Background: Since Taiwan has high population density and a similar ecological environment to Mainland China, the epi-center of influenza viruses, it is very important to establish influenza virologic surveillance systems in both animal and human populations. The H5N1 Hong Kong Flu in 1997 and H9N2 in 1999 have showed that avian influenza viruses can cross the receptor of host species boundary and transmit to human. Therefore, the specific aim of this study is to understand the frequency of inter-species transmission in Taiwan. Methods: We have established an avian influenza virologic surveillance system in one of the largest live poultry markets in Taipei City from October 1999 to March 2000. Serum samples were collected from 341 blood donors, including veterinarians, poultry farm workers, and market employees. HI and microneutralization were used to detect specific antibody against H6, an endemic virus in chicken farms in southern Taiwan, and antibodies against H3, H4, and H9 viruses. Results: Among about 1300 fecal specimens of chickens and ducks collected, we isolated 12 H3 viruses, 14 H4 viruses, and 2 H6 viruses (i.e. 9 serotypes of HA and NA) from ducks. The isolation rates were 0% (0/580) and 7% (28/400) in chickens and ducks, respectively. Phylogenetic analysis of HA from 7 of our 12 H3 isolates showed the highest (93%) homology with A/equine/Jilin/89 (H3N8). Both phylogenetic relationship of HA and NP genes from selected representative strains (7 H3, 7 H4, and 2 H6) found they all fell into Eurasian lineage of avian influenza viruses. Their NP genes were away from the G1 lineage that was found in H5N1 strain isolated in Hong Kong in 1997. In addition, the results of HI and microneutralization tests found that they were all seronegative against two avian influenza virus strains [A/Duck/Czechoslovakia/56 (H4N6) and A/Shearwater/Australia/1/72 (H6N5)]. Conclusion: Continuous efforts by integrating animal, market and human influenza surveillance systems have provided the best early warning signals to detect new influenza virus activities for preventing potential pandemics and providing effective controls.

In the United States, planning for the next influenza pandemic is occurring in parallel at national, state and local levels. Certain issues, such as conducting surveillance and purchasing pandemic vaccine, require coordination at the national level. However, most prevention and control actions will be implemented at the state and local level, which vary widely in terms of population demographics, culture (e.g., rural versus urban), and available resources. In 1995, a survey by the Council of State and Territorial Epidemiologists (CSTE) found that only 29 (59%) states perceived a need to develop a specific influenza pandemic plan for their jurisdiction. Since then, the process of developing state and local plans has gained considerable momentum. Integration of these efforts with the national planning process has been facilitated by: (1) the mutual involvement of state and federal staff in both processes; (2) the sharing of draft documents; (3) the ongoing occurrence of local and national coordinating meetings; and (4) the provision of financial resources by the federal government. So far, approximately 12 states either have drafted or begun drafting a state and local influenza pandemic plan. One of the benefits of the collaborative planning process has been the development of new working relationships and partnerships among several agencies at the state, local and national levels. Such efforts will improve our collective ability to rapidly investigate and control other emerging or re-emerging public health threats in the 21st century, be it a bioterrorist event, an influenza pandemic, or any other catastrophic health event.

PCR was used to amplify and sequence the complete HA1 region of the haemagglutinin (HA)-encoding genes of 10 clinical isolates of influenza virus of the H1N1 or H3N2 subtypes. These sequences were compared to those obtained from viruses isolated from the same specimens after passage in eggs and MDCK cells. Amino acid substitutions in the egg-derived HA sequences were found in nine out of the 10 specimens analysed, whereas seven out of eight of the MDCK-derived HA sequences were identical to those in the corresponding original specimens. Changes in the H1 HA occurred at residues 77a, 196 (also found in the corresponding HA from the MDCK isolate), 225, 226 and 227; changes in the H3 HA occurred at residues 137, 156, 186, 248 and 276. In addition, we have shown that an amino acid change at residue 145 in the HA of the H3 subtype that was previously demonstrated to be egg-selected is now present in circulating strains.

Eighteen strains of human influenza A (H1N1) viruses isolated between August 1986 and January 1991 were analyzed in this study. Examination of the total viral genome of 12 strains by T1 mapping revealed that considerable genetic heterogeneity exists among these viruses. Partial sequencing of each of the non-HA RNA segments of 4 viruses having divergent T1 oligonucleotide maps indicated that only one was a reassortant virus that had genes from both the influenza A (H1N1) and (H3N2) subtypes. This reassortant obtained its PB2 gene from a virus of the H3N2 subtype and the other 7 RNA segments from an H1N1 parent. Sequencing studies of the HA1 domains of the hemagglutinin (HA) genes of these 18 strains revealed that although these viruses are antigenically similar to the reference strains A/Taiwan/1/86 and A/Singapore/6/86, 7 conserved amino acid substitutions that are shared by recently isolated H1N1 viruses have occurred in the main stream of evolution of the H1N1 subtype. Our data indicate that: (1) Genetic reassortment continues to contribute to genetic variability of H1N1 viruses. (2) Genetic variants of non-reassortant H1N1 viruses are co-circulating in the world. (3) The HA's of recent H1N1 viruses are related to those of the 1986 reference strains. (4) Although there has been little detectable antigenic variability, the HA genes of human epidemic influenza A (H1N1) viruses have continued to evolve at an evolutionary rate similar to that for the H1N1 and H3N2 viruses analyzed previously.