 January 2021 and staying in the same residential suburb with the case

 

Study setting

 

The study was conducted in Norton Town which is located 40 kilometres to the west of Harare along the Harare-Bulawayo highway. Norton Town serves a population of 48, 064 [13]. Norton Town has low, medium and high-density housing units. There are 13 urban wards, one hospital, two clinics as well as eight private clinics. Some residents of Norton Town commute daily for work to Harare, Chegutu Town and Selous.

 

Study population

 

The study population were people regardless of age and sex, who resided in Norton Town, two weeks before being tested for SARS-CoV-2 from 28 December 2020 through 25 January 2021.

 

Inclusion criteria

 

A person who tested positive for SARS-CoV-2 based on an RT-PCR with or without symptoms from 28 December 2020 through 25 January 2021, was a resident of Norton Town and consented to participate in the study (cases).

 

A person who tested negative for SARS-CoV-2 based on an RT-PCR from 28 December 2020 through 25 January 2021, was a resident of Norton Town and consented to participate in the study (controls).

 

Exclusion criteria

 

A person who tested positive for SARS-CoV-2 based on an RT-PCR with or without symptoms from 28 December 2020 through 25 January 2021, was not a resident of Norton Town or did not consent to participate in the study (cases).

 

A person who tested negative for SARS-CoV-2 based on an RT-PCR from 28 December 2020 through 25 January 202, was not a resident of Norton Town or did not consent to participate in the study (controls).

 

Sample size determination

 

We calculated sample size using the Fleiss formula in stat cal embedded in Epi info 7.2.4.0 assuming that the risk of SARS-CoV-2 was lower in those who wore face masks all the time with an odds ratio of 0.23, 24.1% exposure in controls in a study by Doung-ngern et al. (2020) in Thailand [14] at 95% confidence interval,80% power, 10% non-response rate.

 

A minimum sample size of 87 cases and 87 controls was calculated. However, to increase the power of the study a sample size of 100 cases and 100 controls were reached.

 

Sampling technique

 

Sampling of cases

 

Norton hospital COVID-19-line list was used as the sampling frame for selecting the cases. From a line list with 188 cases from 28 December 2020 through 25 January 2021, we enrolled 100 cases using simple random sampling. We used random numbers that we generated using the RANDBETWEEN function in Microsoft Excel.

 

Sampling of controls

 

We allocated numbers to the 194 persons in the laboratory register who tested SARS-CoV-2 RT-PCR negative from 28 December 2020 through 25th January 2021. We enrolled 100 controls using simple random sampling. We used random numbers that were generated using the RANDBETWEEN function in Microsoft Excel.

 

Data collection

 

We pretested our tool by administering 10 questionnaires to five cases and five controls who were not included in the study. We modified the few unclear questions. The pre-tested interviewer-administered questionnaire was used to collect data from both the cases and the controls. Interviews were held at the household level and at workplaces for recovered cases who were not at home during the data collection period. Data on demographics, knowledge of COVID-19 and factors associated with contracting SARS-CoV-2 was collected.

 

Data analysis

 

Epi info 7.2.4.0. statistical software was used to process the data and generate frequencies, proportions, univariate analysis. Odds ratios and their corresponding 95% confidence interval at 0.05 significance level were generated on bivariate analysis. Stratified analysis was performed to assess for possible confounding and effect modification. Forward stepwise multivariate logistic regression was carried out to determine independent factors associated with contracting SARS-CoV-2. All variables with a p-value less than or equal to 0.25 were included in the model.

 

Availability of data and materials

 

The data sets generated and analysed during the current study are available from the corresponding author on reasonable request.

 

Ethical considerations

 

Permission to conduct the study was obtained from the Provincial Medical Director of Mashonaland West, the District Medical Officer of Chegutu district, the Medical Officer of Health for Norton hospital and the Health Studies Office. The Institutional Review Board (IRB) for Mashonaland West Health Directorate reviewed the study protocol and approved the study.

 

Confidentiality was maintained throughout the study by not including participant names on the questionnaire. Since patients were tracked using medical records from the health facility, to ensure confidentiality, interviews were conducted after confirming the right candidate through producing a national identity card. Interviews were conducted in private and well-ventilated areas to encourage participants´ participation. Written informed consent and assent adapted from the Medical Research Council of Zimbabwe was obtained from the study participants. The written informed consent was kept separate from the questionnaires to avoid linking the responses to the participants. Hard copies of the questionnaires were kept in a lockable cabinet. Soft copies of the same information were kept in a password-protected folder and were only accessible to the researchers. Social distancing, hand hygiene and the wearing of a face mask covering the nose and mouth were maintained to protect the participants during the COVID-19 pandemic.

 

 

Demographic characteristics

 

A total of 100 cases and 100 controls were recruited. Fifty six 56(56%) of the cases and 68(68%) of the controls were aged between 25 to 49 years. Sixty seven percent (67%) of the cases and 72 (72%) controls were females. The majority 90 (90%) of cases and 91(91%) of the controls attained secondary education and above Table 1.

 

Bivariate analysis

 

We noted significant risk for contracting SARS-CoV-2 infection among participants who were 25 years of age and above (OR 3.32; 95% CI 1.33−8.26), who were employed (OR 1.77; 95% CI 0.99−3.19), who were asthmatic (OR 4.04; 95% CI 1.09−14.961), who practised hugging (OR 2.39;95% CI 1,23−4.61), who smoked cigarettes (OR 2.99;95% CI 1.42−6.28) and those who used public transport to work (OR 2.91;95% CI 1.46−5.80).

 

We noted that wearing face masks consistently and correctly in public (OR 0.32; 95% CI 0.16−0.63), staying in medium-density suburbs (OR 0.25; 95% CI 0.10−0.67) and consistent use of hand sanitiser (OR 0.48; 95% CI 0.27−0.87) were significant protective factors against contracting SARS-CoV-2 Table 2.

 

We analysed the association between contracting SARS-CoV-2 and being 25 years and above as it was stratified by sex. The crude odds ratio for being age above 25 years and above was within stratum specific odds ratio. Hence, the association between contracting COVID-19 and being 25 years and above was modified by sex (male or female). Females who were 25years and above were 3 times (OR 3.46;95% CI 1.50−7.96) more likely to contract COVID-19 in comparison to men who were 25 years and above (OR 2.39; 95% CI 0.76−7.46)

 

Multivariate analysis

 

We controlled for sex, age. place of residence and employment status as confounding factors. The independent risk factors for contracting SARS-CoV-2 were cigarette smoking (aOR 3.63;95% CI 1.71−7.71) and use of public transport to work (aOR 3.08; 95% CI 1.52−6.25).

 

 

We set out to investigate the risk factors associated with contracting SARS-CoV-2 infection in Norton Town to recommend prevention and control measures. Our investigation revealed that the use of public transport and cigarette smoking were independently associated with contracting SARS-CoV-2. Our study provides evidence that the use of public transport to work was independently associated with contracting SARS-CoV-2 in the community in Norton Town. This finding from our study may be explained by the fact that the majority of cases reported using public transport to work. Public transport has been proven to be an infection transmission area if public health preventive measures are not adhered to [15-17]. Zhen et al. (2020) in a rapid review highlighted that the risk of SARS-CoV-2 transmission on public transport can be improved through ventilation [18]. Our findings are supported by the earlier study by Rozenfeld et al. (2020) who reported that lack of a personal vehicle was associated with contracting SARS-CoV-2 as people could not practise social distance in public transport [19].

 

Cigarette smoking was found to be an independent risk factor for contracting SARS-CoV-2. This could be attributed to the fact that smoking behaviour is characterized by inhalation and by repetitive hand-to-mouth movements, with hands being a source of infection. [20]. Cigarette smoking is also known to cause abnormal inflammatory activation of the bronchial lining increasing the risk of SARS-CoV-2 infection [21]. More so, smokers are more likely to be tested due to the increased prevalence of symptoms consistent with SARS-CoV-2 infection, such as cough and increased sputum production [22]. Cigarette smoking produces exhaled coughing, smoking or sneezing aerosols in the air which will be containing SARS-CoV-2. [23] This finding is consistent with Doung-ngern, et al. (2020) who reported that cigarette smoking was associated with contracting SARS-CoV-2 [14]. Usman et al. (2020) recommended further studies on the association of contracting SARS-CoV-2 and cigarette smoking [24].

 

Limitations

 

Our study had some limitations. During interviews recall and social desirability bias could have been introduced as questions were asked concerning past events. Information bias could have been introduced due to self-reported responses which could not be verified. Bias might have led to overestimation or underestimation of the strength of associations between exposures and the outcome of interest. We tried to minimise recall bias by providing respondents adequate time to think before responding to the questions and the use of a well-structured data collection tool with the same set of questions. Social desirability bias was minimised by giving a brief history of the study so that the participants would not respond in a socially desirable way. We tried to reduce information bias by using a standardised data collection tool for both cases and controls and during interviews questions were posed neutrally.

 

 

Our study provides evidence that cigarette smoking and the use of public transport to work are independently associated with the risk of contracting SARS-CoV-2 in the public and in a town setting. Understanding of factors associated with contracting SARS-CoV-2 will assist in identifying people at risk and instituting public health intervention.

 

Recommendations

 

We recommended continuous and correct public messaging whilst emphasising observing social distancing, correct and consistent hand hygiene and wearing of masks covering the mouth and the nose. Messages should target those who do not adhere to public health preventive measures. Community awareness campaigns on smoking cessation and risks associated with smoking should be carried out.

 

Public health actions taken

 

We intensified messaging on COVID-19 prevention measures and behaviour change in the 13 urban wards in Norton Town using a mobile truck and loud-hailers. We reoriented 65 health care workers on COVID-19 infection prevention and control. We tested all symptomatic patients who presented at Norton hospital for SARS CoV-2. We conducted contact tracing for all confirmed COVID-19 patients. We supervised all funerals and burials of COVID-19 cases. We carried out disinfection of health facilities and homes for deceased COVID-19 cases. The results of the study were presented to Norton hospital Rapid Response Team and Chegutu District Health Executive.

 

 

The authors declare no competing interests.

 

 

MC: conception, design, analysis, and interpretation of data and drafting of the manuscript. PM: conception, design, analysis, interpretation of data and drafting of the manuscript and reviewing of draft manuscript for intellectual content. NTG: conception, design, analysis, interpretation of data and reviewing the draft of the manuscript for intellectual content EG: conception, design, analysis, interpretation of data and reviewing the draft of the manuscript for intellectual content. TPJ: conception, design, analysis, interpretation of data and reviewing several drafts of the manuscript for intellectual content. MO: conception, design, analysis, interpretation of data and reviewing several drafts of the manuscript for intellectual content. MT: conception, design, analysis, interpretation of data and reviewing drafts of the manuscript for intellectual content. The manuscript was read and approved by all authors.

 

 

We would like to acknowledge the following offices for all the assistance that they rendered, Provincial Medical Directorate Mashonaland West Province, District Medical Officer Chegutu District, Medical Officer of Health Norton Town and Health Studies Office, University of Zimbabwe. Many thanks also go to Norton Town residents who participated in the study.

 

 

Table 1: Demographic characteristics of study participants in Norton Town, Zimbabwe, 2021

Table 2: Statistically significant factors associated with contracting SARS-CoV-2, in Norton Town, Zimbabwe, 2021

 

 

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