Southern Nevada Health DistrictMaternal TB Investigation – Interim Report #2December 23, 2013Authors:Kaci Hickox, MPH, MSN, RN – Nurse EpidemiologistNancy Williams, MD, MPH – Medical EpidemiologistJoseph P. Iser, MD, DrPH, MSc – Chief Health OfficerBackground Update(This is an update. Please refer to Brief Interim Report #1 for background information.)The Southern Nevada Health District TB Program and Office of Epidemiology have beenconducting a TB contact investigation related to the postmortem TB diagnosis in a Clark Countyresident (Patient A) who delivered premature twins (Patients B & C) two-months before herdeath in July, 2013. The twins remained in the NICU until their deaths (in June and August).Our goals in conducting this TB contact investigation follow the CDC’s prioritized strategies toprevent and control TB in the United States1:1. To promptly detect and report persons who have contracted TB; and2. To protect close contacts of patients with contagious TB from contracting TB infectionand disease, by identifying and treating people with active TB disease and identifying andoffering treatment to people with evidence of noninfectious Latent TB Infection (LTBI).Definitions• Latent TB infection (LTBI), also referred to as “TB infection,” is a condition in whichan individual is infected with the bacterium Mycobacterium tuberculosis, or other,closely related species of Mycobacterium, but does not currently have active disease.Even if infected, people without active disease are not infectious (i.e., they cannot spread
the disease). However, they are at risk for their infections progressing to tuberculosis
disease, thus LTBI treatment is recommended. Persons are diagnosed with LTBI when
they have positive tests for infection with M. tuberculosis (which can include a tuberculin
skin test (TST), Quantiferon-TB tests (QFT), or a T-SPOT test), but they are
asymptomatic and have negative chest radiographs.
• TB disease, also referred to as “active TB” or “active TB disease,” indicates that the
disease caused by M. tuberculosis is clinically active. Patients with TB disease generally
have symptoms of disease which can include, but are not limited to, unexplained weight
loss, fever, cough, night sweats, and shortness of breath. Chest radiograph or a positive
culture result for M. tuberculosis or a closely related species is an indication of TB
disease.
• Infectious TB disease refers to TB disease of the lungs or larynx; persons with infectious
TB have the potential to transmit M. tuberculosis to other persons.
Methods
Contact Investigation(s)
We identified, prioritized, and evaluated personal contacts of Patient A for TB (family, friends,
coworkers, church-goers, etc.) and supported evaluation of contacts in healthcare facilities
(inpatient and outpatient settings). As a proxy for determining the risk of exposure of other
NICU infants who had resided in the unit with the twins, we tested healthcare workers (HCWs)
in the neonatal intensive care unit (NICU). If no evidence of transmission to HCWs was found,
we believed that would reasonably indicate that no transmission to NICU infants had occurred,
as the HCWs would have had closer contact with Patients A–C than other NICU infants.
Because it can take 8–10 weeks for tests to reveal TB infection after someone has been exposed
to a person with infectious TB disease, contacts were retested ≥8 weeks of last contact with the
TB patients if the first test was performed <8 weeks of last contact.
After test results indicated that transmission to NICU staff members had occurred, we expanded
our plan to include the evaluation of infants who resided in the Level 3 NICU at times when
infectious persons could have been present. We also evaluated people who visited those infants
in the NICU. Evaluation of TB infection or disease is different for infants than for adults.3
Because TB tests can be inaccurate in infants, we consulted experts in pediatric TB, who
recommended that evaluations occur immediately (Round 1), at 6 months of age (adjusted for
prematurity when applicable; Round 2), and at 1 year of age (adjusted for prematurity; Round 3).
Tests are more accurate after 6 months of age. Depending on the age of the infant during the
initial evaluation up to three rounds of evaluations might be needed. Evaluation of an infant for
TB should include a TST, chest radiograph (chest x-ray), and physical examination.
A second TB contact investigation was initiated upon identifying that one of the NICU staff
members had developed active (infectious) TB disease. We identified contacts of the newly
identified TB case-patient from among hospitalized adult patients, hospitalized infant patients,
and co-workers (HCW). We prioritized their testing based on their exposure to the case-patient.
For the purposes of this report, results of testing for both investigations are combined.
Identifying Active TB Disease Case-Patients / Genotyping
Contacts with clinical, radiographic, or microbiologic evidence of TB disease were considered to
have active TB disease and appropriate treatment was initiated. Contacts with indications of
infectious TB disease resulted in initiation of new contact investigations to identify their contacts
during their infectious periods. When available, Mycobacterium isolates were further
characterized through genotyping, a technique used to analyze the genetic material (e.g., DNA)
การแปล กรุณารอสักครู่..
