Background
Scarlet fever, an acute respiratory infectious disease caused by Group A
Streptococcus pyogenes (GAS), most commonly occurs in winter and spring [
1]. GAS usually spreads among the population via respiratory droplets or by direct contact with the mucus, saliva, or skin of an infected person. Some outbreaks of scarlet fever are even found to be food-borne [
2‐
4]. Children from 5 to 15 years of age are vulnerable to scarlet fever [
2,
5]. The signs and symptoms include sore throat, high fever, or skin infection, and the characteristic red rash that feels like sandpaper.
During the nineteenth century, scarlet fever, causing an enormous number of deaths, was a common fatal childhood infectious disease [
6]. With improved nutrition and wide spread use of antibiotics, mortality markedly decreased and rarely occurred in the twentieth century [
7,
8]. Scarlet fever is now a common mild contagious disease that with timely antibiotic therapy has a good prognosis. However, 3% to 5% of untreated cases can result in long-term complications, including rheumatic heart disease, hepatitis, and glomerulonephritis, that consume a large proportion of health care resources [
9‐
11]. As a result of changes in prevalence strain, GAS antibiotic resistance, and the continued unavailability of an effective vaccine [
12‐
17], scarlet fever outbreaks have been reported in many countries and regions, such as Vietnam, Australia, USA, China and England [
2,
14,
17‐
20]. In recent years, the incidence of scarlet fever in China has experienced a sharp increase [
1].
Advances in the geographic information system (GIS) and related technologies have fostered new opportunities to understand diseases from different perspectives. As a useful tool, GIS has been widely applied in controlling infectious diseases [
21‐
23]. However, few studies have focused on the spatiotemporal characteristics of scarlet fever. Gehendra et al. conducted a spatial analysis of scarlet fever in Beijing and detected several high-risk areas. This was essential to take targeted efforts of prevention and control for this disease [
24]. Zheng et al. also explored the clusters of the disease for Gansu Province [
25]. In Jiangsu Province, some researchers described the epidemiology of scarlet fever, but none explored the spatiotemporal patterns [
26‐
29].
In the present study, we concurrently used descriptive analysis and GIS methods to depict the spatial and temporal characteristics of scarlet fever in Jiangsu Province, China. The results might provide some clues for further epidemiological research and help scientists and health authorities to more effectively target their future surveillance and control efforts.
Discussion
According to our study, children aged 3–9 years (appropriate ages for kindergarten or primary school in China) were the main victims of scarlet fever, not only accounting for most of the total cases, but also presenting a much higher incidence rate compared to other age groups. This finding was similar to other studies [
18,
24‐
29]. It might be that low immunity and the concentrated population in kindergarten and primary school could promote the spread of scarlet fever. Interestingly, consistent with other researchers’ results [
24‐
29,
37], we also found that boys were more prone to infection. Boys usually have more physical activities than girls and lack of personal hygiene, which increase the chances of exposure to GAS.
During the study period, a seasonal pattern of scarlet fever was observed in Jiangsu Province. Two distinct epidemic peaks occurred each year. The main peak was from March to July, and the smaller peak from November to the following January. Some researchers have argued that seasonal fluctuation of scarlet fever may be attributed to climate conditions [
38,
39]. Remarkably, both of the peaks happen to occur in the first or second semester of each school year, respectively. Meanwhile, two incidence troughs were observed during summer (August) and winter (February) holidays. Combining this with the prior results indicating that school aged children were the major group with scarlet fever, we can concluded that kindergarten and primary school should be the focus of surveillance and control for this infectious disease.
Notably, spatial heterogeneity of scarlet fever was detected in Jiangsu Province. The results from maps of the incidence and space-time scan analysis suggested that the incidences in southern regions were relatively higher than in northern regions. Nantong city, Suzhou city and Lianyungang city were high endemic regions. Prevention and control efforts should be strengthened in these areas. Although, the three northwest cities of Xuzhou, Suqian and Huai’an were low endemic regions, some spatiotemporal incidence clusters were detected in these cities. This suggested that local high prevalence areas exist within the low endemic regions. Thus, surveillance, prevention, and control in these regions should be given due importance.
The incidence of scarlet fever presented an increasing trend in recent years in Jiangsu Province. This trend is consistent with other regions of China as well as in other countries, and the reasons remain unknown [
1,
12,
14‐
18,
20]. In this case, some conventional measures would be crucial for prevention and control of this disease. Firstly, teachers and parents need to teach school-age children to wash their hands frequently, this is the best way to prevent the disease. They should also avoid sharing personal items, such as eating utensils and towels [
5]. Secondly, schools ought to improve environmental hygiene through disinfection of toys, banisters, and desks, etc. [
17]. In addition, more physical activities should be organized for children to enhance their fitness. Meanwhile, public health authorities should more effectively focus on surveillance, prevention, and control of scarlet fever.
In spite of the above findings, the limitations in our study should be considered. Because some mild cases might use home therapies, and some cases with atypical symptoms may be misdiagnosed, the data reported may underestimate the incidence. Moreover, due to a lack of emm types cases, we could not represent the changes of the circulating strains from 2005 to 2015, this is meaningful to interpretation of the increasing incidence of scarlet fever in Jiangsu Province. Hopefully, a genetic molecular study will be conducted in Jiangsu Province.
Conclusions
In brief, we described the spatiotemporal dynamics of scarlet fever in Jiangsu Province from 2005 to 2015. The prevalence of this disease had an obvious seasonal variation and was relatively highly endemic. School aged children were the major victims, and kindergartens and primary schools should be the focus of surveillance and control for this common disease. The health authorities and policymakers, especially in those endemic areas, should pay close attentions to scarlet fever and make targeted efforts to reduce the incidence rate and maximize the cost-effectiveness of prevention and control programs.