International Conference on Emerging Infectious Diseases

Published Jul 12, 2010

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http://www.cdc.gov/eid/content/16/7/ICEID2010.pdf

This conference held in Atlanta, Georgia covers other infectious diseases but not surprisingly, many of the research topics addressed influenza, mostly swine flu, but also bird flu. Truly, it must be fascinating to be able to attend such a gathering. I am envious. Scroll on thru the link to discover all of the studies being presented.

This particular study caught my eye. Did you know that asymptomatic cases can pass on infection? This speaks to the common sense of being vaccinated as an HCW. These workers may not have been infected on the job.There was plenty of swine flu in the communities where they lived.

Asymptomatic Infection of Influenza A(H1N1) 2009 Pandemic Virus among Japanese Healthcare Workers
Background: One of the limitations of the current influenza surveillance is the detection of asymptomatic cases, which play important role in disease transmission. It is difficult to detect asymptomatic cases even with sensitive molecular methods, and a retrospective serological test is the method to confirm. The asymptomatic infection among healthcare worker may the big issues in terms of infection control, but its occurrence is unknown. We conducted sero-epidemiology study to elucidate the prevalence of asymptomatic infection of influenza A(H1N1) pandemic virus in a cohort of healthcare workers in Japan. Methods: One hundred forty healthcare workers, including 25 pediatricians, in 18 private pediatric outpatient clinics in Sendai, Japan, have been participating in the cohort study to monitor the incidence of influenza infection during pandemic. Serum was collected between 38th and 42nd epidemiological week, the early stage of community transmission in Sendai. Hemagglutination inhibition (HI) test was used to measure the antibody against pandemic influenza. Purified hemagglutinin of A/California/07/2009 pdm was used as the antigen for HI test, and was kindly provided by National Institute for Infectious Disease in Tokyo, Japan. All participants were asked to fill the questionnaire on history of influenza-like illness from May 2009 to the day of sampling. Paired-serums of symptomatic
laboratory-confirmed cases in this cohort study were used as the reference for HI titer. Results: Among 123 participants, 33 (27%) had HI antibody titer below 1:10, 39 (32%) had 1:10, 16 (13%) had 1:20, 18 (15%) had 1:40, 11 (9%) had 1:80, 4 (3%) had 1:160, and 2 (1%) had 1:320. All laboratory-confirmed cases had HI titer higher than 1:160 in convalescence phase serum. Only one case reported to have influenza-like illness after May 2009 and most of them were asymptomatic. By stratification by the job title, medical doctors had highest attack rate.
Conclusion: We were able to confirm the high prevalence of infected cases, as well as asymptomatic cases, among healthcare workers in Japan despite of the fact that most of them wearing surgical or N95 masks. Alternative approach should be taken place in healthcare facilities to protect workers from influenza infection.

(hat tip Avian Flu Diary)