Pandemic H1N1 Spread in Argentina Raises Concerns

Commentary

Recombinomics Commentary 18:11
July 19, 2009

This virus in swine was reported to the OIE 1 Jul 2009 but is only
now, 16 days later, making the news and being declared an emergency.
It seems that emergencies are cautious declarations. - Mod.TG

The above comments are from a recent PROMed commentary on the second pandemic H1N1 on a swine farm in Argentina near Buenos Aires. The alert was issued by The National Agrifood Health and Quality (SENASA) after the second outbreak was confirmed. There first OIE report was an Immediate notification issued on June 25 for the outbreak in San Andrés de Giles (see map), which was followed by the July 1 cited above which provided more information for that outbreak. The alert was issued with the second follow-up report issued on July 8 for the outbreak at Cañuelas, which was a second distinct outbreak and was located southwest of Buenos Aires (see map).

The second outbreak near Buenos Aires followed a similar outbreak in Alberta, Canada. Media reports suggested the Alberta outbreak was linked to a farm worker who had returned from Mexico, but the worker tested negative and subsequent HA and NA sequences from the infected herd had considerable diversity, suggesting the swine had been infected at an earlier date, or form a hetergenous source, raising concerns that the pandemic strain was more widespread in swine. Since the farmer tested negative, there was no putative source sequence.

However, the swine sequences were closely related to the pandemic H1N1 which was clearly swine. Although an early PROMed commentary noted that the swine H1N1 had not been isolates in a swine, that failure was almost certainly linked to poor surveillance. Although PB1 had a human origin, which PB2 and PA had an avian origin, all three genes had been in swine 1-2 decades prior to the pandemic H1N1 outbreak. Therefore the surveillance shortfall prior to the outbreak may have been somewhat corrected by the sequences from the Alberta swine.

Similarly, the detection of pandemic H1N1 in swine on two farms outside of Buenos Aires may have provided additional examples of pandemic H1N1 in swine. Like Alberta, the detection of pandemic H1N1 on the two farms in Argentina also involve unconfirmed farm workers. No sequences from the swine outbreaks were released, and it remains unclear if any positive samples were collected from the workers.

The finding of pandemic H1N1 in swine on farms in Alberta Canada and farms in two distinct locations in Buenos Aires Argentina raises concerns that the virus is more widespread on farms, and increased surveillance in swine linked to symptomatic farm workers or symptomatic swine has led to the detection.

The alert in Argentina was issued in part because of limited surveillance and consequences of pandemic H1N1 in pork, which causes concern with regard to H1N1 evolution and spread. Swine acts as a mixing vessel and allows for pandemic H1N1 genetic exchanges with other serotypes such as H9N2 and H5N1. Although cooking kills H1N1, contaminated pork can contaminated cutting utensils and surfaces, leading to cross contamination in food that is nor cooked.

The two outbreaks in Buenos Aires is a concern because of the high rate for H1N1 deaths. Agency and media reports have described over 200 deaths, which have largely been reported in the past few weeks. Most of these deaths have been in Buenos Aires province or the adjacent Santa Fe province, raising concerns that the virus in the region has changed. Similarly one report suggest that as many as 10% of fatalities are in health care workers, which, if confirmed would be a major concern because health care workers would be more likely to be taking prophylactic Tamiflu or received time Tamiflu treatment, so frequent deaths could signal or more virulent virus.

Thus, release of sequences from the two outbreaks on the farms, as well as the recent explosion of fatal cases in Argentina would be useful