Rails Ajax Refresh Partial while persisting params

I have a Rails app with a controller/view called "calls". Here is the basic controller action for index:

calls_controller.rb

def index
    if params[:region].present?
      @assigned = Call.where(region_id: params[:region][:area]).assigned_calls.until_end_of_day
      @unassigned = Call.where(region_id: params[:region][:area]).unassigned_calls.until_end_of_day
   else
     @assigned = Call.assigned_calls.until_end_of_day
     @unassigned = Call.unassigned_calls.until_end_of_day
   end
  end

Here are my views:

index.js.erb

$('#active').html("<%= escape_javascript render :partial => 'calls/assigned_calls', :locals => {:assigned_calls => @assigned} %>");
$('#inactive').html("<%= escape_javascript render :partial => 'calls/unassigned_calls', :locals => {:unassigned_calls => @unassigned} %>"); 

$(".select").select2({
        placeholder: "Select One",
        allowClear: true
  });

index.html.erb

<div id="active">
  <%= render "assigned_calls" %>
</div>

<div id="inactive">
  <%= render "unassigned_calls" %>
</div>


<script>
$(document).ready(function() {
    setInterval(function () {
            $.ajax('calls/<%= params[:region][:area] %>');
    } , 5000);
});
</script>

_assigned_calls.html.erb (view code omitted)

<%= form_tag calls_path, :method => 'get' do %>
  <p>
<%= select_tag "region[area]", options_from_collection_for_select(Region.order(:area), :id, :area, selected: params[:region].try(:[], :area)), prompt: "Choose Region" %>
<%= submit_tag "Select", :name => nil, :class => 'btn' %>

So what's happening is on page load if I do not have the params of :region passed it sets the calls without being scoped by region. If region_id is present then it scopes calls where region_id is "1" or whatever the Region ID is that is passed from the submit_tag.

This works fine in the controller and view, however here's my problem. My index.html.erb I need to refresh the partials WITHOUT disturbing the params passed. So on setInterval I need to figure out how to reload the partials while persisting the params passed in the URL.

I tried to figure this out using a setInterval method but I'm not sure what I'm doing here 100%.

Can someone give me some advice on how to refresh the partials every 5 seconds while persisting the params so my instance variables persist through refresh?

If you need more context and/or code please let me know.