Abstract
Vibrio vulnificus sepsis is acute septicemia caused by V. vulnificus and it is a class 3 infectious disease designated under the Infectious Disease Control and Prevention Act. The mean number of cases over the years 2018 to 2022, in the Republic of Korea, was 51.4, with a fatality rate of 38.6%. In 2023, there were 69 patients with V. vulnificus sepsis (patients or probable patients) and 27 deaths, with a fatality rate of 39.1%. In 2023, the number of patients increased approximately 1.3 times compared to the mean of the previous five years, and 91.3% of the reported cases were concentrated in August, September, and October. Based on an analysis of epidemiological survey reports, the main presumed infection route for confirmed patients was seafood consumption. It was the most common (42 [61.8%]) and there were also five (7.4%) cases presumed to have been infected after wounded skin was exposed to seawater. Additionally, 92.6% of the deceased had underlying diseases, such as liver disease, diabetes, and alcoholism. The number of patients with V. vulnificus sepsis in 2023 increased by approximately 1.5 times compared to the previous year, but the demographic and epidemiological characteristics of the confirmed patients were similar to those previously reported. The results of an annual surveillance project, including patient epidemiological characteristics and infection route analysis, is expected to serve as a basis for the prevention and management of V. vulnificus sepsis in the future.
Keywords: Vibrio vulnificus infection, Vibrio vulnificus, Consumption of seafood, Underlying diseases
Key messages
① What is known previously?
Vibrio vulnificus sepsis mainly occurs during the summer and has a high fatality rate of approximately 40%. The main routes of infection include consumption of contaminated seafood or shellfish and exposure of skin wounds to seawater.
② What new information is presented?
In 2023, the incidence of V. vulnificus sepsis increased significantly, with a notable occurrence during August, September, and October, comprising approximately 91.3% of cases.
③ What are implications?
While V. vulnificus sepsis is known to occur predominantly during summer. A trend towards prolonged epidemic periods was observed. Therefore, it is crucial to avoid consumption of contaminated seafood and shellfish, particularly people with underlying diseases, such as liver disease, diabetes and alcoholism.
Introduction
Vibrio vulnificus sepsis is a disease caused by V. vulnificus that can progress to sepsis, and it is designated as a class 3 infectious disease subject to comprehensive surveillance in the Republic of Korea (ROK) [1]. As a halophilic bacterium, V. vulnificus primarily inhabits various marine environments such as seawater, estuaries, and tidal flats owing to its requirement for appropriate salinity. It proliferates when the seawater temperature is above 18℃. The main routes of infection for V. vulnificus sepsis include the consumption of raw or undercooked contaminated seafood or contact of open wounds on the skin with contaminated seawater. It is known that person-to-person transmission of V. vulnificus does not occur. Individuals with underlying conditions such as chronic liver disease, diabetes, alcoholism, and immunodeficiency disorders are at higher risk of V. vulnificus infection [1-4]. Therefore, in this study, we aimed to analyze the epidemiological characteristics of confirmed cases of and deaths due to V. vulnificus sepsis in the ROK in 2023. Through this analysis, we sought to identify changes in infection routes and risk factors of V. vulnificus sepsis, with the goal of using this information as evidence for future prevention and management strategies for V. vulnificus sepsis.
Methods
1. Participants
The demographic characteristics of 69 patients (including 68 confirmed patients and 1 suspected patient) with V. vulnificus sepsis reported in the Disease and Health Integrated Management System (https://is.kdca.go.kr/) in 2023 were analyzed. The epidemiological characteristic analysis was conducted for the 68 patients with confirmed disease among them. Regarding the cases of death, the analysis was conducted for 27 individuals classified as having died due to V. vulnificus sepsis according to epidemiological investigations and the judgment of attending physicians from among the deaths reported in the Disease and Health Integrated Management System.
2. Data Collection and Analysis
The data on patients in 2023 were collected through the epidemiological survey registered in the Disease and Health Integrated Management System, and those on the annual incidence trend were collected from the Infectious Disease Portal. The information collected was analyzed using Microsoft Excel 2016.
Results
1. Incidence Characteristics
In 2023, there were 68 confirmed cases and 1 suspected case of V. vulnificus sepsis, showing an approximately 1.3-fold increase when compared with the 5-year average of 51.4 cases from 2018 to 2022. The analysis of incidence by month in 2023 revealed that from January to August, the incidence was 0.8 times lower than the average for the previous 5 years. However, the incidences in September and October were 1.6 and 2.7 times higher than the average for the previous 5 years. Compared with the previous 5-year period during which 43.6% of cases were reported from September to October, there was an increase in 2023, with 69.1% of cases reported during the corresponding period (Figure 1).
Figure 1. Number of reported cases with Vibrio vulnificus sepsis by month, 2023.
In 2023, the average age of the patients with V. vulnificus sepsis was 66.0 years (range, 33–92 years), which was higher than the average for the previous 5-year period (62.1 years). Compared with the previous 5-year average, in 2023, there was a 1.1-, 1.4-, and 1.7-fold increase in the incidence of V. vulnificus sepsis in the age groups of 50–59, 60–69, and ≥70 years, respectively; additionally, the incidence was the highest in the age group of ≥70 years, followed by the age groups of 60–69 and 50–59 years (Figure 2). In terms of the sex of the individuals affected in 2023, there were 52 male and 17 female patients, with the incidence in the former group being 3.1 times that in the latter group. Further, in 2023, there was a 1.3- and 1.5-fold increase in the incidence among male and female patients, respectively, compared with the corresponding averages in the previous 5-year period (Figure 2).
Figure 2. Number of reported cases with Vibrio vulnificus sepsis by age, 2023.
In terms of residence areas, the number of cases of V. vulnificus sepsis was the highest in Jeollanam-do (13 cases), followed by Seoul and Gyeongsangnam-do (9 cases each) and Incheon (8 cases). The incidence rate per 100,000 population nationwide was 0.13 cases, while by region, Jeollanam-do had the highest incidence rate (0.71), followed by Gyeongsangnam-do and Incheon (0.27 each) and Chungcheongnam-do (0.24; Figure 3).
Figure 3. Regional crude incidence rate of Vibrio vulnificus sepsis per 100,000 population by patientby registrated address.
2. Analysis of Epidemiological Characteristics
The main symptoms of V. vulnificus sepsis were fever (43 cases, 63.2%), followed by myalgia (20 cases, 29.4%), skin symptoms (19 cases, 27.9%), and shock (17 cases, 25.0%). The most common presumptive route of infection among confirmed patients was seafood consumption (42 patients, 61.8%). Thirty-six affected individuals (52.9%) were confirmed to have consumed raw seafood, with raw fish being the most common cause (27 cases, 39.7%). Five patients (7.4%) were presumed to have been infected by contact with seawater through wounds: one was found to be a person with an allergic skin disease who was exposed to seawater and four were found to have been exposed to seawater through wounds during work (e.g., fishing). Among the patients, there were 21 cases in which the presumptive source of infection could not be identified during the epidemiological investigation owing to death or loss of consciousness. Among the confirmed patients, 53 (77.9%) were confirmed to have underlying medical conditions. Liver disease was the most prevalent comorbidity, observed in 33 patients (48.5%), followed by diabetes, alcohol dependence, and kidney disease (Table 1).
Table 1. Epidemiological characteristics of the confrimed cases of the Vibrio vulnificus sepsis.
| Classification | Confirmed cases |
|---|---|
| Clinical symptoms and signs | |
| Sub total | 68a),b) |
| Fever | 43 (63.2) |
| Myalgia | 20 (29.4) |
| Skin lesion (papule, ulcer, bullae) | 19 (27.9) |
| Shock | 17 (25.0) |
| Diarrhoea | 14 (20.6) |
| Watery diarrhoea | 11 (16.2) |
| Bloody diarrhoea | 1 (1.5) |
| Cellulitis | 14 (20.6) |
| Stomach pain | 14 (20.6) |
| Nausea | 11 (16.2) |
| Vomiting | 11 (16.2) |
| Headache | 6 (8.8) |
| Others (chilling, mental deterioration, edema, etc.) | 24 (35.3) |
| Known exposures to infection | |
| Sub total | 68a) |
| Consuming sea food (raw food) | 36 (52.9) |
| Fish | 27 (39.7) |
| Crab | 2 (2.9) |
| Shrimp | 6 (8.8) |
| Oyster | 1 (1.5) |
| Consuming sea food (cooked food) | 6 (8.8) |
| Fish | 3 (4.4) |
| Shrimp | 2 (2.9) |
| Other types of shellfish | 1 (1.5) |
| Exposure to the seawater through skin lesion | 5 (7.4) |
| Unknownc) | 21 (30.9) |
| Underlying disease | |
| Sub total | 68a) |
| Liver disease | 33 (48.5) |
| Liver cirrhosis | 24 (35.3) |
| Alcoholic liver disease | 12 (17.6) |
| Hepatitis B | 6 (8.8) |
| Hepatitis C | 1 (1.5) |
| Other liver disease | 3 (4.4) |
| Diabetes | 13 (19.1) |
| Hypertension | 3 (4.4) |
| Other cancer | 6 (8.8) |
| Any types of hematological disease | 4 (5.9) |
| Any types of renal disorder | 9 (13.2) |
| Alcholism | 10 (14.7) |
| Skin injury | 6 (8.8) |
| No underlying disease | 13 (19.1) |
| Unknown underlying disease | 2 (2.9) |
Unit: person (%). a)Multiple responses were allowed. b)Including 2 cases in which the pattern of diarrhea could not be confirmed due to patient loss of consciouness or death. c)Unable to confirm due to patient loss of consciouness or death.
3. Analysis of Death Characteristics
Among the confirmed cases of V. vulnificus sepsis in 2023, a total of 27 deaths were attributed to V. vulnificus sepsis, based on epidemiological investigations and the judgment of attending physicians, resulting in a fatality rate of 39.1%. The distribution of the deaths by sex and age is shown in Table 2. In male patients, there were 23 deaths, approximately 5.8 times higher than that among female patients. With regard to age, 8, 7, and 7 of the patients who died were in their 50s, 60s, and ≥70 years, respectively. The main symptoms of the deceased were fever (14 patients), shock (12 patients), and muscle pain (10 patients). Of those who died, 25 (92.6%) had underlying conditions and two had no confirmed underlying health conditions. Among the underlying diseases, liver disease, including hepatitis B, alcoholic hepatitis, and cirrhosis, was the most common (18 patients, 72.0%), followed by diabetes and alcoholism in 6 patients each (24.0%). The most common routes of infection among the deceased were seafood consumption (15 cases, 55.6%), followed by raw food consumption (11 cases, 40.7%) and fish consumption (8 cases, 29.6%). There were 11 cases of death in which the presumptive routes of infection could not be determined (Table 3).
Table 2. Demographic characteristics of the deaths of the Vibrio vulnificus sepsis.
| Classification | Deaths (n=27) |
|---|---|
| Sex | |
| Male | 23 (85.2) |
| Female | 4 (14.8) |
| Age (yr) | |
| 30–39 | 2 (7.4) |
| 40–49 | 3 (11.1) |
| 50–59 | 8 (29.6) |
| 60–69 | 7 (25.9) |
| ≥70 | 7 (25.9) |
| Confirmed month | |
| June | 1 (3.7) |
| July | 2 (7.4) |
| August | 5 (18.5) |
| September | 11 (40.7) |
| October | 8 (29.6) |
Unit: person (%).
Table 3. Epidemiological characteristics of the deaths of the Vibrio vulnificus sepsis.
| Classification | Deaths |
|---|---|
| Clinical symptoms and signs | |
| Sub total | 27a),b) |
| Fever | 14 (51.9) |
| Shock | 12 (44.4) |
| Myalgia | 10 (37.0) |
| Skin lesion (papule, ulcer, bullae) | 8 (29.6) |
| Stomach pain | 6 (22.2) |
| Diarrhoea | 5 (18.5) |
| Watery diarrhoea | 4 (14.8) |
| Vomiting | 5 (18.5) |
| Cellulitis | 4 (14.8) |
| Nausea | 3 (11.1) |
| Headache | 2 (7.4) |
| Others (mental deterioration, edema, etc.) | 14 (51.9) |
| Known exposures to infection | |
| Sub total | 27a) |
| Consuming sea food (raw food) | 11 (40.7) |
| Fish | 8 (29.6) |
| Crab | 1 (3.7) |
| Other types of shellfish | 2 (7.4) |
| Consuming sea food (cooked food) | 4 (14.8) |
| Fish | 3 (11.1) |
| Other types of shellfish | 1 (3.7) |
| Exposure to the seawater through skin lesion | 1 (3.7) |
| Unknownc) | 11 (40.7) |
| Underlying disease | |
| Sub total | 25a),d) |
| Liver disease | 18 (72.0) |
| Alcoholic liver disease | 11 (44.0) |
| Liver cirrhosis | 12 (48.0) |
| Hepatitis B | 4 (16.0) |
| Hepatitis C | 1 (4.0) |
| Diabetes | 6 (24.0) |
| Hypertension | 2 (8.0) |
| Other cancer | 4 (16.0) |
| Any types of hematological disease | 1 (4.0) |
| Any types of renal disorder | 4 (16.0) |
| Alcholism | 6 (24.0) |
| Skin injury | 2 (8.0) |
Unit: person (%). a)Multiple responses were allowed. b)Including 1 case in which the pattern of diarrhea could not be confirmed. c)Unable to confirm due to patient loss of consciouness or death. d)Excluding 2 deaths with unconfirmed underlying disease.
Discussion
This report presents the results of an analysis of the epidemiological characteristics of confirmed cases of and deaths due to V. vulnificus sepsis. The analysis was performed using data recorded in the Disease and Health Integrated Management System in 2023, along with epidemiological investigation data. The number of cases of V. vulnificus sepsis was 69 (68 confirmed cases and 1 suspected case), which was approximately 1.3 times higher than the average of 51.4 in the last 5 years. However, the fatality rate in 2023 was 39.1%, similar to that in the previous year.
The number of confirmed cases was approximately three times higher in male patients than in female patients, which was consistent with other research findings. However, the V. vulnificus sepsis susceptibility difference between the sexes remains unclear [5]. All confirmed cases were in people older than 30 years, and the average age of the affected individuals in 2023 was higher than the average for the last 5 years. In most foreign cases, the predominantly affected age group was 50–70 years. In July and August 2023, the median age of 11 confirmed patients in the United States was 70 years (range, 37–84 years) [5-9]. In the ROK, the highest incidence was found in the Jeollanam-do, and it was confirmed the affected patients mainly lived near the coast (Figure 3), which is similar to the findings reported overseas [6,9].
In terms of clinical symptoms, the most common ones among the confirmed patients were fever, followed by myalgia and skin symptoms, and among those who died, the most common symptoms were fever, shock, and myalgia, in that order. This can be explained by the findings of a previous study that reported that most patients with V. vulnificus sepsis experienced fever and chills and that when sepsis developed, the patients’ blood pressure decreased by 60–70% [7].
Underlying conditions are significant risk factors that increase the risk of V. vulnificus sepsis and associated mortality. The 2023 epidemiological investigation results showed that 77.9% of the confirmed patients had underlying conditions, and notably, 92.6% of the deceased had underlying conditions. The main underlying conditions included liver diseases such as alcoholic liver disease, hepatitis B, and hepatitis C. This can be interpreted as an increased risk of infection with V. vulnificus owing to the immune suppression caused by these underlying conditions. Therefore, it is especially important for people with underlying conditions to strictly adhere to preventive measures for V. vulnificus sepsis [2-10].
Among the patients with V. vulnificus sepsis, 42 developed symptoms after consuming seafood (raw or cooked), with the majority consuming raw seafood. Symptoms also developed among those who had consumed contaminated seafood. This suggests an epidemiological association between consuming seafood and V. vulnificus sepsis, as described in the 2020 epidemiological report [2]. While consuming seafood contaminated with V. vulnificus remains a significant risk factor, recent reports from other countries have highlighted cases of infection through skin wounds during seafood handling [9]. Additionally, in 2023, cases were reported where individuals, particularly those involved in fishing, were infected through skin wounds exposed to seawater in the ROK. Therefore, special attention should be paid to this aspect.
In 2023, 91.3% of V. vulnificus sepsis cases occurred between August and October, and the number of patients in October was approximately 2.7 times higher than the average in the previous 5 years. Previous studies have shown that the incidence of V. vulnificus sepsis is clearly seasonal, influenced by sea temperatures [6], and the bacterium can proliferate maximally when the seawater temperature is above 25℃ [11]. Recently, the temperature of the seawater surrounding the Korean Peninsula has been increasing, reaching 25℃ or higher in August and September [12]. Considering future climate change, there is a possibility of an increase in V. vulnificus sepsis cases, indicating the need for continuous monitoring. Reports from the World Health Organization and the Food and Agriculture Organization of the United Nations also emphasized that climate change is resulting in a favorable environment for the growth of V. vulnificus as the temperature of seawater increases. Hence, it is necessary to predict changes in the proliferation of V. vulnificus and to continue implementing countermeasures to prevent V. vulnificus sepsis [10].
There are still limitations in interpreting the causes for the increase in the incidence of patients in this study in relation to climate factors such as sea temperature. Hence, in the long term, it is necessary to analyze the incidence trend of V. vulnificus sepsis due to environmental factors, in conjunction with the results of the Vibrio-Net project (Surveillance project for Pathogenic V. vulnificus in Marine Environments) conducted by the Korea Disease Control and Prevention Agency.
There was no significant change in the demographic or epidemiological characteristics of V. vulnificus sepsis cases in 2023, and as previously known, underlying conditions such as liver disease and consumption of contaminated seafood were major risk factors. Therefore, individuals with underlying conditions that may reduce immunity, such as liver disease and diabetes, should be particularly cautious about consuming seafood from June to October. Additionally, individuals with open wounds need to take extra precautions to avoid exposure to seawater. In addition, if there is a suspicion of clinical symptoms such as fever, muscle pain, and skin symptoms, it is necessary to immediately visit a medical institution for active treatment.
The Korea Disease Control and Prevention Agency will continue to monitor the incidence of V. vulnificus sepsis, analyze epidemiological characteristics, and promote active prevention and control policies to prevent infection with V. vulnificus in advance.
Acknowledgments
None.
Funding Statement
Funding Source: None.
Declarations
Ethics Statement: Not applicable.
Conflict of Interest: The authors have no conflicts of interest to declare.
Author Contributions: Conceptualization: SKP, SYP. Data curation: SKP. Formal analysis: SKP. Investigation: SKP, HJK. Methodology: HJK, JSY. Project administration: SYP, JSY. Resources: SKP. Supervision: SYP. Visualization: SCY. Writing – original draft: SKP. Writing – review & editing: SYP, SCY, HJK, JSW.
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