The recent COVID-19 outbreak has stimulated a public-driven movement for prevention and governments worldwide have made many attempts to control the situation resulting from emergence of COVID-19. This included the implementation of NPIs at personal and at country levels. Since other viral respiratory infections shared same transmission dynamincs with COVID-19 where these viruses spread through close contact, aerosols and/or droplets, therefore, implemented measures could not only curtail the spread of SARS-CoV-2, but might also impact the occurence of ILI and reduce the transmission of other viral respiratory infections.
Study main findings
The current study argue that participants who exhibited high level of adherence to COVID-19 personal protective measures were more likely of being free of influenza-like illnesses during the flu season compared to those who did not adhere to the measures. This strongly suggested that the protective measures taken against the spread of SARS-CoV-2 have also interrupted the spread of ILI. Our results were in line with the findings of previous studies that emphasized the potential of community-level strategies used to halt the spread of SARS-CoV-2 in lowering influenza transmission was revealed in several studies (16, 26, 27). Furthermore, a longitudinal study conducted among international students found a two-fold increased risk of ILI among students who did not implement all the personal protective measures compared with those who adhered to the measures (28).Of note, a similar impact of implemented protective measures was detected in European countries such as Austria, Belgium, Italy, Germany, Spain and the Netherlands (29).
Our finding revealed the potential of wearing facemasks on a regular basis (frequently or always) in decreasing the occurrence of ILI among participants(aOR=0.452) in comparison with other individuals who didn’t adhere to this protective measure. Based on the literature, several studies aimed to evaluate the effectiveness of facemask use in preventing pandemic influenza infection (30-38). Some of the overmentioned studies reported similar results as our study such as the findings of cross-sectional survey conducted by kim et al. (34) which revealed a significant protective effect of continuous mask use in children, relative to non-users (OR = 0.51; 95% CI 0.30-0.88), but a non-significant risk increase in irregular users relative to non-users (OR = 1.02; 95% CI 0.83–1.25). A cohort study conducted by Kuster et al. showed also that for each 10% increase in adherence to facial protection, there is a decrease (OR = 0.92) of that the risk of being infected by influenza viruses among healthcare workers (37). Similarly, Suess et al. found in his cluster randomized control trial a significantly protective effect of facemask use (OR = 0.28) (35). However, some studies (30, 33, 38) found a non-significant protective effect of facemask in preventing influenza infection.
In terms of hand hygiene, washing hands regularly and continually was found associated with lower risk of suffering from ILI symptoms. Given the high compliance rate among study participants (95.5%) reporting always or frequently their hands, the results of this study provide a reliable estimate of the impact of hand hygiene in preventing influenza-like illnesses in the context of a pandemic. Our findings were consistent with the results of several studies evaluating the effectiveness of hand hygiene in preventing influenza infection (31, 32, 35-37, 39). A study conducted by Aiello et al. reported that hand hygiene decreases respiratory infections by 16%–21% (40). Azor-Martinez et al. reported that the school absenteeism associated with pandemic influenza declined in schools that implemented hand sanitizer intervention (39). Swess et al found that the combination of hand hygiene with facemask use(OR = 0.26) were able to decrease the risk of secondary influenza infection (35). However, inconsistent findings in terms of protective effect of hand hygiene were reported by Kim et al who found a non-significant protective effect of subjectively reported “frequent” hand-washing, with OR = 0.99 (95% CI 0.96–1.02). Of note, the protective effect of this intervention was more pronounced in studies where frequency was defined objectively based on a minimum number of times individuals washed their hands daily.
Our study disclosed the potential of the adherence to physical distancing and avoidance of crowded places in decreasing the likelihood of experiencing symptoms of influenza-like illnesses when compared with those who did not adhere at all to these measures. Prem et al. reported the benefits of limiting social mixing (41). However, a previous study conducted among international students did not find any significant association between cases of influenza-like illnesses and avoiding crowded places (28). Of note, the evidence regarding the benefit of avoiding crowded places in preventing respiratory virus infection in individuals remains scarce.
Additionally, our study found a significant association between surface disinfection and reported cases of influenza-like illnesses among Lebanese adults. Our results were in accordance with a previous study that revealed the potential of surface disinfection effectively decreases secondary COVID-19 transmission in households (42).
In terms of cough etiquette which was found associated with lower likelihood of suffering from ILI, no studies were found that evaluated the effectiveness of respiratory etiquette on ILI transmission. However, a study appraising the efficiency of cough etiquette in blocking aerosol particles, found that cough etiquette did not block the release or dispersion of aerosol droplets, particularly those smaller than one micron in size (43).Of note, influenza particles are extremely small (0.08–0.12 μm in diameter) (44), and could easily be transmitted in small droplets expelled during sneezing or coughing.
It is noteworthy that influenza vaccine intake that was found decreasing the likelihood of occurrence of ILI among participants, it is important to mention that the recommendations for vaccination against influenza during this influenza season did not change compared with previous seasons. In Lebanon, the influenza vaccines are normally administered from 1 October each year. However, in the 2020/2021 season, the influenza vaccination was delayed a little bit due to the delay in purchasing the influenza vaccines. However, it is unlikely that the vaccination could have resulted in the sudden sharp decline seen in the occurrence of ILI, since the latest could result from other respiratory viruses. Of note, the low circulation of influenza viruses for one or two seasons shown in several countries could minimize the exposure of young children to these viruses and enlarge the group of children who will be susceptible in the following influenza season.
In summary, the adherence to each of the six personal protective measures recommended by the WHO reduced cases of ILI among Lebanese adults participating in this study. In addition, a synergic implementation of all of the overmentioned personal protective measures offered higher protection to individuals compared with single measures.
Strenghths of the study:
To the best of our knowledge, the present study is the first in lebanon to successfully explore the association between practice of personal protection measures and the risk of influenza-like illnesses in the community during the 2020–2021 flu season. Given the current economic crisis, the fear of COVID-19, the overstrain of healthcare system and the recommendation issued by the government to minimize face to face interaction, Lebanese adults with ILI could hesitate to visit healthcare services and often delay accessing healthcare. Thus, our findings provide a snapshot of the reported cases of ILI among the community where healthcare avoidance may be an important confounder affecting the findings of healthcare-based acute respiratory infection surveillance system. Therefore, our participants could represent a category that may not be captured in hospital visits.
Several limitations should be acknowledged in this study. First, the cross-sectional design of our study preclude the ability to make a causal inference and its retrospective nature presents a risk of reporting biases, which could over-estimate the true effectiveness of the personal protective measures in preventing ILI infection, as ILI cases and free ILI cases may misjudge their adoption of these measures in order to justify their infection status. For example, participants gave a self-reported history of ILI which could be subject to recall bias. In addition, respondents gave their self-evaluation using subjective terms to define frequency of of their implementation of personal protective measures against COVID-19 such as “rarely”, “occasionally” or “sometimes”, which may be affected by social desirability and could led to a possible overestimation of their implementation. To resolve any potential social desirability bias, an anonymous online survey was used and participants were assured of the confidentiality of their responses in the introductory part of the survey.The study evaluated only the preventive effects of 6 personal protective measures; other measures may have contributed to suppressing transmission of respiratory infections such as lockdown, mass gathering cancellation and school closure. Furthermore, the convenience sampling technique used in our study, limit the generalizability of our findings. However, a large sample was used to reduce the sampling error and to increase the study power. Lastly, a knowledge gap related to the appropriate “threshold” for adequate personal protective measure scale, exist. It is likely that this will vary depending on individual factors such as exposure, susceptibility and risk of adverse outcomes.
Implications of the study and future directions
Our findings suggest that the adherence to these measures can ameliorate the impact from other respiratory pathogens, reducing the strain on healthcare infrastructure. Such findings may be particularly helpful for developing prevention strategies in settings where respiratory infections are very harmful, such as congregate settings and for the elderly and immunosuppressed. Even once the pandemic resolves, practices implemented to reduce COVID-19 transmission may be advisable for vulnerable individuals (elderly, immunocompromised…) particularly in high-risk settings(nursing homes, facilities, entertainment venues), or during travel, especially during the winter months at the annual peak of most respiratory viral infections. As society reels from the financial, societal, and health costs of severe COVID-19 response measures globally, interdisciplinary researchers and policy-makers globally were invited to investigate and facilitate the precise level of prevention for future epidemics. An important implication of this study was the need to perform such maneuvers frequently to curtail the transmission of COVID-19 and reduce the overall burden of communicable diseases, therefore the general public is urged to actively apply these preventative measures. Risk communication strategies to enhance public’ knowledge in this area are crucial to clarify locations and situations where viral contact is likely, and to emphasize the value of engaging in such protective behaviours.