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H1N1 in More Swine In Buenos Aires Argentina
The above comments describe the second pandemic H1N1 infection of swine near Buenos Aires (see map). This outbreak, southwest of the city, follows and earlier outbreak northwest of the city (see map). The above report confirms that these H1N1 outbreaks in swine (OIE report) are the pandemic strain, which was also reported for swine in Alberta.
Media stories suggested that the Alberta swine were from a farm worker who had visited Mexico and developed symptoms. However, the worker tested negative, casting doubt on the linkage between the worker and the infected herd. Moreover, a series of sequences from multiple isolates cast additional doubt on the link. Although all of these isolates were closely related to the pandemic strain, the heterogeneity in the swine sequences strongly suggests the herd was not recently infected.
Earlier reports had noted identity between NA sequences of the first New Jersey case, A/New Jersey/1/2009 collected in April, and a series of isolates from Japan, Sweden, and Spain collected in June and July. This level of identity was not seen among the Alberta swine sequences suggesting the swine were infected months ago.
The sequence data from Alberta, coupled with two distinct infections in Buenos Aires, Argentina, raise concerns that the pandemic H1N1 is widespread in swine. The three outbreaks above were not associated with swine deaths and therefore many infected swine may not be reported or tested.
The mild disease in swine may also help explain the database gaps. The pandemic H1N1 is related to other swine H1N1 isolates, but there is a gap in the level of relatedness, signaling large gaps in the database. The swine database is small, because of limited testing as well as hoarding of sequences, which would create gaps.
Recent sequence from Hong Kong were among the closest sequences, but many of the isolates were collectd years ago, indicating the sequences were not made public, or the samples held untested. However, in addition to the swine sequences in Asia, there are many withheld sequences from isolates in Canada, the United States, and Mexico, which also limits analysis.
Release of the sequences which have already been generated, and enhanced surveillance, would be useful.