OBJECTIVETo describe the influenza viruses antibody levels and contact patterns of individuals in rural and urban regions of Guangzhou and to understand how contact patterns and other factors would correlate with the levels on the titers of antibody.

METHODS"Google Map" was used to randomly select the study points from the administrative areas in Guangzhou region. Each participant was required to provide 5 ml blood serum sample to be tested against different strains of H1N1 and H3N2 influenza viruses.

RESULTS1) Using "Google map", 50 study points were selected but only 40 study points would meet the inclusion criteria. The cohort of this study consisted 856 households with 2 801 individuals. 1 821 participants (65% of the total number individuals in the cohort) completed the questionnaires. Among the 1 821 participants, 77.3% (1 407/1 821) and 22.7% (414/1 821) of them were from rural and urban areas respectively. There were more male participants in the rural but more female participants in the urban regions. Majority of the participants were from age group 18-59 followed by group 60 with aged 2-17 the least, in both rural and urban areas. 2) 78.1% (1 423/1 821) of the participants provided their serum samples. There appeared a strong correlation between age of the participants and the strength of their antibodies against that strain when a strain first circulated. In particular, seroprevalence was the highest at the age group 2-17. 3) 'Contact' was defined as persons having physical touch or/and conversation within one meter with the participants. Participants reported all having had large number of contacts. The proportion of participants having contacts with ten persons or above was the highest, ranging from 49.8% to 72.6%, particularly in age group 6-17. Compared to weekdays, participants had fewer contact persons on weekends.

CONCLUSIONThere was a strong correlation between the age of participants at the time when the strains first circulated and the seroprevalence against influenza virus strains of H1N1 and H3N2. Also, age of the participants and the frequencies of their contacts to people, was also correlated.

Adolescent ; Adult ; Antibodies, Viral ; blood ; Child ; Child, Preschool ; China ; epidemiology ; Contact Tracing ; Female ; Humans ; Influenza A Virus, H1N1 Subtype ; immunology ; Influenza A Virus, H3N2 Subtype ; immunology ; Influenza, Human ; epidemiology ; Male ; Middle Aged ; Seroepidemiologic Studies ; Young Adult