Volume 31, Supplement—May 2025
SUPPLEMENT ISSUE
Supplement
Nationwide Implementation of HIV Molecular Cluster Detection by Centers for Disease Control and Prevention and State and Local Health Departments, United States
, Camden J. Hallmark1, Nivedha Panneer, Rachael Billock, Olivia O. Russell, Mary Plaster, Jessica Alberti, Fathima Nuthan, Neeraja Saduvala, David Philpott, M. Cheryl Bañez Ocfemia, Scott Cope, Angela L. Hernandez, Sergei L. Kosakovsky Pond, Joel O. Wertheim, Steven Weaver, Saja Khader, Kevin Johnson, and Alexandra M. Oster
Table 2
Number of HIV molecular clusters detected each year through nationwide analysis of National HIV Surveillance System data by Centers for Disease Control and Prevention, United States, 2018-2023*
| Characteristics | 2018 | 2019 | 2020† | 2021 | 2022 | 2023 | Total no. |
|---|---|---|---|---|---|---|---|
| National priority clusters detected‡ |
69 |
74 |
48 |
61 |
77 |
75 |
404 |
| Clusters meeting national priority criteria as of December 2023‡ |
2 (3) |
8 (11) |
5 (10) |
9 (15) |
10 (13) |
40 (53) |
74 (18) |
| Median cluster size when first detected (range) |
7 (3–24) |
8 (3–19) |
8 (3–16) |
7 (4–18) |
7 (3–14) |
7 (3–23) |
7 (3–24)§ |
| Median cluster size as of December 2023 (range) |
17 (3–193) |
17.5 (3–90) |
20 (3–49) |
16 (6–72) |
11 (3–47) |
9 (3–26) |
13 (3–193)§ |
| Clusters involving >1 jurisdiction as of December 2023 |
58 (84) |
62 (84) |
43 (90) |
51 (84) |
56 (73) |
55 (73) |
325 (80) |
| Clusters with no primary jurisdiction at detection |
6 (9) |
9 (12) |
4 (8) |
5 (8) |
5 (6) |
6 (8) |
35 (9) |
| Jurisdictions with >1 cluster as the primary jurisdiction at detection¶ |
25 |
25 |
25 |
20 |
26 |
28 |
43# |
| Jurisdictions with >1 cluster with substantial involvement** |
NA |
NA |
NA |
NA |
27 |
31 |
NA |
| Clusters with no jurisdiction ever substantially involved |
NA |
NA |
NA |
NA |
2 (3) |
5 (7) |
NA |
| Clusters with only 1 jurisdiction ever substantially involved |
NA |
NA |
NA |
NA |
68 (88) |
67(89) |
NA |
| Clusters with >2 jurisdictions ever substantially involved | NA | NA | NA | NA | 7 (9) | 3 (4) | NA |
*Values are no. (%) except as indicated. NA, not applicable. †National cluster detection was not conducted for the March 2020 quarter because of disruptions related to the COVID-19 pandemic. ‡National priority clusters are defined as clusters at the 0.5% genetic distance threshold with >5 diagnoses in the previous 12 months or >3 diagnoses in the previous 12 months in low-burden jurisdictions (those having <200 reported HIV diagnoses annually). National priority criteria is assessed on an ongoing basis. §Overall median and range. ¶Primary jurisdiction is defined as the jurisdiction in which >50% of cluster members resided at the time of HIV diagnosis. If there is no single jurisdiction in which >50% of cluster members reside at diagnosis, no primary jurisdiction is assigned. #Total number of unique jurisdictions. **Substantial involvement in national priority clusters is defined as >3 diagnoses in a given jurisdiction (resident at diagnosis or current resident) in the previous 12 months. Multiple jurisdictions can be substantially involved in a cluster at the same time.
1These first authors contributed equally to this article.