Seroprevalence of Anti-H5 Antibody among Thai Health Care Workers after Exposure to Avian Influenza (H5N1) in a Tertiary Care Center

Abstract

After the initial atypical presentation of a patient with avian influenza (H5N1) infection, paired acute-phase and convalescent-phase serum samples obtained from 25 health care workers (HCWs) who were exposed to the patient were compared with paired serum samples obtained from 24 HCWs who worked at different units in the same hospital and were not exposed to the patient. There was no serologic evidence of anti-H5 antibody reactivity or subclinical infection in either of the groups.

Two clustered cases of confirmed influenza A(H5N1) virus infection, Cambodia, 2011

“…Transmission of A(H5N1) virus from patients to HCW or other close contacts, and asymptomatic or subclinical A(H5N1) virus infections are rare but have occurred in the past [32][33][34][35]. Despite the presence of symptoms during travel and during home as well as hospital care, there was no clinical or laboratory evidence of person-to-person transmission from Case 1 or Case 2 to neighbours, family members or unprotected HCW.…”

Detection by microneutralization of antibodies against avian influenza virus in an endemic avian influenza region

“…These data, along with the reports of other investigators from Southeast Asia, suggest that transmission of H5N1 from poultry to humans may have a broad, if not protean, clinical spectrum of illness as measured by the seroprevalence of anti-H5 antibodies. In regions endemic for poultry infection, low anti-H5 micro-NT titres (<1 : 80) have been detected in up to 3% of study participants [4][5][6]. In one population-based study from Vietnam, a dose-response relationship was noted between poultry exposure and flu-like illness among persons who had healthy poultry in the household, those with sick or dead poultry in the household, and those who had direct contact with sick poultry [9].…”

“…Haemagglutination inhibition tests for the KAN-1 and PT strains were performed in all cases with positive low-titre anti-H5 micro-NT, to detect cross-reactivity with circulating antibodies after prior human influenza virus infection. The WHO defines a positive test result as an anti-H5 micro-NT titre of >1 : 80 with a confirmatory western blot [1,4,5,8].…”

“…Studies of H5N1 infection among Thai patients, healthcare workers and poultry farmers have found that up to 3% of persons screened with a microneutralization assay have low titres of antibodies against avian influenza virus (anti-H5 micro-NT) [4][5][6]. Current disease understanding suggests that detection of anti-H5 micro-NT titres of <1 : 80 is a false-positive result [1].…”

A Nationally Coordinated Laboratory System for Human Avian Influenza A (H5N1) in Thailand: Program Design, Analysis, and Evaluation

“…Although human-to-human transmission of avian influenz A (H5N1) has not yet been efficient the theoretical risk exists and is compounded by recent isolation of a strain with potential for human-tohuman transmission [3][4][5]. Key preparedness strategies include designated interdisciplinary planning committees, committee liaisons to external health entities, linkages with regional emergency preparedness groups, written pandemic influenz protocols, and plans for facility access, occupational health, mass distributions of vaccine and antiviral agents, and surge capacity.…”