Factors associated with the timely diagnosis of malaria and the utilization of types of healthcare facilities: a retrospective study in the Republic of Korea

BACKGROUND

This study aimed to analyze trends in the timely diagnosis of malaria cases over the past 10 years in relation to the utilization of different types of healthcare facilities.

METHODS

The study included 3,697 confirmed and suspected cases of malaria reported between January 1, 2013, and December 31, 2022, in the national integrative disease and healthcare management system. Some cases lacking a case report or with information missing from the case report were excluded from the analysis. A generalized linear model with a Poisson distribution was constructed to estimate risk ratios and 95% confidence intervals adjusted for other variables, such as distance.

RESULTS

When cases involving diagnosis >5 days after symptom onset in confirmed patients (5DD) were examined according to the type of healthcare facility, the risk ratio of 5DD cases was found to be higher for tertiary hospitals than for public health facilities. Specifically, the risk ratio was higher when the diagnosis was established at a tertiary hospital, even after a participant had visited primary or secondary hospitals. In an analysis adjusted for the distance to each participant's healthcare facility, the results did not differ substantially from the results of the crude analysis.

CONCLUSION

It is imperative to improve the diagnostic capabilities of public facilities and raise awareness of malaria at primary healthcare facilities for effective prevention and control.

Species Diversity of Anopheles Mosquitoes and Plasmodium vivax Infection Rates, Gyeonggi Province, Republic of Korea During 2020

There are currently >300 malaria cases reported annually in the Republic of Korea (ROK), with most cases attributed to exposure in northern Gangwon and Gyeonggi provinces near the demilitarized zone (DMZ). The species diversity and malaria infection rate were determined for a sample of Anopheles mosquitoes collected from May to early November 2020 for six sites in a malaria high-risk area in/near the DMZ and two malaria low-risk areas in southern Gyeonggi province using Mosquito Magnet traps in the ROK. A total of 1864 Anopheles spp. were identified to species by PCR. Overall, An. kleini (31.4%, 510/1622) was the most frequently species assayed, followed by An. pullus (25.5%, 413/1622), An. sineroides (23.9%, 387/1622), and An. sinensis (10.2%, 165/1622), while the other four species only accunted for 9.1% (147/1622) collected in/near the DMZ. Only three species, An. pullus, An. sinensis, and An. sineroides were collected at Humphreys US Army Garrison (USAG) (235 individuals), while only An. sinensis was collected at Yongsan USAG (7 individuals). A total of 36 Anopheles specimens belonging to five species collected in/near the DMZ were positive for Plasmodium vivax by PCR. Anopheles kleini (9) was the most frequent species positive for P. vivax, followed by An. belenrae (8), An. pullus (8), An. sinensis (5), An. sineroides (5), and a member of the Anopheles Lindesayi Complex in the ROK (1). This is the first report of P. vivax in a member of the An. Lindesayi Complex in the ROK. These findings can assist in guiding future malaria vector management in the ROK.

Changing Disease Trends in the Northern Gyeonggi-do Province of South Korea from 2002 to 2013: A Big Data Study Using National Health Information Database Cohort

Objectives

To investigate the chronological patterns of diseases in Northern Gyeonggi-do province, South Korea, and compare these with national data.

Methods

A National Health Insurance cohort based on the National Health Information Database (NHID Cohort 2002–2013) was used to perform a retrospective, population-based study (46,605,433 of the target population, of which 1,025,340 were randomly sampled) to identify disease patterns from 2002 to 2013. Common diseases including malaria, cancer (uterine cervix, urinary bladder, colon), diabetes mellitus, psychiatric disorders, hypertension, intracranial hemorrhage, bronchitis/bronchiolitis, peptic ulcer, and end stage renal disease were evaluated.

Results

Uterine cervix cancer, urinary bladder cancer and colon cancer had the greatest rate of increase in Northern Gyeonggi-do province compared with the rest of the country, but by 2013 the incidence of these cancers had dropped dramatically. Acute myocardial infarction and end stage renal disease also increased over the study period. Psychiatric disorders, diabetes mellitus, hypertension and peptic ulcers showed a gradual increase over time. No obvious differences were found for intracranial hemorrhage or bronchitis/bronchiolitis between the Northern Gyeonggi-do province and the remaining South Korean provinces. Malaria showed a unique time trend, only observed in the Northern Gyeonggi province, peaking in 2004, 2007 and 2009 to 2010.

Conclusion

This study showed that the Northern Gyeonggi-do province population had a different disease profile over time, compared with collated data for the remaining provinces in South Korea. “Big data” studies using the National Health Insurance cohort database can provide insight into the healthcare environment for healthcare providers, stakeholders and policymakers.

Future climate data from RCP 4.5 and occurrence of malaria in Korea

Since its reappearance at the Military Demarcation Line in 1993, malaria has been occurring annually in Korea. Malaria is regarded as a third grade nationally notifiable disease susceptible to climate change. The objective of this study is to quantify the effect of climatic factors on the occurrence of malaria in Korea and construct a malaria occurrence model for predicting the future trend of malaria under the influence of climate change. Using data from 2001–2011, the effect of time lag between malaria occurrence and mean temperature, relative humidity and total precipitation was investigated using spectral analysis. Also, a principal component regression model was constructed, considering multicollinearity. Future climate data, generated from RCP 4.5 climate change scenario and CNCM3 climate model, was applied to the constructed regression model to simulate future malaria occurrence and analyze the trend of occurrence. Results show an increase in the occurrence of malaria and the shortening of annual time of occurrence in the future.

The Long and Short Incubation Periods of Plasmodium vivax Malaria in Korea: The Characteristics and Relating Factors

BACKGROUND

The cases of Plasmodium vivax malaria in Korea are mixed with long and short incubation periods. This study aims to define clinico-epidemiologic chracteristcs of Plasmodium vivax malaria in Korea.

MATERIALS AND METHODS

We selected the civilian cases infected with P. vivax malaria in Korea from the epidemiological investigation data of 2001 to 2010, whose incubation periods could be estimated. The long and short incubation periods were defined by duration of infection and onset time, and the cases were compared by demographic factors and clinical symptom, infection and onset time. The correlation was analyzed between the proportion of cases in the infected region with the long incubation period and meteorological factors along with latitude.

RESULTS

The length of the mean short and long incubation periods for the cases were 25.5 days and 329.4 days, respectively. The total number of the study subjects was 897, and the number cases of short and long incubation periods was 575 (64.1%) and 322 (35.9%), respectively. The aspect of incubation period showed a significant difference by region of infection; there was a higher proportion of long incubation period infection cases in Gangwon-do than in Gyeonggi-do and Incheon. The proportion of long incubation period cases showed significant correlation with latitude and temperature of August and September of the infected regions.

CONCLUSIONS

Incubation period of P. vivax malaria in Korea showed significant difference by infected region, infection and onset time and the proportion of long incubation period cases showed significant correlation with latitude and meteorological factors of the infected regions.

A case of Plasmodium ovale malaria imported from West Africa

Malaria is a parasitic infection caused by Plasmodium species. Most of the imported malaria in Korea are due to Plasmodium vivax and Plasmodium falciparum, and Plasmodium ovale infections are very rare. Here, we report a case of a 24-year-old American woman who acquired P. ovale while staying in Ghana, West Africa for 5 months in 2010. The patient was diagnosed with P. ovale malaria based on a Wright-Giemsa stained peripheral blood smear, Plasmodium genus-specific real-time PCR, Plasmodium species-specific nested PCR, and sequencing targeting 18S rRNA gene. The strain identified had a very long incubation period of 19-24 months. Blood donors who have malaria with a very long incubation period could be a potential danger for propagating malaria. Therefore, we should identify imported P. ovale infections not only by morphological findings but also by molecular methods for preventing propagation and appropriate treatment.

Clinical characteristics of vivax malaria and analysis of recurred patients

Background

Plasmodium vivax malaria is an acute debilitating illness characterized by recurrent paroxysmal fever and relapses from hypnozoites in the liver. Although a few studies reported clinical characteristics of vivax malaria in civilians after reemergence in the Republic of Korea, only a small group of patients was analyzed.

Materials and Methods

We retrospectively reviewed the medical records of patients who had been diagnosed with vivax malaria by peripheral blood smear in a university-affiliated hospital located in a malaria-endemic area between January 2005 and December 2009.

Results

During the study period, a total of 352 malarial cases from 341 patients were diagnosed. Vivax malaria was most commonly developed in July and August, 24.7% (87/352), and 21.9% (77/352), respectively. The mean (SD) age was 42.5 (14.7) years and the number of male patients was 243 (71.3%). Six patients had a previous history of vivax malaria from 6 months to 10 years before. A total of 337 patients (98.8%) had fever and the mean (SD) body temperature was 38.3 (1.4)℃. Common associated symptoms were chills (213/341, 62.5%), headache (115/341, 33.7%), and myalgia (85/341, 24.9%). Laboratory findings included thrombocytopenia (340/341, 99.7%), anemia (97/341, 28.5%), leukopenia (148/341, 43.4%), increase of aspartate transaminase (177/341, 51.9%), and increase of alanine transaminase (187/341, 54.8%). Hypotension (14/341, 4.1%), altered mentality (3/341, 0.9%), azotemia (3/341, 0.9%), spleen infarction (2/341, 0.6%), and spleen rupture (1/341, 0.3%) developed as complications. Chloroquine was administered to all patients and primaquine was administered with mean (SD) 3.39 (0.82) mg/kg to 320 patients. There were 11 recurrent infections during the study period. The median (range) time to recurrent infection was 100 (32-285) days. Platelet counts were higher (86,550 vs. 56,910/mm³) and time to treatment of malaria was shorter (5 vs. 7 days) in relapsed cases compared with first occurrence cases (P=0.046).

Conclusions

The overall recurrence rate of vivax malaria was 3.2% (11/341) in this study. In recurred cases, malaria was diagnosed earlier and thrombocytopenia was less severe. To evaluate the risk factors associated with recurrence and adequate dose of primaquine in Korean patients, further large-scale prospective studies will be needed.

[A case of malarial hepatitis by Plasmodium vivax]

Malarial infection is one of the most important tropical diseases, but also increasing in the temperate regions. Severe malaria with organ dysfunction is commonly associated with Plasmodium falciparum, but rarely with Plasmodium vivax. Malarial hepatitis is also unusual in P. falciparum and very rare in P. vivax. Only 3 cases of malarial hepatitis caused by P. vivax have been reported in the world. Because the presence of hepatitis in malaria indicates a more severe illness with higher incidence of other complications and poor prognosis, malarial patients should be meticulously monitored for hepatic dysfunction with or without jaundice. We report here a case of malarial hepatitis caused by P. vivax that was presented by fever, general ache, nausea, fatigue, and significant elevation of aminotransferase and bilirubin.

[Evaluation of usefulness of the panel test composed of malaria non-specific tests as a surrogate marker]

BACKGROUND

Although malaria-specific antibody or antigen test is useful for the diagnosis of malaria infection, its cost-effectiveness has to be concerned in the area where malaria prevalence is very low. We created a panel test composed of malaria non-specific parameters, namely hematology autoanalyzer-derived results with or without addition of HDL-cholesterol data, and evaluated its usefulness in comparison with malaria-specific antibody test.

METHODS

For 395 patients tested for malaria smear, the hematology parameters such as platelet count, NRBC (%) and VCS (volume, conductivity, scattering) parameters of WBC, and HDL-cholesterol data were analyzed. Statistical significance of each parameter and that of panel test with or without addition of HDL-cholesterol were evaluated.

RESULTS

Malaria antibody test showed sensitivity of 97.1% and specificity of 99.1%. Each parameter of platelet count, NRBC (%), D parameter and HDL-cholesterol showed sensitivity of 86.8%, 41.2%, 81.8%, and 70.6%, and specificity of 85.9%, 96.3%, 72.3%, and 81.7%, respectively. Panel test without including HDL-cholesterol showed sensitivity of 91.2% and specificity of 81.6%, and that including HDL-cholesterol showed sensitivity of 91.2% and specificity of 86.2%.

CONCLUSIONS

The malaria non-specific panel test composed of hematology autoanalyzer-derived parameters showed relatively good, but slightly lower sensitivity than that of malaria-specific antibody test. It might be used as a screening test for the diagnosis of malaria infection, and addition of HDL cholesterol improved little the usefulness of the panel test.