The bacteria nobody can identify get sent to Atlanta

National Shigella surveillance is passive: it counts
laboratory-confirmed human infections as they are reported, rather than going
looking for cases. What makes it work is a chain of laboratories, each passing
on what it cannot resolve.

How an isolate travels

1. Clinical diagnostic laboratories submit Shigella isolates to **state
   and territorial public health laboratories**.
2. There they are confirmed, speciated and subtyped.
3. Unusual or untypable isolates are forwarded to the CDC — and **the
   results are reported back to the public health laboratories.**

That last clause is the part that keeps the system working. A state laboratory
that sends away everything it cannot identify and hears nothing back learns
nothing, and stops sending. Returning the answer is what turns a collection
process into a capability-building one.

Where the data goes

State and territorial public health laboratories report electronically to the
CDC through a variety of mechanisms, and the data collects in the
Laboratory-Based Enteric Disease Surveillance (LEDS) system.

**The annual summaries of this data are the national source of species and
subtype information for Shigella.** Not just how many infections — which
species, and which subtype, which is what distinguishes an ordinary year from
a resistant strain spreading.

Annual summaries for 2007–2016 are archived on CDC Stacks, with separate
tables for the 2007–2009 reports and appendices for the 2010–2012 ones — worth
knowing, because the data for those years is not all in the main documents.

Source: Centers for Disease Control and Prevention.