a. Malaria incidence per age group in children 0 to 14 years old.
From November 2018 to October 2020, 42,248 patients visited the pediatric department of SDH and 21,663 (51.2 %) were positive to malaria. From the malaria positive patients 89.9 % were from the Sussundenga municipality.
The incidence per 45.7 per 100 persons for year 2019 patients. As per gender, the malaria positive patients were 48.4 % male and 51.6 % females.
The average age of pediatric malaria patients was 5.7 SD (Standard deviation) = 1.38 years. Figure 2 presents age group distribution and, age group 0 to 5 month presented the least percentage of cases 3.3 % while, the age group 5 to 14 years old presented the highest percentage of cases 45.6 %. No difference was found between sex among the age categories.
b. Malaria incidence by residential areas
The incidence per residential area varied from 6.6 per 100 persons to 118 per 100 persons. There is a difference between residential areas in malaria incidence G = 377.38, P = 0.0001, DF = 16 and, Nhamarenza present the highest incidence, 118 per 100 persons, and the least incidence was presented in residential areas Chizizira and Tave with 6.6 and 6.7 per 100 persons respectively (Figure 3).
c. Malaria cases by month
Figure 4 presents the percentage malaria pediatric cases for 2019. January presented the highest percentage of cases 19.7 % followed by May 19.6 % and, the least percentage of cases occurred in September, 0.1 %.
d. Malaria risk mapping
i. Analytical Hierarchical Process and consistency check
Table 2 and 3 presents the comparison matrix of 10 x 10 and, 9 x 9 risk factors that were used. A value of 1 means that the malaria risk factors that are being compared have the same weight. A value of 4 for example a malaria risk factor in the column is four times more important in the malaria cases occurrence. The consistence ratio was 0.081 and 0.096 for 10 x 10 and 9 x 9 matrix respectively considered good enough.
Mapping risk of malaria and accuracy check.
Figure 5 presents the risk factor maps before reclassification. The average temperature in the area varies from 20.14 to 21.17 oC, the rainfall from 1028 to 1,082.24 mm, altitude from 459 to 791 meters, slope from 0 to 37.5 o, distance to water bodies from 0 to 15,134 meters, NDVI from -0.14 to 0.5, population density from 41 to 59,091 persons per Km2, malaria incidence from 2.9 to 118 persons per 100 and distance to roads from 0 to 13,510.7 meters.
Figure 6 presents the maps for the reclassified risk factors and the malaria risk in percentage. Rainfall (100 %) and slope (73 %) has the highest risk, altitude (100 %) and NDVI (92 %) has the moderate risk in the municipality.
The spatial model derived to produce the two malaria risk maps from the risk factors are presented in formula 1 and 2.
\(Map=\left(Temperature x 0.2259\right)+\left(Rainfall x 0.2001\right)+\left(altitude x 0.127\right)x \left(DTWB x 0.0936\right)+\left(slope x 0.0828\right)+\left(LULC x 0.0646\right)+\left(population density x 0.0646\right)+ \left(DTR x 0.0486\right)+\left(incidence x 0.0473\right)+\left(NDVI x 0.03\right)\) (1).
\(Map=\left(Temperature x 02183\right)+\left(Rainfall x 0.2105\right)+\left(altitude x 0.1377\right)x \left(DTWB x 0.0936\right)+\left(slope x 0.10\right)+\left(LULC x 0.0935\right)+\left(population density x 0.0624\right)+ \left(DTR x 0.0432\right)+\left(NDVI x 0.037\right)\) (2).
Figure 7A and Figure 6B presents the final malaria risk maps for Sussundenga municipality after the consolidation and the weighting using the incidence data and, excluding the incidence data. The entire Sussundenga municipality his at risk of malaria varying from moderate to high risk. Malaria high risk seems to coincide with highly populated area and around waterbodies.
Table 4 presents the percentage of malaria risk in Sussundenga and there is now difference in the risk areas using and, excluding the clinical data (incidence data).
Table 4A and B presents the area of the high and moderate malaria risks
A. Including Incidence B. Excluding Incidence.
In this study the pediatric malaria weight of malaria was 51.2 %. In 2015 malaria was responsible for 45 % of outpatient visits and 56 % of pediatric admissions in Mozambique  consistency with these results. A study in Manhiça, a rural area in the south of Mozambique in 2008  indicated 30.5 % had malaria, lower than the results of the present study and, this can be related to environmental conditions since the south of Mozambique is more arid. In Malawi a neighboring country the weight of de disease ranged from 26 % in Salima to 64 % in Mwanza .
The malaria incidence in pediatric malaria in this study was 45.7 per 100 persons. A 2018 study reported an incidence of 39 per 100 in children under 10 years in the Central region of Mozambique . A study in Malawi indicated 35 to 37 per 100-person incidence in children under 15 in 2017 . In Zimbabwe significant progress was made in malaria cases reduction and the incidence is of 2.5 per 100 persons while, in Zambia is of 20 per 100 persons [25,26].
The mean age of malaria patients in this study was 5.6 SD 1.3 years. In Southern Africa a review of 29 studies in 2010 reported a median age of clinical malaria of 32 month highly intense and not markedly seasonal transmission areas and 72 months in settings of low intensity and markedly seasonal transmission area consistent to this study . In China the mean average of most childhood diseases was reported to range from 20 to 80 months and, for high incidence pediatric disease approximately 3 years .
In this study, the age group 5 to 14 years old presented the highest percentage of cases 45.6 % while this category comprises 30.2 % of the municipality inhabitants. A community study in the same municipality in 2021 reported 50 % of positive cases of malaria in children aged 5 to 14 years  consistent with these results. A study in Manhiça Mozambique  reported 36 % of cases among age group 5 to 14 in 2008 less than in this study and, while, a study in Inhambane, Mozambique  in 2015, reported higher figure of 67.7 %. In Malawi and Kenya results consistent with the present findings were reported [31,32].
A shift in the peak age of cases from 1 – 4 years old to 5 to 9 years old was reported in 2009 in a study in Inhambane, Mozambique . In many malaria-endemic areas, successful control programs have reduced the level of transmission substantially and consequently, in such communities, the peak age of clinical attacks of malaria is shifting from very young to older children [33, 34, 35].
The least malaria cases in this study occurred in children aged 0 to 5 months. For approximately six months after birth, antibodies acquired from the mother during pregnancy protect the child. This maternal immunity is gradually lost as the child begins to develop his or her own immunity to malaria. In areas where malaria is endemic, children are believed to achieve a high level of immunity up to 5 years of age [36,37]. Higher usage of bed nets was also reported in pregnant mothers and children less than one year than in children 5 to 14 years [30, 36].
In this study, there was a difference in malaria incidence between residential areas varying from 6.6 to 118 per 100 persons. The results are consistent with studies in Chimoio, Sussundenga and, in Mozambique [4, 6, 29, 37, 38]. In Ethiopia and Kenya spatial variation of malaria incidence in a geographically homogeneous area was also reported [39, 40} and, this can be a result of high endemicity. Heterogeneous rates from 2.5 to 10.5 episodes per 100 children year was also reported in Senegal . In Malawi, geographical groups of households where children experienced repeated malaria infections overlapped with high mosquito’s density areas . In Brazil, the high incidence of malaria at low scale was due to the heavily modified landscape .
Most malaria cases occur from January to March in Mozambique [5, 6]. For 2019 the high malaria cases prolonged from January to May. This is a result of the Cyclone IDAI that occurred in March 2019 that resulted in heavy rain and floods in the region. The malaria temporality was also reported in other countries in Africa .