CDC: ".evolving quickly" New Zeald-25;Spain-8,UK-1

Summary

• The situation is evolving quickly. 3 Countries have reported confirmed H1N1cases and 3 countries [New Zealand (25), Spain (8) and the UK (1)] report suspected H1N1 cases.

• In Mexico, 22 confirmed cases and 3 deaths have been confirmed as due to Influenza A/H1N1. Mexican health authorities have reported a total of 1455 suspected cases with 63 deaths which are currently under investigation.

• The United States has declared a public health emergency. 20 cases influenza A/H1N1 have been confirmed with no deaths.

• Today, countries worldwide are better prepared because of past achievements (such as improved surveillance, data collection, prepositioning of antiviral and other supplies, response plans and drills, etc.) in preparedness for pandemic influenza. All of these
efforts are being put to good use; the rapid response of countries worldwide is evidence of this.

Epidemiology

On April 18, 2009, the United States reported the 2 cases of human swine influenza in 9 and 10 year old children residing in the State of California (one in San Diego County, the other one in Imperial County).

Currently, 20 cases of human swine influenza have been confirmed in the United States (8 in New York, 7 in California, 2 in Texas, 2 in Kansas and 1 in Ohio). Other suspected cases are under investigation.

This virus has been described in the United States as a new subtype of the A/H1N1, not previously detected in either swine or humans.

In late March 2009, Mexico observed an unusual increase in severe acute respiratory infection which intensified during the first weeks of April. From April 17 to 26, 1,455 probable cases of influenza with severe pneumonia including 84 deaths were reported. The cases were registered in 24 out of the 32 States in Mexico. The majority of the probable cases of influenza with severe pneumonia were in the Federal District, Mexico and San Luis de Potosi States. The majority were young adults previously reported healthy. There have been few cases in individuals under 3 or over 59 years of age.

Until now 25 cases (out of 1455) of swine influenza A/H1N1 have been confirmed in reference laboratories in Winnipeg, Manitoba, Canada and in the CDC United States. The confirmed cases are from the Federal District (17), State of Mexico (6), Oaxaca (1) and Veracruz (1). There have been 5 deaths and 25 confirmed cases, 4 from the Federal District and one from the State of Mexico.

In Canada, there have been 4 confirmed human cases of swine influenza H1N1 in children in the province of Nova Scotia, some of them with a history of a recent travel to Cancun. All cases developed a mild form of the disease and have now recovered. The laboratory analysis was
performed by the laboratory in Winnipeg, Canada. Indigenous transmission has not been ruled out because not all cases have a history of traveling to Cancun.

In relation to the results in the first two cases confirmed by the United States, the viruses were isolated. They show a genetic recombination pattern of swine influenza virus in the Americas with a swine influenza virus of Eurasia. This particular gene combination had not been recognized previously. Both proved to be resistant to amantadine and rimantadine, but susceptible to neuraminidase inhibitors, oseltamivir and zanamivir. Both have been expanded in cell culture of low concentration of MDCK cells and inoculated in ferrets for the production of antisera. Five other viruses confirmed cases correspond to the new strain.

In conclusion:
• There is evidence of circulation of a strain not previously detected in either swine or humans.
• Currently the extension of the human-to-human transmission is under investigation.