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Epidemiological AlertsVol. 6, No. 20

icon Update Influenza A (H1N1) Regional Report (4 May 2009)

To date, the total of confirmed cases of influenza A (H1N1) recorded is 1,118, including 27 deaths, in 6 countries of the Americas (Mexico, United States, Canada, Costa Rica, Colombia and El Salvador).

To date, the United States has confirmed a total of 286 human cases of influenza A (H1N1): 4 in Alabama, 17 in Arizona, 30 in California, 7 in Colorado, 2 in Connecticut, 20 in Delaware, 5 in Florida, 1 in Idaho, 8 in Illinois, 3 in Indiana, 1 in Iowa, 2 in Kansas, 1 in Kentucky, 14 in Louisiana, 4 in Maryland, 6 in Massachusetts, 2 in Michigan, 1 in Minnesota, 1 in Missouri, 1 in Nebraska, 1 in Nevada, 1 in New Hampshire, 7 in Nueva Jersey, 1 in Nuevo México, 73 in Nueva York, 1 in North Carolina, 3 in Ohio, 3 in Oregon, 1 in Pennsylvania, 1 in Rhode Island, 15 in Carolina del Sur, 1 in Tennessee, 41 in Texas, 1 in Utah, 3 in Virginia and 3 in Wisconsin. Other suspected cases are being investigated. One death has been registered, a child of 22 months old. The age range of the confirmed cases is from 22 months to 81 years.

From 17 April to 2 May, Mexico has reported 727 confirmed cases of influenza A (H1N1), including 26 deaths. The states with the highest number of confirmed cases are Distrito Federal, Estado de Mexico, San Luis Potosi and Hidalgo. . The majority of these have occurred in previously healthy young adult people. There have been few cases in individuals under 3 or over 59 years old.

In Canada, to date 101 human cases of influenza A (H1N1) have been confirmed (18 in Alberta, 29 in British Columbia, 1 in New Brunswick, 33 in Nova Scotia, 3 in Quebec, 1 in Manitoba and 16 in Ontario) some of them with recent trip history to Cancun, Mexico. All the cases developed a mild form of influenza like illness. 2 of the cases presented, in addition, gastrointestinal symptoms. All of them are currently recovered and none required hospitalization. Laboratory tests were conducted in Winnipeg, Canada. Indigenous transmission is not discarded since not all the confirmed cases have trip history to Mexico

On 2 May, Costa Rica notified 1 confirmed case of influenza A (H1N1) On 3 May, Colombia reported 1 confirmed case of influenza A (H1N1), while El Salvador reported 2 confirmed cases of influenza A (H1N1).

The press has reported information on suspected cases in several countries of the Region; however this information has not been confirmed. 2

International Health Regulations (IHR)

The Director-General of WHO determined on 25 April that this event constitutes a Public Health Emergency of International Concern. On 29 April, the Director General decided to raise the pandemic alert to Phase 5.

The DG recommends not closing borders or restricting travel. However, it is prudent for people who are sick to delay travel. Moreover, returning travelers who have become sick should seek medical attention in line with guidance from national authorities.


Enhanced surveillance

At this time, enhanced surveillance is recommended. On its Web page, PAHO has published orientations for the enhancement of surveillance activities, which are directed to the investigation of:

  • Clusters of cases of ILI/SARI of unknown cause
  • Severe respiratory disease occurring in one or more health workers
  • Changes in the epidemiology of mortality associated with ILI/SARI; increase of observed deaths by respiratory diseases; or increase of the emergence of severe respiratory disease in previously healthy adults/adolescents.
  • Persistent changes observed in the response to the treatment or evolution of a SARI.

The following risk factors should also cause suspicion of influenza A (H1N1):

  • Close contact with a confirmed case of influenza A (H1N1) while the case was sick.
  • Recent travel to an area where there are confirmed cases of influenza A (H1N1) have been confirmed

Virological surveillance of influenza A (H1N1)

It is recommended that National Influenza Centers (NIC) immediately submit to their regular WHO Collaborating Center for influenza all positive but unsubtypable specimens of influenza A. Shipment procedures are the same as those used by NICs for seasonal influenza specimens.

The test protocols for the detection of seasonal influenza by Polymerase Chain Reaction (PCR) cannot confirm influenza A (H1N1) cases. The Centers for Disease Control and Prevention of the United Sates (CDC) has begun to ship testing kits that will include the primers and probes as well as the required positive control samples.

Current available evidence indicates that the technique of Immunofluorescence (IF) has low sensitivity for the identification of the new influenza A virus (H1N1). As a result, its results are not recommended as a basis to rule out suspected cases. Furthermore, the suspected cases with positive results for influenza A, but unsubtypable, obtained by PCR have a high probability of being confirmed as cases of the new influenza A virus (H1N1).

Infection prevention and control in health care facilities

Since the main form of transmission of this disease is by droplets it is recommended strengthening the basic precautions to prevent their dissemination, for example the hygiene of hands, adequate triage in the health facilities, environmental controls, and the rational use of the personal protective equipment in accordance with the local regulations.

The complete guides "Epidemic-prone & pandemic-prone acute respiratory diseases Infection prevention & control in health-care facilities" are available at:

Influenza HA1N1

Last Updated on Tuesday, 05 May 2009 12:02

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