TITLE: Field sampling for drinking water
AUTHORS: Sneha Shrestha, Christopher LeBoa

[DESCRIPTION]
The method we used for sampling drinking water for households when detecting S. Typhi and Paratyphi in Nepal 

[GUIDELINES]
Sterility during water sample collection
1. Sterility of collected water sample: The primary risk of sample cross-contamination comes 
from either the field assistant or water/DNA from another household. 
a. Field assistant: It is important that the field assistant, whom comes into contact with 
water at multiple households, uses proper technique and does not contaminate the 
water being collected by touching or handling the opening or inside of the bag. 
b. Collection instrument: while the inside of each WhirlPak is sterile, the outside is not. 
Thus, a Whirlpak cannot be directly dipped into a water tank to collect water since it 
is not sterile, has been handled by the field assistant and may have come into 
contact with another household’s water during transport. Items owned and used by 
the household are an exception. Since water at the household level is routinely 
transferred via multiple non-sterile methods (pipes, valves, jugs, cups, etc) prior to 
consumption, it is ok, for water to be in contact with these devices prior to collection. 
2. Contamination of household water: It is similarly important that potential pathogens are not 
introduced into a water supply when we collect from there.

Definitions: 
Origination of water: Defined as the principal, original source of water. For water that is 
processed or distributed (i.e. municipal or private water company) then the initial water 
treatment and distribution plant is the origination point. For unprocessed water (i.e. 
collected or distributed directly from ground water or surface water for consumption), 
then the source of water prior to distribution or collection is the origination (i.e. river or 
groundwater).
Freshness: Refers to time since water is delivered from the origination source. For 
instance, the freshest possible water would be immediately collected from a pipe that 
has actively running water from a municipal water source. Water that has been stored 
and has been stagnant/still for an amount of time, freshness decreases. Thus, water 
collected from a running pipe and stored for 24 hours would be less fresh then running 
pipe water but fresher then water collected and stored 1 week prior. 
End-user treatment: Any treatment of water done at the household level prior to use or 
consumption, including but not limited to filtration, boiling or chemical treatment such as 
chlorination.

[STEPS]
1. All water will be collected at the point closest to the origination of that water supply prior to end-user treatment to minimize the time for S. Typhi or Paratyphi DNA to degrade in 
water, if present. If the only option is to sample from water that has been stored, choose the 
freshest (most recently stored) source.
SECTION: Sample Collection
2. Pre-label all Whirl-Pak bags with a fill line representing 1 litre of water 
a. Fill a bag with exactly 1 litre of water in the lab. Mark the outside of the bag with a 
line where the water reaches. Copy this line to the rest of the Whirl-Pak bags.
SECTION: Sample Collection
3. Place two duplicate random number stickers on the Whirl-Pak bag.
SECTION: Sample Collection
4. Put on gloves and ipen the bag, taking care not to touch the inside of the bag
SECTION: Sample Collection
5. Fill the bag with 1 liter or water
SECTION: Sample Collection
6. Close the bag with the pipe-locking device
SECTION: Sample Collection
7. Remove gloves
SECTION: Sample Collection
8. Scan the sample barcode into RedCap
SECTION: Sample Collection
9. If the code does not scan, manually enter it
SECTION: Sample Collection
10. Take a picture of the sample in the RedCap app, making sure that you can see the 
barcode number
SECTION: Sample transport
11. Place the full bag Whirl-Pak in an upright plastic bottle inside the cooler bag/backpack
                                                                                                                                                                                                                                                                                                                                                                                                                    
SECTION: Sample transport
11.1. Unused Whirl-Pak bags should be kept in a separate compartment from water 
samples
SECTION: Sample transport
12. Minimize opening and closing the cooler to maintain temperature control.
SECTION: Sample transport
13. If maintaining temperature control is a challenge, consider placing temperature loggers 
inside each cooler bag.
SECTION: Sample Collection
5.1. If necessary, ask the household member to turn on the water spigot so that you do not contaminate your gloves.
SECTION: Sample Collection
5.2. If the household uses water from a communal spigot, collect from this point 
i. If a hose is connected to a communal spigot, remove it to collect directly from the tap

SECTION: Sample Collection
5.3. If the community spigot is not functioning/the water is not running, sample water  from the house or building collection tank, using the sterile hand pump
SECTION: Sample Collection
5.4.  If the storage tank in inaccessible, you can sample from stored water in a jug 
i. Choose the freshest source of stored water (the one that was stored the most recently) ii.Avoid using a cup or container to transfer water from the jug If the container is too heavy to lift and pour into the Whirl-Pak bag, you can request to use the same cup or device the household uses to transfer water.