diff --git a/README.md b/README.md
index fb3abe0..efb97ad 100644
--- a/README.md
+++ b/README.md
@@ -55,16 +55,10 @@ filter:
 
 This build starts by pulling sequences from our live [fauna][] database (a
 RethinkDB instance).  For data privacy and security reasons, you'll need to
-provide credentials to the database yourself, using a `config_local.yaml`
-snippet like so:
-
-```yaml
----
-credentials:
-  rethink:
-    host: ...
-    auth_key: ...
-```
+provide credentials to the database yourself using two files in the `envdir/`
+directory: `envdir/RETHINK_HOST` and `envdir/RETHINK_AUTH_KEY`.  Each file
+should contain the appropriate value on a single line.  These files are ignored
+by git, so you can't (and shouldn't) commit them.
 
 If you don't have access to our database, you can run the build using the
 example data provided in this repository.  Before running the build, copy the
diff --git a/Snakefile b/Snakefile
index 33c41b4..bd59891 100644
--- a/Snakefile
+++ b/Snakefile
@@ -23,6 +23,11 @@ def field_map(fields):
     ]
 
 
+# Environment variables
+import envdir
+envdir.open()
+
+
 # Config
 configfile: "config.yaml"
 
@@ -46,14 +51,9 @@ rule download:
         build / "data/zika.fasta"
     params:
         fields = [ f[0] for f in fasta_fields ],
-
-        rethink_host     = config["credentials"]["rethink"]["host"],
-        rethink_auth_key = config["credentials"]["rethink"]["auth_key"],
     shell:
         """
         env PYTHONPATH=../fauna \
-            RETHINK_HOST={params.rethink_host:q} \
-            RETHINK_AUTH_KEY={params.rethink_auth_key:q} \
                 python2 ../fauna/vdb/download.py \
                     --database vdb \
                     --virus zika \
diff --git a/config.yaml b/config.yaml
index b01d808..a73a17e 100644
--- a/config.yaml
+++ b/config.yaml
@@ -7,14 +7,6 @@
 # feature definitions to analyze for amino acid changes.
 reference: config/zika_outgroup.gb
 
-# Credentials for pulling data from fauna/rethink.  These are not provided here
-# for data privacy and security reasons.  Please provide them in your
-# config_local.yaml file.
-credentials:
-  rethink:
-    host: ""
-    auth_key: ""
-
 # This defines the fields in the pipe-delimited FASTA header of each sequence.
 # It is used both for downloading from fauna and processing in augur.  Fields
 # may be mapped from one name in fauna to another in augur using "- from: to".
diff --git a/envdir/.gitignore b/envdir/.gitignore
new file mode 100644
index 0000000..31522f3
--- /dev/null
+++ b/envdir/.gitignore
@@ -0,0 +1,5 @@
+# This file serves to ignore required-but-sensitive environment variables as
+# well as to preserve the containing empty directory in the git repo.
+
+/RETHINK_AUTH_KEY
+/RETHINK_HOST