Since morbidity, mortality, and healthcare costs are impacted by HAI, this study aimed to analyze its prevalence at The First Affiliated Hospital, Sun Yat-sen University over a four-year period. The results indicated that the annual prevalence of HAI significantly decreased from 2.39% in 2018 to 1.41% in 2021. Interestingly, the prevalence of HAI in this study was also less than that reported in most previous studies, both domestic and foreign [2, 5, 6].
Not only the prevalence rates of HAI were greater in ICU patients who were vulnerable due to their underlying comorbidities and the presence of invasive catheters and devices, affecting nearly 30% of patients and similar to previous studies [17, 18], but HAI also occurred in nearly 30% of surgical patients in our hospital. Thus, strengthening HAI surveillance and implementing control measures in both the ICU and the surgical department are important aspects of HAI reduction.
In this study, respiratory tract infection was found to be the most common type of HAI, with an average of 44.47% over four years, a prevalence which was significantly less than that in a tertiary general hospital in Beijing (64.7%) . While the reduction and control of the prevalence of respiratory tract infection should be a priority within China to reduce the prevalence of HAI, the prevalence of ventilator-associated pneumonia remained almost constant (9.70 per 1000 patient days in 2018–2021) in our study and was obviously greater than that found in hospitals in the USA (3.20 per 1000 patient days in 2015) .
The use of antibiotics reported in the current study revealed a prevalence of 37.6%, which was less than that in the USA (51.9%)  but greater than that in the European Union (30.5%) . Moreover, bloodstream infection is defined by the presence of microorganisms in the blood, which might result in underreporting in many hospitals due to the high use of antibiotics that results in some blood cultures giving false-negative results. In this regard, bloodstream infection accounted for 11.59% of HAIs in this study, which was only less than the prevalence of respiratory tract infection. A systematic review of the prevalence of HAI in Mainland China has revealed, however, that the average prevalence of bloodstream infection in general hospitals in China from 2006 to 2016 was 2.65% , which is much less than that found in the current study. This finding might be due to the encouragement of blood culture to increase the detection rate of microbiological testing.
Furthermore, this study documented a much higher proportion of nondevice-associated urinary tract infections (69%) than catheter-associated urinary tract infections (0.53%), thus revealing the importance of infection control for nondevice-associated infections. In contrast, the most common type of HAI in a study in Germany was urinary tract infection (21.6%), which was associated with catheter use in more than 60% of cases . In Germany, approximately 15–25% of all inpatients receive catheterization at least once during their hospital stay, but catheter-associated bacteriuria is usually asymptomatic, and less than 5% of cases result in bacteremia requiring treatment .
Given the potential impact of the COVID-19 pandemic on HAI prevention and surveillance, this study analyzed and identified potential changes in the prevalence and distribution of HAI between 2018–2019 and 2020–2021. Inconsistent with previous studies in US hospitals , a widespread decrease in HAI prevalence, especially that related to respiratory tract infection, has been observed in this study’s hospital since the outbreak of COVID-19 at the end of 2019.
Since the outbreak of COVID-19, most Chinese people have developed the habit of wearing face masks in public areas to prevent the spread of respiratory pathogens. Leung et al. have reported that surgical face mask use can significantly reduce the transmission of human coronaviruses, influenza viruses, and rhinoviruses in respiratory droplets or aerosols from symptomatic individuals [23, 24]. During the COVID-19 pandemic, the increased focus on hand hygiene, the use of personal protective equipment, environmental cleaning, and patient isolation as well as the addition of bioaerosol treatment and COVID-19 mitigation measures significantly reduced airborne ultrafine particles and altered the bioburden of hospital environments, which may have resulted in the reduction of HAI prevalence in medical institutions [13, 22]. Specifically, the HAI prevalence steadily decreased from 2018 to 2021, ranging from 2.39% in 2018 to 1.41% in 2021. To prevent the spread of disease, our hospital implemented a series of strict management measures during the COVID-19 pandemic. First, all people entering hospital areas must wear masks and are not allowed to take them off. Second, family members of patients are forbidden to visit patients in the inpatient ward, and strict management measures have been implemented for patients’ caretakers; for example, non-necessary caretakers are not allowed to stay in the ward, only one fixed caretaker is allowed to stay in the ward if necessary, and the caretakers are not allowed to walk around the ward at will. Third, additional sickbeds in inpatient wards are prohibited, and the distance between sickbeds must be strictly maintained, including 0.8 m for general wards and 1.0 m for ICU wards. Fourth, the environmental surface of the general wards is disinfected with 500 mg/L chlorine-containing disinfectant at least twice a day. Also, surface disinfection of inpatient elevators occurs once every 2 h, and air disinfection of outpatient elevators occurs twice a day. Finally, staff with a fever, respiratory tract infection, or other symptoms are not allowed to come to the hospital to work, until these symptoms disappear.
Interestingly, not only have we found that the prevalence of HAI peaked in the winter, from December to February of the following year, but our meteorological data also showed that these three months were the months with the lowest outdoor temperature in Guangzhou, China. In our study, the HAI prevalence was negatively correlated with the outdoor temperature. Similar to previous investigations, seasonal variation would affect the prevalence of respiratory tract infection on account of the cold weather, which is associated with the increased occurrence of respiratory tract infection [25, 26].
Although we found that the outdoor temperature was an important factor of the regional and seasonal factors that led to the difference in the prevalence of HAI, it was not the only factor. For example, whether the economic difference is also one of the reasons for the regional differences in HAI was not addressed. Nevertheless, there are huge discrepancies in socioeconomic conditions and the gross domestic product between different provinces and regions in China ; therefore, it is difficult to interpret whether the different HAI rates across regions may be related to social or economic determinants.
Consistent with respiratory tract infection, the prevalence of gastrointestinal infection, intra-abdominal infection, surgical site infection, deep surgical site infection, and intracranial infection was greater in the winter. Nevertheless, the prevalence of urinary tract infection was lower during the winter months. Gastrointestinal infection has been associated with seasonal variation because the viruses are introduced into the hospital by infected patients on admission during community outbreaks during the winter . Meanwhile, previous studies have revealed that urinary tract infections have a strong pattern of seasonality, with peaks in the summer and troughs in the winter . The morbidity of urinary tract infections may increase with rising temperatures. Also, dehydration and the corresponding lower urine output caused by warmer weather may be the reason for the seasonality of urinary tract infections .
Several limitations in this study should be mentioned. First, this study was performed in a single-center; therefore, our findings cannot be generalized to all hospitals in different regions of China. Second, the details of infection were more clearly recorded in patients with longer hospital stays compared with those with a shorter hospital stay, leading to data regarding temporary infections to be neglected. Lastly, due to the lack of relevant socioeconomic data, the influence of socioeconomic factors on HAI was not taken into account in our study.