diff --git a/Dockerfile b/Dockerfile
index 4510bcb..9c5eb59 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,10 +1,10 @@
-# Docker image for a tn93 development environment
-FROM oraclelinux:8
+# Docker image for a tn93 development environment (Red Hat Universal Base Image 8.10)
+FROM redhat/ubi8:8.10
 
 # Set up environment and install dependencies
 RUN yum -y update && \
-    yum install -y cmake gcc-c++ gcc-toolset-10 git make oracle-epel-release-el8 && \
-    echo 'source /opt/rh/gcc-toolset-10/enable' > ~/.bashrc && \
+    yum install -y cmake gcc-c++ gcc-toolset-12 git && \
+    echo 'source /opt/rh/gcc-toolset-12/enable' > ~/.bashrc && \
     source ~/.bashrc
 
 # To compile tn93 within the development environment:
diff --git a/scripts/intrahost_dists.py b/scripts/intrahost_dists.py
new file mode 100755
index 0000000..c12df4d
--- /dev/null
+++ b/scripts/intrahost_dists.py
@@ -0,0 +1,101 @@
+#! /usr/bin/env python3
+'''
+Calculate all pairwise distances between sequences from the same individual
+'''
+
+# imports
+from gzip import open as gopen
+from subprocess import check_output, DEVNULL, PIPE
+from sys import argv
+import argparse
+
+# constants
+TN93_BASE_COMMAND = [
+    'tn93',
+    '-l', '1', # at least 1 overlap
+]
+
+# parse user args
+def parse_args():
+    parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.ArgumentDefaultsHelpFormatter)
+    parser.add_argument('-i', '--input', required=False, type=str, default='stdin', help="Input FASTA")
+    parser.add_argument('-t', '--threshold', required=False, type=float, default=1., help="TN93 Distance Threshold")
+    parser.add_argument('-a', '--ambigs', required=False, type=str, default='resolve', help="TN93 Resolve Ambigs")
+    parser.add_argument('-g', '--ambig_fraction', required=False, type=float, default=1., help="TN93 Ambiguity Fraction")
+    parser.add_argument('-o', '--output', required=False, type=str, default='stdout', help="Output File")
+    args = parser.parse_args()
+    return args
+
+# load FASTA sequences from a file
+def load_fasta(fn):
+    # set up input file stream
+    if fn.strip().lower() == 'stdin':        # standard input
+        from sys import stdin as f
+    elif fn.strip().lower().endswith('.gz'): # gzip-compressed file
+        f = gopen(fn, 'rt')
+    else:                                    # uncompressed file
+        f = open(fn, 'r')
+
+    # parse FASTA
+    seqs = dict(); curr_ID = None; curr_seq = ''
+    for line in f:
+        l = line.strip()
+        if len(l) == 0: # skip empty lines
+            continue
+        if l[0] == '>': # header line
+            if len(curr_seq) != 0:
+                seqs[curr_ID] = curr_seq
+            curr_ID = l; curr_seq = ''
+        else:           # sequence line
+            curr_seq += l
+    if len(curr_seq) != 0:
+        seqs[curr_ID] = curr_seq
+    return seqs
+
+# return dictionary where seqs_per_person[person] = set of sequence IDs from `person`
+def load_seqs_per_person(seqs):
+    seqs_per_person = dict()
+    for k in seqs:
+        person = k.lstrip('>').split('|')[0].strip()
+        if person not in seqs_per_person:
+            seqs_per_person[person] = set()
+        seqs_per_person[person].add(k)
+    return seqs_per_person
+
+# calculate all pairwise distances between sequences from the same individual (this is the main logic of this script)
+# currently not parallelizing across people because tn93 parallelizes pairwise distance calculations,
+# but we could easily parallelize across people as well
+def calc_intrahost_dists(seqs, seqs_per_person, out_fn, tn93_t, tn93_a, tn93_g):
+    # open output file
+    if out_fn.strip().lower() == 'stdout':
+        from sys import stdout as output
+    elif out_fn.strip().lower().endswith('.gz'):
+        output = gopen(out_fn, 'wt')
+    else:
+        output = open(out_fn, 'w')
+
+    # build tn93 command
+    tn93_command = TN93_BASE_COMMAND    # start with base command
+    tn93_command += ['-t', str(tn93_t)] # add max distance threshold
+    tn93_command += ['-a', str(tn93_a)] # add ambig resolve
+    tn93_command += ['-g', str(tn93_g)] # add ambiguity fraction
+
+    # run on all people
+    for person_num, person in enumerate(seqs_per_person):
+        if len(seqs_per_person[person]) < 2:
+            continue # skip people with just 1 sequence
+        curr_fasta = '\n'.join('%s\n%s' % (k,seqs[k]) for k in seqs_per_person[person])
+        o = check_output(tn93_command, stderr=DEVNULL, input=curr_fasta, encoding='ascii')
+        if person_num == 0:
+            output.write(o.strip()); output.write('\n')
+        else:
+            for l in o.splitlines()[1:]:
+                output.write(l.strip()); output.write('\n')
+    output.close()
+
+# run tool
+if __name__ == "__main__":
+    args = parse_args()
+    seqs = load_fasta(args.input)
+    seqs_per_person = load_seqs_per_person(seqs)
+    calc_intrahost_dists(seqs, seqs_per_person, args.output, args.threshold, args.ambigs, args.ambig_fraction)