Lab Matters Fall 2023 | Page 89

APHL 2023 POSTER ABSTRACTS

Evidence of Mpox Virus Infection from Non-Lesion Specimens Among Persons Without Characteristic Lesions or Rash — District of Columbia , August 2022

N . Baird 1 , Y . Ogale 1 , M . Townsend 1 , I . Berry 1 , A . Mangla 2 , M . Lee 2 , C . Willut 2 , P . Ashley 2 , T . Rhodes 2 , T . Notigan 1 , N . Wynn 1 , C . Kling 1 , T . Smith 1 , L . Priyamvada 1 , W . Carson 1 ; 1 US Centers for Disease Control and Prevention , 2 District of Columbia Department of Health

Since May 2022 , mpox infections have been confirmed in nonendemic countries worldwide . Classic signs and symptoms of mpox infection include a prodromal period of influenza-like symptoms that generally start within three weeks of exposure to the virus , with a rash appearing approximately 1 – 3 days after fever onset . During the 2022 multinational mpox outbreak , a significant number of patients reported rash as their first symptom , in the absence of a prodrome . Diagnosis is by real-time PCR , after rash onset , with lesion material being the most accurate specimen type for testing . Mpox virus has been detected in non-lesion specimens from persons experiencing signs and / or symptoms of mpox infection , but evidence supporting the utility of non-lesion specimens for detection of mpox infection is limited . Transmissibility data from non-lesion sites with detectable mpox virus are also lacking . Over a three-week period in August 2022 , various specimen types were collected from persons without characteristic mpox rash presenting for their first dose of Jynneos vaccine at two DC Health clinics to identify previously undiagnosed mpox infection . Participants ( n = 543 ) provided blood , pharyngeal swab and rectal swab specimens ; PCR was used to determine the presence of mpox virus in these specimens . PCR-positive specimens were cultured and mpox virus titers were determined for viable specimens . Serum specimens were tested for anti-orthopoxvirus IgG antibodies , with a subset tested for IgM antibodies . Of 543 participants providing ≥1 specimen , three individuals had a specimen with detectable mpox virus DNA by real-time PCR : one pharyngeal ( 1 / 522 , 0.2 %) and two rectal ( 2 / 164 , 1.2 %) specimens . Only the two rectal specimens were culture positive , with titers of 2.9 x 10^7 pfu / mL and 1.5 x 10^5 pfu / mL . The three participants with PCR-positive specimens were IgG negative ; however , two of the three participants were IgM positive , indicating a recent infection . Two of the three participants with mpox-positive specimens reported having no symptoms , while the third participant reported only fever and headache with no other symptoms . These results demonstrate that individuals may have detectable mpox virus before the recognition of , or in the absence of , characteristic mpox lesions and may be capable of viral shedding , as evidenced by the high-titer values in the rectal specimens . While the mpox virus infectious dose for humans is unclear , animal study data suggest that the high titers like those observed from the two rectal specimens may be sufficient for human-human transmission . Although data on alternative nonlesion specimen types is informative , the low number of infections detected in the absence of rash suggests that screening efforts using these specimen types may have limited effectiveness in reducing transmission and controlling future outbreaks .

Presenter : David Lowe , nqu9 @ cdc . gov

Identification of Tecovirimat Resistance-associated Mutations in Human Mpox Virus , Los Angeles County

J . Garrigues , P . Hemarajata , A . Karan , M . Kim , N . Green ; Los Angeles County Public Health Laboratory

Tecovirimat ( also known as TPOXX or ST-246 ) is a drug available for treatment of mpox through the FDA ’ s Expanded Access program . Previous studies identified more than 20 mutations in VP37 , a conserved orthopoxvirus envelope protein required for extracellular virus particle generation , that are associated with tecovirimat resistance . In Los Angeles County , epidemiologic surveillance of mpox cases based on review of medical history including immunecompromising conditions such as HIV infection , severe disease including hospitalization , and disease that did not improve after tecovirimat treatment identified nine cases with suspected resistance , including two patients who succumbed to infection and expired . To further investigate the possibility of tecovirimat resistance in these cases , a laboratory surveillance network was established whereby clinical and commercial laboratories provided specimens for whole-genome sequencing of mpox virus ( MPXV ) to the Los Angeles County Public Health Laboratory ( LACPHL ). Specimens obtained from these individuals harbored a total of seven different tecovirimat resistance-associated mutations in VP37 ( H238Q , N267D , A288P , A290V , D294V , A295E , and I372N ), as well as six additional mutations previously unassociated with resistance ( T220A / I , P243S , T245I , A265D , and T289A ). Allele frequency analysis showed some patients displayed resistance mutation heterogeneity within single lesion specimens , and different mutations were identified among distinct lesion specimens collected from the same patient , suggesting these mutations were selected or acquired over the course of treatment and not present when infection occurred . Importantly , phenotypic testing confirmed tecovirimat resistance in a subset of specimens , demonstrating that these mutations indeed result in resistance . Taken together , these findings confirm a low barrier for tecovirimat resistance and underscore the need for additional therapeutics when treating mpox in certain patients . Clinical management needs to ensure optimization of drug delivery / dosing as well as immune function when treating with tecovirimat to prevent resistance . LACPHL is working to validate MPXV sequencing for identification of mutations associated with tecovirimat resistance to be used as a diagnostic tool .

Presenter : Nicole Green , nicgreen @ ph . lacounty . gov

Lessons from Lesions : Trends in Specimen Submissions and Test Performance During the 2022 Mpox Outbreak in New York City

E . Kopping 1 , 2 , V . Ruiz 2 , M . Leelawong 2 , I . Krane 2 , R . Fowler 2 , S . Hughes 2 ; 1 US Centers for Disease Control and Prevention , 2 New York City Department of Health and Mental Hygiene Public Health Laboratory

Background : New York City ( NYC ) was an early epicenter in the 2022 mpox outbreak . The NYC Public Health Laboratory ( NYC PHL ), a Laboratory Response Network ( LRN ) lab , was initially NYC ’ s sole testing facility . NYC PHL tested thousands of specimens using the United States Food and Drug Administration-cleared Non-Variola Orthopoxvirus ( NVO ) real-time PCR assay distributed by the LRN . We