Vector Index

The vector index is the relative abundance of infected mosquitoes and is a way to quickly estimate the risk of arbovirus transmission in an area.

Fields

  • Agency: Choose the agency or agencies for which you wish to calculate a vector index. Multiple agencies can be selected by using the CTRL/CMD/SHIFT keys while selecting values. This could be your own agency to compare the current year to past years, or more than one agency to compare to neighboring districts. If the Treat each selected agency independently box is checked, the vector index will be stratified by agency (ignored if only one agency is selected). If left unchecked, it will be aggregated for all selected agencies.
  • Year: This is the year for which you wish to calculate a vector index. When calculating the abundance anomaly component, this year’s abundance at the desired time interval will be compared to the average abundance from the previous 5 years.
  • Time Interval: How frequently should the vector index components be calculated? There are several built-in options, or you can manually specify a date range within the selected year. Date format is based on the settings under Account Preferences.
  • Spatial Filter: This feature allows you to filter results within the agency or agencies. You can draw a polygon on the map using the feature tab, or include a previously saved feature from the Spatial Features page. Polygon example Alternatively, you can filter by site group, region (determined when creating a new site), or specific site. For these filters, multiple values can be selected by using the CTRL/CMD/SHIFT keys while selecting values. If the Treat each selected filter independently box is checked, the vector index will be stratified by spatial filter, otherwise it will be aggregated for the selection. If the “All Available…” option is selected or no feature polygon(s) is provided, any calculation(s) will not use spatial filters.
  • Target/Virus: The pathogen for which you wish to estimate the pool infection rate component.
  • Species: Here you can choose whether to look at the vector index for all species or selected species of interest. Multiple species can be selected by using the CTRL/CMD/SHIFT keys while selecting values. If the Treat each selected species independently box is checked, the vector index will be stratified by species, otherwise it will be aggregated for all selected species.
  • Sex/Condition: Typically, females of various conditions are of interest when calculating the vector index, but you could also examine males, unknown sex, eggs, larvae, and pupae. Multiple values can be selected by using the CTRL/CMD/SHIFT keys while selecting values, and checking the Treat each selected sex/condition individually box will stratify the vector index by the selected values.
  • Trap Type: Filter the results by the trap type used for the collection. This is helpful to ensure that results are comparable over time and/or across agencies. Similar to Sex/Condition, multiple trap types can be selected by using the CTRL/CMD/SHIFT keys while selecting values, and checking the Treat each selected trap type individually box will stratify the vector index by the selected traps.
  • Trap Night Restrictions: You can further restrict the collections used to calculate the vector index by the number of trap nights a trap was set for.
  • Point Estimate: The type of infection rate to calculate for the pool infection rate component. The bias-corrected MLE will be appropriate for most situations, but you can also choose to calculate the MLE or MIR.

Results

The # of Calculations indicator shows how many calculations will be performed based on the stratifications (checkboxes) that have been selected. If none of the boxes were checked, the vector index at the desired time interval will be aggregated to a single calculation. The resulting table showing the vector abundance for the selected year and the previous 5 years is downloadable. You also have the option to view a time series graph comparing the vector index at the selected time interval.