The review provides several important steps in dengue prevention and control. Firstly, future dengue awareness campaigns should be targeted at communities in both endemic and non-endemic areas throughout Malaysia. Secondly, the process of transformation related to their traditional beliefs on health requires continuous processes and integrated cooperation between government (e.g., Health Departments and Department of Occupational Safety and Health of Malaysia), non-government organisation, district office, head of the village (ketua kampung in Malay language), and Village Development and Security Committee (Jawatankuasa Kemajuan dan Keselamatan Kampung in Malay language). Thirdly, active participation and effective communication should be fostered when conducting regular voluntary communal works, aiming to motivate and strengthen a healthy lifestyle, such as the integration of appropriate dengue prevention practices. Besides, in this sort of setting, conventional education campaign to increase dengue awareness is useful, but the programme materials need to be evaluated on a routine basis, including health messages content, as well as training of personnel to deliver educational messages. In fact, a study in Cambodia ^[32][99] revealed that the content of the materials in health pamphlets was not always practical or effective in preventing mosquito bites, leading to difficulty in knowledge translation to the communities. In addition, when designing health pamphlets regarding dengue, the level of literacy and cognitive understanding of the concerned population should be considered and incorporated in the final product ^[33][100]. Lastly, ingrained and negative habits are difficult to discourage with plain knowledge sharing. Perhaps more personal and practical approaches in the health education programmes are required to stimulate behavioural change, including co-operation with faith-based organisations, particularly in rural areas, in Malaysia.

3. Treatment-Seeking Behaviour

Despite the importance of immediate treatment-seeking behaviour upon dengue infection, only a few studies have been conducted in Malaysia. Similar patterns of treatment-seeking behaviour have been demonstrated in Myanmar ^[34][101] and Venezuela ^[35][102], reflecting a lack of awareness of the need for immediate medical attention for dengue. This situation could be caused by several factors, including: (i) misconception that dengue is easily curable without progression to further complications, and this intention is worrying; (ii) poor transportation amongst rural populations in certain states of Malaysia, such as Sabah and Sarawak; (iii) poor healthcare services, such as poor ambulance response time in case of emergency, lack of facilities, and low skills of health care providers, that lead to lack of confidence among community residents ^[36][37][38][103,104,105] could partly explain the reason for a delay in treatment-seeking behaviour among Malaysian population; and (iv) dependency to symptom-relief-based supporting therapy, especially over-the-counter medication like paracetamol ^[39][106].

The findings in this review suggested several recommendations to improve the dengue treatment-seeking behaviour. Firstly, comprehensive information on dengue should be included in health education at all levels in the community, including school-aged children ^[40][61], regarding the critical of seeking immediate treatment through raising awareness on the importance of early attendance to health centres. This recommendation is vital to populations at higher risk of dengue infection, such as “sociodemographic-deprived” and history of dengue hospitalisation, due to the fact that they are prone to a higher risk of clinical complications, such as severe dengue, and even death. Besides, home-based treatment, such as the use of paracetamol or traditional medicines, needs to be assessed for efficacy and safety as it is widely perceived and experienced as efficacious for treating dengue in Malaysia, especially among rural populations ^[41][107]. This is because a multi-centre randomised controlled trial demonstrated that the use of standard-dose paracetamol in dengue infection increased the incidence of transaminase elevation in the liver and clinical complications, such as gastric haemorrhage and acute kidney injury ^[42][108].

4. Acceptance of Diagnostic and Preventive Treatment

Based on a study by Yeo et al. (2018) (40), the rate of dengue vaccine acceptance in a subset of the Malaysia population was lower than a similar study in Bandung, Indonesia (88.4% vs. 95%) ^[43][109]. This information on dengue acceptance is important as one of the criteria that World Health Organisation (WHO) recommends for vaccine implementation in a population ^[44][110]. However, further study is warranted to assess the strength of the country’s current immunisation system and the characteristics of the vaccine itself.

Overall, this review showed that the level of acceptance towards diagnostic or preventive treatment, such as dengue vaccine, bacteria (Wolbachia) as a vector for dengue control, and self-test diagnostic kit for dengue, was significantly associated with the level of dengue knowledge. Theoretically, people with higher dengue knowledge are more aware of any information, including the benefits of vaccination, limitations of treatment, and the importance of early dengue detection, such as using a home self-use kit. Similar association has also been demonstrated in other infectious diseases, such as the human papillomavirus vaccine ^[45][111] and influenza ^[46][112].

Additionally, the acceptance of a hypothetical dengue vaccine was significantly associated with their attitude towards vaccination practice in Malaysia, suggesting a need to improve their attitude as it has a more discernible effect on increasing vaccine acceptance. Similar findings have been reported in the Indonesian population ^[43][109]. Furthermore, a study in Indonesia ^[47][113] demonstrated the importance of parental acceptance on the school children’s vaccination programme as reflected in national coverage of the Expanded Programme of Immunisation (EPI) vaccination (>90% amongst infants and school children). It has been reported that other populations also adopted a similar attitude towards vaccination against other infectious diseases, such as human papillomavirus ^[48][114], influenza A virus subtype H1N1 ^[49][115], rubella, and measles ^[50][116]. Furthermore, the acceptability of the dengue vaccine is also associated with trust in public health institutions, vaccination programmes, and health institutions, making them accept the vaccine rooted in the controversial vaccine experience as shown by the Philippines population ^[51][117].

Given the aforementioned situation, it is therefore deemed essential to increase public health trust by any means via incorporation of community participation, health promotion programme, and informal social networks in disseminating public health messages. Interesting findings in a unique Malaysia multi-ethnicity country showed the importance of ethnicity in the acceptance of a hypothetical dengue vaccine ^[52][41]. It is possible that the differences are not due to ethnicity per se but due to other sociodemographic characteristics, such as age, gender, level of education, or occupation. The disparities across the three main ethnic groups in the use of dengue home test kits if available would be interesting to investigate further.

5. CAM as Dengue Treatment

It was reported that a high number of dengue patients in the central region of Peninsular Malaysia depend on complementary medicine (85.3%), which is similar to the East Coast of Peninsular Malaysia (84.6%) ^[41][107]. Interestingly, the reported prevalence rate was found lower in an earlier study involving all states in Malaysia (69.4%) ^[53][118], Japan (76%) ^[54][119], South Korea (ranged 29% to 83%) ^[55][120], and Singapore (76%) ^[56][121]. The variations in the prevalence may be due to one or multiple factors, including methodological criteria of assessment (e.g., age of the population examined, locality of the studied region and CAM definition) and the purpose of using CAM for health maintenance rather than for treating illness.

According to the review findings, the use of CAM, such as papaya leaf extract (Carica papaya), was increased amongst dengue patients, particularly among rural populations due to economic and geographical constraints ^[57][122]. Similar findings have been shown in other populations in Indonesia ^[58][123], the Philippines ^[59][124], and India ^[60][125]. Clinical studies have reported the beneficial effects of C. papaya on dengue patients by improving their platelet counts, reducing inflammatory reactions ^[61][126] and maintaining the stability of the haematocrit level ^[58][123]. Arguably, this finding did not correlate with life-threatening complications of dengue infection, such as plasma leakage and shock syndrome ^[62][127]. Therefore, the use of C. papaya is limited as acute and temporary dengue management for rural populations while waiting for transportation to receive hospital management. Similarly, the use of isotonic drink did not reduce dengue severity other than giving supportive effects helping dengue patients to regain energy. In view of diabetes, it may endanger the life of a diabetic patient infected with dengue due to its high sugar content ^[63][128] if over-consumed.

With the advancement of molecular techniques, a more comprehensive study on the association of different genes in determining other roles of C. papaya is warranted in order to justify the value of conducting a dengue awareness campaign on CAM in Malaysia. Alternatively, leaves extract of C. papaya has been demonstrated to have larvicidal activity against mosquito Aedes, the primary dengue vector for dengue infection, suggesting an ideal approach for vector control programme ^[64][129]. Although reports have concluded that the administration of C. papaya is safe ^[65][130], further study is required to elucidate its mechanistic action in providing alternative or adjuvant therapy to dengue patients.

Lastly, the analysis in this review also discovered that an association between the use of CAM and higher level of education, which is consistent with another local study among dengue patients in the northeast region of Peninsular Malaysia ^[41][107]. This finding may be due to the fact that they are more aware of dengue complications, making them search for health supplements to complement the treatment received in the hospital. Similar findings were also reported in other populations ^[55][120].

6. HBM Construct Association with Dengue Prevention Practices

HBM constructs can be utilised to predict people’s behaviour or why people take action to control or prevent a specific illness or disease. They can guide the plan of dengue interventions and the development of an effective awareness or targeted educational programme in Malaysia. However, only six out of 57 studies in this review considered HBM constructs and not all of them correlate to attitude and practices.

Multiple studies have indicated that the practice of protective behaviours is more dependent on the beliefs based on HBM constructs. Although only one study correlated the HBM constructs with prevention practices, the perceived barriers and perceived susceptibility constructs of the HBM were significantly related to prevention practices ^[66][62]. People with lower perceived barriers were significantly related to higher dengue prevention practices ^[66][62]. To perform dengue prevention effectively, it is imperative to eliminate barriers hindering actions against dengue. For instance, a qualitative study conducted amongst the Indonesian population ^[67][131] demonstrated the importance of clarifying appropriate action and promoting positive effects on performing dengue vector control to reduce persistent dengue transmission. Similar to cancers, another study among female students in Botswana, Southern Africa, showed that misconception could act as a barrier to breast cancer screening ^[68][132], indicating the importance of identifying and reducing perceived barriers through interventional programmes to correct health misinformation.

In addition, people with lower perceived susceptibility to dengue were less possible to carry out dengue prevention practices, most probably due to Orang Asli are either not aware of the serious consequences of dengue fever or never experienced themselves. Previous studies have revealed that if action is expected to occur, the individual perceives the susceptibility of having the illness ^[69][133]. A recent study in the dengue-endemic city Karachi, Pakistan ^[70][134] showed that perceived threat was significantly associated (p = 0.000–0.007) with acquiring information on dengue knowledge among populations as compared to low intensity to acquire knowledge on dengue in a non-endemic area of dengue in Malaysia ^[71][33]. This finding is important because it is a prerequisite for population stratification based on risk levels, personalise risk based on a person’s characteristics or behaviour, making perceived susceptibility more consistent with individuals’ actual risk or specify consequences of risks and conditions.

In this review, only one study related HBM concepts with attitude, and they found that the highest satisfactory attitude was in the perceived benefit concept ^[72][26]. Hence, this study highlighted that health education, campaigns and knowledge of dengue fever were highly required and essential in order to improve preventive practices among communities, particularly Orang Asli. It was further suggested that health messages and education awareness campaigns should be prepared in accordance with HBM constructs.

Based on the above, it is noted that HBM plays an important role and should be used as the predominant theory-driven intervention strategies to reduce dengue. However, in interpreting the relationship of HBM constructs as a conceptual guiding framework for health behaviour intervention, caution must be exercised when drawing a conclusion as HBM has some limitations. One example is that HBM does not account for environmental factors that may prevent an individual from practising the desired preventive practices, including poor infrastructure, bad sanitation, and inadequate water supply experienced by community residents. Thus, it is essential for the government and private sectors to work co-operatively providing facilities to remove the barriers in conjunction with behavioural change interventions of the community for sustainable dengue prevention and control.

7. Awareness and Utilization of Clinical Practice Guidelines (CPG)

The Ministry of Health in Malaysia has adapted the CPG prepared by the WHO for managing dengue, with evidence of good awareness by clinicians. Despite quantitative survey evidence on a high level of dengue awareness regarding CPG amongst medical doctors in Malaysia ^[73][53], the study showed differences amongst medical practitioners in public and private health facilities. It could be explained that medical doctors in public health facilities are younger, thus they are more likely to look for guidance in managing their patients. Comparatively, those working as private health practitioners tend to undermine their well-experienced clinical practice in managing their patients.

Nonetheless, several studies in other countries ^[74][75][76][135,136,137] have demonstrated that the recommendations stated in the CPG are impractical in some clinical settings, including limitations in consulting time, lack of resources, lack of attention to the logistics of implementation, or lack of detail on particular patient groups. Due to this, the adaptation of ‘local’ guidelines in public health facilities with highly dengue admission rate has been reported, which generally advocated fixed regimes of fluid management with limited resources ^[77][138].

Although public facilities continuously conduct training to their staff regarding CPG to enhance their awareness and implementation, the use of standard CPG could result in a problematic situation in a patient requiring more tailored fluid regimes. Therefore, the final decision on the implementation of guidelines in routine patient management should be evaluated thoroughly to maximise the benefits to the patients. Importantly, providing guidelines in clinical settings should be in line with the emerging model of translational science in healthcare, which integrates translational research and effectiveness a novel and timely evidence-based revision ^[78][139] for maximal benefit of the patients.

8. Sources of Information on Dengue

In this review, the analysis showed that most Malaysians obtained information regarding dengue from mass media, such as television, radio, and newspaper, suggesting that this platform is important in disseminating dengue-related information to raise better awareness. Additionally, more audiences are increasingly engaging with online social media, including Facebook, Instagram, Twitter and other smartphone dating applications. The obtained dengue-related information could be utilised for health promotion and would be a promising method due to relatively inexpensive, convenient accessibility and a fast approach. However, astoundingly, over 72% of Malaysian national ground territory seemingly has near-zero telecommunication coverage, with a major void even in the central Malaysian peninsula ^[79][140], that could create information barriers. Moreover, one should be aware of the fact that not all the information accessible through social media is credible.

Recent studies have suggested that dengue outbreaks are increasing in rural settings of Sabah due to urbanisation and deforestation ^[25][92], thus increasing dengue awareness and preventive practices are urgently needed in this area. An effective method of delivering dengue information in rural areas would be a community-based health education delivered by nearby health center outreach activities and health campaigns as demonstrated amongst rural population in Cambodia ^[32][99]. However, the outcome from the previous study recommended that a more persuasive approach, such as modelling of performing the desired behaviours or relating their personal sufferings due to their attitude and practices, should be incorporated in health education as it could form better confidence amongst respondents ^[80][141]. Additionally, health education could be conducted by healthcare providers to provide dengue-related speeches in formal or non-formal religious lecture sessions in religious centres, such as mosques, churches, or temples, as it has been shown to provide a similar opportunity for increasing dengue awareness in Indonesia ^[14][83].

Surprisingly, this review showed that healthcare providers demonstrated a lower function as a source of attaining dengue-related information amongst respondents. This issue merits a further examination, as they are considered as the frontliners that highlight the importance of prompt treatment of dengue patients. This finding is opposed to a study in Aceh, Indonesia, that healthcare providers had been cited as a major source of information on dengue ^[14][83]. The contradicting finding could be due to patients perceived trustworthiness and acceptance of healthcare services as reported in Uganda, Africa ^[81][142]. Plausibly, the Communications for Behavioural Changes (COMBI) programme on dengue prevention implemented by Health Departments and developers at construction sites to promote dengue awareness and prevention failed to achieve desired behavioural impact among community ^[82][143], which may be due to lacking respectful and supportive patient-provider interactions.

9. Lack of Evidence in the Questionnaire’s Reliability and Validity

Validity and reliability are very important to measure the accuracy and consistency of research tools, particularly questionnaires. However, their measure is not regularly conducted among healthcare researchers in developing countries. The reliability of a questionnaire is usually measured using a pilot test. Moreover, the reliability could be assessed in three major forms, including test-retest reliability, alternate-form reliability and internal consistency reliability. It is important to take note that some studies have mentioned that a pilot study has been carried ^{[83][84][73][85][86]}[36,38,53,57,67]; however, the findings of the pilot study were not reported.

In regard to validity, many subtypes of validity are available, such as face, content, criterion, and construct validity ^[87][144]. In fact, all questionnaire studies should report at least the minimum internal consistency coefficient of Cronbach’s alpha values ^[12][21]. For an exploratory or pilot study, it is suggested that reliability should be equal to or above 0.60. In this review, most articles neither report the findings of the pilot study nor of the questionnaire pre-test. Although reliability is important for the study, it is not sufficient unless the validity of the study is provided ^[12][21]. In other words, it is crucial for a questionnaire to include a validity index ^[88][145]. Thus, the underlying construct of the items in a newly developed questionnaire should be analysed by factor analysis ^[89][146] to predict the discriminant and convergent validity. However, only one study was found in this review had carried out the factor analysis ^[90][75]. The reliability, content and construct validity of the questionnaire should be carefully examined. It is crucial to harmonise and validate the content of all structured questionnaires, with the aim of reducing the heterogeneity of findings and obtaining quality results based on the questionnaire used for data collection ^[56][91][121,147].