key: cord-007050-ibmr5bev
authors: Xu, Wei; Lu, Lu; Shen, Bo; Li, Jun; Xu, Jianqing; Jiang, Shibo
title: Serological Investigation of Subclinical Influenza A(H7H9) Infection Among Healthcare and Non–Healthcare Workers in Zhejiang Province, China
date: 2013-09-15
journal: Clin Infect Dis
DOI: 10.1093/cid/cit396
sha: 
doc_id: 7050
cord_uid: ibmr5bev

nan

infection with avian influenza A(H7N9) virus, including 37 deaths [1] . Zhejiang Province is the most affected area, where 46 cases were reported.

Poultry workers are at the highest risk for A(H7N9) infection in China [2] [3] [4] . However, the retrospective serologic study provided no evidence for A(H7N9) infection in poultry workers before November 2012 in eastern China [5] . Another high-risk population is the healthcare workers who may have close contacts with patients with symptomatic or asymptomatic A(H7N9) infection. A number of healthcare workers were infected, through contacts with patients, by Middle East respiratory syndrome coronavirus (MERS-CoV), a novel human coronavirus causing outbreaks of severe acute respiratory syndrome (SARS)-like illness in Middle East and Europe, although there is no confirmed evidence of efficient human-to-human transmission of MERS-CoV, like SARS-CoV [6] .

Here, we investigated the possible subclinical or asymptomatic infection with A(H7N9) virus among the healthcare workers in Zhejiang Province during the outbreak of A(H7N9) in 2013 by detecting the prevalence of anti-H7N9 antibodies in the leftover serum samples from 126 healthy healthcare workers and 615 healthy non-healthcare workers (as controls) in the cities of Taizhou, Hangzhou, and Shaoxing in Zhejiang Province, who underwent regular physical examinations between 1 April 2013 and 1 May 2013. A hemagglutination inhibition (HI) assay using guinea pig red cells and pseudoviruses expressing hemagglutinin of a representative A(H7N9) strain (A/Hangzhou/ 1/2013) was conducted for determining the HI titers of the serum samples, as previously described [7] .

We found that none of the serum samples from the healthcare and nonhealthcare workers contained H7-specific antibodies with HI titers of ≥20, whereas the HI titer of the serum sample from a patient with laboratory-confirmed A (H7N9) infection was ≥40. HI titers of 10 were detected in 3 of 123 serum samples (2.4%) from healthcare workers and 9 of 585 serum samples (1.5%) from the nonhealthcare workers. However, there was no significant difference between these 2 groups (Table 1 ). No significant difference was observed between the male and female groups and among different age groups in who had HI titer ≥10 ( Table 1 ).

The results suggest that none of our tested healthcare and non-healthcare workers in Zhejiang Province may have subclinical or asymptomatic A(H7N9) infection, because none of the serum samples contains H7-specific antibodies with HI titer ≥20. These results also implied that A(H7N9) might not be able to cause asymptomatic or subclinical infection. To the best of our knowledge, no case of asymptomatic A(H7N9) infections have been reported so far. This also suggests that people may be unable to acquire H7N9-specific immunity through asymptomatic or subclinical A(H7N9) infection, which may explain why people lack population immunity against A (H7N9) viruses. However, more extensive serological investigation on the asymptomatic or subclinical A(H7N9) infection among different high-risk groups at different regions should be performed. A serum sample with a hemagglutination inhibition (HI) titer of ≥40 from a patient with influenza A(H7N9) infection admitted to the Shanghai Public Health Clinical Center (SHAPHC) was included as a control in the HI assay. The study was reviewed and proved by the ethics committee of SHAPHC, and written informed consent was provided to the participants.

Human infection with avian influenza A(H7N9) virus in China: update

Human infection with a novel avian-origin influenza A (H7N9) virus

Origin and diversity of novel H7N9 avian influenza viruses causing human infection

Human infections with the emerging avian influenza A H7N9 virus from wet market poultry: clinical analysis and characterisation of viral genome

Serologic study for influenza A (H7N9) among high-risk groups in China

Novel coronavirus infection-update (Middle East respiratory syndrome-coronavirus)

Receptor specificity and erythrocyte binding preferences of avian influenza viruses isolated from India

contributed equally to this work. Correspondence: Shibo Jiang, MD, PhD, Shanghai Medical College, Fudan University, 130 Dong An Road

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