Data from 77,405 malaria cases reported to the Malaria Information System (MIS) were split into 24,332 (31.4%) cases for FY 2015; 17,578 (22.7%) cases for the FY 2016 transition period; and 35,495 (45.9%) cases for the FY 2017–FY 2021 post-intervention period. Adherence and achievement analyses included all cases with complete data on 1-3-7 indicators, which were available for 15,887 (90.4%) of FY 2016 cases and 32,957 (92.9%) of FY 2017–FY 2021 post-intervention cases; the remainder were not included for analysis due to missing or duplicate data. Recurrences were treated as new cases for the purpose of this study.
Adherence to 1-3-7 protocols
Adherence to case notification within 1 day
The monthly proportion of confirmed malaria cases reported within 24 hours to the system increased over the study period, from 18.2% in October 2016 to 80.7% in September 2021 (Figure 2). This increase was steady despite the fact that reporting rates vary based on malaria seasonality. During the peak transmission month of June, the proportion of timely notification increased steadily from 30.1% in FY 2017 (567/1,881) to 92.6% in FY 2020 (823/889) and 88.0% in FY 2021 (462/525). Note that there was a temporary drop of the timely notification proportion, to 56.2% at the end of FY 2019, due to an MIS database security breach in August 2019 that temporarily disabled data entry. However, the DVBD was quick to respond to the issue, so malaria officers inputted data retrospectively, data entry was quickly resumed, and delays in reporting were limited to only two months (25).
Adherence to case investigation within 3 days
The monthly proportion of malaria cases investigated improved from 73.8% in October 2016 to 97.8% by September 2021, with substantial growth each year (Figure 3). The proportion of case investigations within the 3-day requirement also improved over time, from 52.4% in June 2017 to 91.9% by September 2021, even after seasonality is considered. The proportion of malaria cases investigated during the peak season in June rose from 64.1% (1,206/1,881) in FY 2017 to 97.3% (511/525) in FY 2021. During the low transmission season, case investigation followed the same upward trend, rising from 72.7% (421/579) in FY 2017 to 99.3% (139/140) in FY 2021. Reporting timeliness also increased from 52.4% and 56.1% in the FY 2017 peak and low seasons, respectively, to 95.6% and 96.4% in the FY 2021 peak and low seasons, respectively.
Adherence to foci investigation and response within 7 days
The monthly proportion of RACD conducted among the cases that required RACD improved substantially over the study period, from 56.5% in October 2016 to 83.2% by September 2021 (Figure 4). The proportion of RACD events conducted on time (within 7 days of case notification) also made dramatic improvement over the study period, from 48.2% to 80.3%. These proportions did not vary much between high and low transmission seasons. However, adherence rates were higher in FY 2020 than FY 2021, likely due to COVID-related movement restrictions that compromised access to rural communities.
Comparison by area classification
Comparative t-tests showed that adherence to the DVBD’s timeliness protocols did not show statistically significant variation by area classification. Before and during the buffer year of 1-3-7 implementation, timely case reporting was higher among active foci than among cleared foci with an index case (p < 0.05). Although active foci continued to show more timely surveillance and response than cleared foci, in the post-intervention period, these differences were not statistically significant.
Achievements of the 1-3-7 surveillance strategy compared to national targets
The second part of this analysis compared actual results to targets laid out by FY, divided into output results and outcome/impact results (see Table 2 for summarized results). The NMES uses FY 2015 as a baseline year.
Output indicators
Overall, results on output indicators were strong. First, malaria cases reported in the MIS within the 1-day (or 24-hours) period showed consistent improvement over time, with rates reaching targets in FY 2019, FY 2020, and FY 2021 (77.1%, 87.8%, and 89.3%, respectively). Second, the proportion of cases investigated within 3 days dramatically increased from baseline to 96.5%, exceeding the FY 2021 target (95%). Lastly, for foci investigation and response conducted within 7 days, the outputs met the targets in every FY, with the FY 2020 and FY 2021 proportions of 84.1% and 87.2% both surpassing the FY 2021 target.
The authors also examined the supplemental output indicators for which targets were not defined in the NMES, with results summarized in Table 3. During FY 2017–FY 2021, 14,277index cases triggered RACD (83.3% of total cases eligible for RACD), leading to 866,920 people being screened: 1,513 (0.17%) were positive for malaria infection. Each year, the number of individuals screened during RACD events dropped, with the proportional yield of positive cases also decreasing from 0.23% in FY 2017 to 0.11% in FY 2021. RACD methods produced nearly equal yields for both active foci and cleared foci with a confirmed index case (0.19% versus 0.16%).
Outcome/impact indicators
For the outcome indicator of percentage of districts without local transmission for at least three years (among a total of 928 districts in Thailand), targets were reached every FY between 2017 and 2019 (80%, 83%, and 85% respectively). Progress plateaued in FY 2020 and FY 2021, whereby district achievement reached 86% and 85%, missing the 90% and 95% targets, respectively. The second outcome indicator is the number of villages with malaria transmission, which dropped from 2,310 in FY 2017 to 469 in FY 2021 (Table 2). This indicator has shown better-than-expected results, with substantial reductions beyond the set target each year, showing strides in interrupting community transmission.
These results were supplemented by other data collected by the DVBD on the population at risk in active foci, which from FY 2017 to FY 2021 dropped from 766,548 to 287,464 (Figure 5), and a decrease in the number of active foci from 2,310 to 469 for the same period. Because the DVBD’s unit of analysis for daily assessments of routine data was the focus level, the program’s MIS collated more granular geotemporal data on malaria-free area classification than what was required for NMES reporting.
Observed and predicted trend in incidence
The annual positive rates of all malaria species were used to establish an ARIMA model in active foci areas (R2 = 0.72) (Figure 6). Prior to the 1-3-7 strategy’s launch, malaria incidence among active foci was decreasing annually by 1.02 per 1,000 population at risk. After the launch in FY 2016, the ARIMA model showed an additional reduction to 1.31 cases per 1,000 population at risk per year. Each subsequent year has seen further reductions, averaging 1.36 (p = 0.62) annually, indicating an acceleration in the reduction of malaria incidence during the implementation period. The trend is forecasted to continue through FY 2024.
Spatial analyses among active foci
During the study period, active foci were clustered at Thailand’s international borders. Adherence to 1-3-7 protocols showed a marked spatial heterogeneity among active foci (Figure 7), with southern and eastern foci reporting lowest adherence. Among the indicators examined, timely case investigation showed the highest results and lowest spatial heterogeneity (Figure 7); however, some foci in high-burden areas in the northwest showed poor adherence (p < 0.05). The G* test identified foci with significantly (p < 0.05) lower adherence to overall 1-3-7 timeliness, mostly in Sisaket province in the east, Kanchanaburi and Ratchaburi provinces in the west, and Yala province in the south. (Figure 8).