diff --git a/cpp/examples/graph_abm.cpp b/cpp/examples/graph_abm.cpp
index 9eb1caf65a..aca8763d65 100644
--- a/cpp/examples/graph_abm.cpp
+++ b/cpp/examples/graph_abm.cpp
@@ -51,17 +51,29 @@ struct Logger : mio::LogAlways {
     {
         Type location_information{};
         location_information.reserve(size_t(mio::abm::LocationType::Count));
-        auto t = sim.get_time();
-        for (auto&& loc : sim.get_model().get_locations()) {
-            std::map<mio::abm::InfectionState, size_t> persons_per_infection_state;
+        auto t             = sim.get_time();
+        const auto& model  = sim.get_model();
+        const auto num_loc = model.get_locations().size();
+
+        // Count the Persons per Location and InfectionState in a single pass over all Persons, instead of calling
+        // get_subpopulation for every Location and InfectionState, which iterates over all Persons each time.
+        std::vector<std::map<mio::abm::InfectionState, size_t>> persons_per_infection_state(num_loc);
+        for (auto& counts : persons_per_infection_state) {
             for (size_t i = 0; i < static_cast<size_t>(mio::abm::InfectionState::Count); ++i) {
-                auto inf_state = mio::abm::InfectionState(i);
-                persons_per_infection_state.insert(
-                    {inf_state, sim.get_model().get_subpopulation(loc.get_id(), t, inf_state)});
+                counts[mio::abm::InfectionState(i)] = 0;
+            }
+        }
+        for (auto&& person : model.get_persons()) {
+            // Persons currently located in another model are counted there
+            if (person.get_location_model_id() == model.get_id()) {
+                ++persons_per_infection_state[person.get_location().get()][person.get_infection_state(t)];
             }
+        }
+
+        for (auto&& loc : model.get_locations()) {
             location_information.push_back(std::make_tuple(loc.get_model_id(), loc.get_type(), loc.get_id(),
-                                                           sim.get_model().get_number_persons(loc.get_id()),
-                                                           persons_per_infection_state));
+                                                           model.get_number_persons(loc.get_id()),
+                                                           persons_per_infection_state[loc.get_id().get()]));
         }
         return location_information;
     }
diff --git a/cpp/models/abm/model.cpp b/cpp/models/abm/model.cpp
index a886edde98..0b1eac064a 100755
--- a/cpp/models/abm/model.cpp
+++ b/cpp/models/abm/model.cpp
@@ -380,18 +380,18 @@ LocationId Model::find_location(LocationType type, const PersonId person) const
 
 size_t Model::get_subpopulation_combined(TimePoint t, InfectionState s) const
 {
-    return std::accumulate(m_locations.begin(), m_locations.end(), (size_t)0,
-                           [t, s, this](size_t running_sum, const Location& loc) {
-                               return running_sum + get_subpopulation(loc.get_id(), t, s);
-                           });
+    // a single pass over all Persons, instead of calling get_subpopulation for every Location
+    return std::count_if(m_persons.begin(), m_persons.end(), [&](auto&& p) {
+        return p.get_location_model_id() == m_id && p.get_infection_state(t) == s;
+    });
 }
 
 size_t Model::get_subpopulation_combined_per_location_type(TimePoint t, InfectionState s, LocationType type) const
 {
-    return std::accumulate(
-        m_locations.begin(), m_locations.end(), (size_t)0, [t, s, type, this](size_t running_sum, const Location& loc) {
-            return loc.get_type() == type ? running_sum + get_subpopulation(loc.get_id(), t, s) : running_sum;
-        });
+    // a single pass over all Persons, instead of calling get_subpopulation for every Location
+    return std::count_if(m_persons.begin(), m_persons.end(), [&](auto&& p) {
+        return p.get_location_model_id() == m_id && p.get_location_type() == type && p.get_infection_state(t) == s;
+    });
 }
 
 TripList& Model::get_trip_list()
diff --git a/cpp/models/abm/model.h b/cpp/models/abm/model.h
index ee9077932f..0feeb02879 100644
--- a/cpp/models/abm/model.h
+++ b/cpp/models/abm/model.h
@@ -394,6 +394,8 @@ class Model
 
     /**
      * @brief Get the number of Person%s of a particular #InfectionState for all Cell%s.
+     * Note that this iterates over all Person%s of the Model. To count the Person%s of many Location%s or
+     * #InfectionState%s, do not call this in a loop, but count them in a single pass over get_persons() instead.
      * @param[in] location A LocationId from the Model.
      * @param[in] t TimePoint of querry.
      * @param[in] state #InfectionState of interest.
diff --git a/cpp/tests/test_abm_model.cpp b/cpp/tests/test_abm_model.cpp
index fe7926ff06..6522f78f56 100644
--- a/cpp/tests/test_abm_model.cpp
+++ b/cpp/tests/test_abm_model.cpp
@@ -178,6 +178,14 @@ TEST_F(TestModel, getSubpopulationCombined)
               2);
     // Verify the total count of persons with no symptoms across all locations.
     EXPECT_EQ(model.get_subpopulation_combined(t, mio::abm::InfectionState::InfectedNoSymptoms), 3);
+
+    // A person currently located in another model (e.g. in a graph ABM) is not counted.
+    auto visitor = add_test_person(model, school1, age_group_15_to_34, mio::abm::InfectionState::InfectedNoSymptoms);
+    model.get_person(visitor).set_location(mio::abm::LocationType::School, school1, model.get_id() + 1);
+    EXPECT_EQ(model.get_subpopulation_combined_per_location_type(t, mio::abm::InfectionState::InfectedNoSymptoms,
+                                                                 mio::abm::LocationType::School),
+              2);
+    EXPECT_EQ(model.get_subpopulation_combined(t, mio::abm::InfectionState::InfectedNoSymptoms), 3);
 }
 
 /**