Phase I	Field Sampling	1. Check macrofoam swab kits (e.g., expiration date, tube leakages, and swab wetness)
2. Swab surface (limit surface area to ≤100 inch2 (645 cm2))
3. Place swabs into the transport tubes, and tighten the caps securely to prevent leaking during shipping
4. Place swab kit in a ziplock-bag
Phase II	Sample transport and storage	1. Sampled swabs should be stored -70 °C (or -20 °C)
2. Transporting swab samples to laboratory at 0-4 °C (cold-packs) in an insulated container and ship within 48 hr of collecting swabs
Phase III	RNA etraction	1. Check lysis buffer (e.g., expiration data)
2. Add MS2 as an internal control into lysis buffer before adding 100% ethanol
RNA purification and concentration	3. Clean lab bench and small equipment using RNA RNase removal solution
4. Change gloves frequently during steps to avoid a RNA cross-contamination
Phase IV	RT-PCR Assay (QA/QC)	1. Include quantified norovirus transcript RNAs (GI and GII) for each RT-qPCR assay to control for variations in Ct values for each PCR run
2. Use absence of MS2 signal to monitor presence of PCR inhibitors