Symptom cluster patterns
As of Nov. 20, 2020, information of 1067 cases were collected. Based on the results of text clustering, symptoms were summarized into the following 4 groups: Group 1: No-obvious symptoms, refers to those with no obvious symptoms but positive nucleic acid test; Group 2: Mainly fever and/or dry cough, refers to those with fever as the main symptoms, or accompanied by dry cough; Group 3: Mainly upper respiratory tract infection symptoms, refers to those mainly with expectoration and upper respiratory tract infection symptoms, such as, pharyngodynia, stuffy nose and runny nose, or accompanied by fever; Group 4: Mainly cardiopulmonary, systemic and/or gastrointestinal symptoms, refers to those whose main symptoms were cardiopulmonary symptoms such as shortness of breath, dyspnea, chest tightness, chest pain, and/or systemic symptoms such as fatigue, chills and muscle aches, and/or symptoms of the gastrointestinal system such as nausea, vomiting and diarrhea, sometimes accompanied by fever and upper respiratory tract symptoms.
The results showed that more than half (50.7%) of the infected persons did not show obvious symptoms at the first visit, i.e. in the group 1. For the three groups with obvious symptoms, the proportions were 12.6%, 10.0% and 26.8%, respectively. Group 4, that were cardiopulmonary, systemic and/or gastrointestinal symptoms had higher proportion.
In order to profile the symptoms composition under each group, bar charts were applied to visualize the particular symptoms under each group (Fig. 2). It could be seen that there were overlaps and interactions of symptoms under a same group. In symptom group 1, all with no-obvious symptoms (541 cases,100%); In symptom group 2, the most frequent symptom combinations were fever only (64 cases, 47.8%) , followed by dry cough only(42 cases, 31.3%); In symptom group 3, the most frequent symptom combinations was expectoration only(21 cases, 19.8%), followed by fever complicated with expectoration (10 cases, 9.4%); In symptom group 4, the most frequent symptom combinations was fatigue complicated with fever (12 cases, 4.2%), the incidence of headache complicated with fever was also high (11 cases, 3.8%).
Fig. 3 shows a word cloud based on the frequency of individual symptoms under each group. The larger the font, the higher the frequency. It could be seen that fever and dry cough were the two most frequent symptoms in general, with frequencies of 64.4% and 38.8%, respectively, followed by expectoration (12.0%) and fatigue (11.4%). Fever (68.7%) and dry cough(52.24%) were the dominant symptoms in group 2; Expectoration(59.4%) was the dominant symptom in group 3; And fatigue(42.7%) and headache(26.2%) were the dominant symptoms in symptom group 4. Under each symptom group, symptoms showed some clustering around the dominant symptoms.
Population distribution in different symptom groups
Of the 1067 cases, 699(65.51%) were males and 368(34.49%) were females. The median age was 35 years. Population characteristics of the above symptom groups were summarized in Table 1. According to Sijia Tian et al.[17], we divide the infected into four groups aged 0-12,13-44,45-64, ≥65 years. The majority of infected persons were in 13-44(613 cases, 57.45%) and 45-64(344 cases, 32.23%) years age groups. For comorbidities, the prevalence of hypertension was 6.84%, while were 2.44%, 1.88% and 2.06% of diabetes, lung disease and cardiovascular disease, respectively. In addition, 41.24% of the infected patients were imported cases and 26.43% were infected with family cluster.
Factors associated with different symptom groups
The results of multinomial logistic regression (Table 2) showed that age, comorbidities and epidemiological characteristics were all independent influencing factors of the presence of symptom group 4, namely symptoms such as cardiopulmonary, systemic and/or gastrointestinal symptoms. Compared with the 0-12 years age group, the odds of symptoms of group 4 increased in both the 13-44 years and 45-64 years age groups (OR = 4.08, P = 0.032; OR = 5.91, P = 0.007). In addition, in order to further analyze whether there is any difference in the odds of the three obvious symptom groups in age groups compared with ≥65 years group, an analysis was carried out with the group of ≥65 years as the reference. It is noteworthy that people aged 45-64 years were more likely to develop symptoms of group 4 (OR = 2.66, P=0.015) when compared with the ≥65 years group.
No significant differences in the odds of the above three obvious symptom groups were detected between the sexes. For the comorbidities, the odds of showing symptom group 2 was no significant differences between patients with and without diabetes (P = 0.111), but in those with diabetes, the odds of group 3 and group 4 had significantly escalated (OR = 29.43, P= 0.004; OR = 41.72, P = 0.001), indicating diabetes a strong risk factor for upper respiratory tract symptoms, cardiopulmonary, systemic and/or gastrointestinal symptoms. In addition, the results showed that there was no significant difference in the odds of all the three obvious symptom groups between patients with or without hypertension, lung disease or cardiovascular disease.
Besides, the results showed that, the incidences of all the 3 obvious symptom groups were lower in the imported cases and the patients infected with cluster than in the indigenous cases and non-clustered cases, respectively (OR< 1, P < 0.05).
Time intervals between symptoms onset and the first visit
In all the symptomatic cases, the median time interval between symptoms onset and the first visit was 1 day, and the interquartile range was (0,3) days. 47.5% of symptomatic patients visited a medical institution on the day of symptoms onset, 15.4% one day after onset and 11.4% two days after onset, and 25.7% sought medical treatment three days or more after onset. Fig. 4 is a graph displaying the proportions of cases with the three groups of obvious symptoms as the time intervals lengthened. It could be seen that the proportion of symptom group 2 was decreasing as the time interval lengthened, while in symptom group 4, it was increasing over longer time intervals, and in symptom group 3, its proportion peak was in the middle.
Noting that the results showed people aged 45-64 years were more likely to show more severe symptoms than people aged 65 or older, in order to explore whether this was affected by the progression of symptoms, we analyzed the time intervals between symptom onset and visit in different age groups. The results showed that the median time intervals of 0-12, 13-44, 45-64 years groups were all 1 day, while it was 0 day of ≥65 years group (Fig. 5). And the ranges were longer in 13-44 years age group and 45-64 years age group, with ranges of (0,14) days and (0,15) days respectively, while which in 0-12 years age group and ≥65 years age group were (0,7) days and (0,8) days respectively. Patients aged 12-64 years had longer time intervals.