The information contained within this update is obtained from data provided by Ministries of Health of Member States and National Influenza Centers through reports sent to Pan American Health Organization (PAHO) or updates on their web pages.
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I- Evolution of the pandemic
Regarding WHO qualitative indicators (See Annex 1) for monitoring of the pandemic, the three countries in North America report widespread geographic spread. There was an increasing trend of respiratory disease in Canada and Mexico, while decreasing in the Unites States. The intensity of acute respiratory disease was low to moderate in Canada and high in Mexico and the United States. The impact on Health Services was low in Mexico and moderate in the United States.
On its web page1, as of 8th October, Mexico reports increased activity of pandemic (H1N1) 2009 with the greatest number of cumulative laboratoryconfirmed cases in the Federal District, Chiapas, Yucatan, Jalisco, San Luis Potosi, Veracruz and Tamaulipas. When comparing against cases reported in the previous week (1st October), the greatest increases were observed in Durango, Morelos, Baja California Sur, and Puebla. It is important to note that Mexico is currently experiencing concurrent outbreaks of dengue and dengue hemorrhagic fever in several states.
In the United States, the influenza season began 12 weeks earlier than expected. The proportion of visits for influenza-like illness (ILI) has been above the baseline for EW 39 in all regions except two2 in the northeast. Regarding the geographical spread of the pandemic, 373 out of 50 states are experiencing geographically widespread activity (10 more than the previous week). Deaths attributed to pneumonia and influenza have now exceeded what is normally expected for this time of year. The United States has reported 12 cases of oseltamivir-resistant pandemic (H1N1) 2009.
Canada has experienced an increase in national ILI consultation rate since EW37 which has been above expected levels. Multiple outbreaks were reported, especially in schools settings. The highest activity of respiratory disease has been reported in the province of British Columbia with 11 influenza outbreaks, and in the Northwest Territories where two outbreaks were detected in schools. Canada has reported two cases of oseltamivir-resistant pandemic (H1N1) 2009.
1 Source: Mexico’s Health Secretariat http://portal.salud.gob.mx/contenidos/noticias/influenza/estadisticas.html, Accessed on October 8,2009
The two health Regions include the States of Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Vermont, Alabama, Alaska, Arizona, Arkansas, California, Colorado, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Minnesota, Mississippi, Missouri, Nebraska, Nevada, New Hampshire, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, South Dakota, Texas, Tennessee, Virginia, Washington, and Wyoming.
Cuba and Jamaica report widespread geographic spread while Bahamas and Dominica note regional spread and Saint Kitts and Nevis reported no activity. The trend of respiratory disease increased in most countries and the intensity of acute respiratory disease was high in Cuba and Dominica. The impact on health care services due to acute respiratory disease was both low and moderate.
Dominica has reported experiencing increased ILI activity and Saint Lucia reported influenza-associated outbreaks in the school setting during September.
Countries in this region reporting widespread geographic spread are Costa Rica, Nicaragua, and Panama, while in El Salvador the spread was regional. Trends in respiratory disease were decreasing or unchanged for all countries. The intensity of acute respiratory disease was mostly low or moderate while impact on heath care services due to acute respiratory disease was low in Guatemala, Nicaragua, Panama and mode rate in Costa Rica and El Salvador.
Belize reports experiencing a second wave of pandemic (H1N1) 2009 with increased ILI above expected levels for this time of year. Most patients are being seen in outpatient facilities with mild to moderate manifestations and the Districts of Belize, Cayo and Corozal mostly affected. Honduras also reports increased activity of influenza. Of note, El Salvador, Honduras, Nicaragua, Panama are detecting a recent increase in their cases of dengue fever as compared to the same time period last year. The current rainy South America In the Andean regions of South America, geographical spread was widespread. The trend of respiratory wasmainly decreasing or unchanged and the intensity was low or moderate. The impact on heath services waslow in Bolivia, Colombia, and Peru and moderate in Ecuador and Venezuela. Paraguay reported a different situation than the rest of the Southern Cone countries, as it experienced high intensity and moderate impact on health services. The rest of the Southern Cone countries presented low intensity and decreasing trend. In Chile, for example, of the 367,041 clinical cases and 12,252 confirmed cases since the beginning of the pandemic, only 121 clinical cases and two confirmed cases were detected in this week. Similarly, Argentina detected a decrease in hospitalizations for severe acute respiratory infection for the last ten weeks. Summary of Last Week
Belize reports experiencing a second wave of pandemic (H1N1) 2009 with increased ILI above expected levels for this time of year. Most patients are being seen in outpatient facilities with mild to moderate manifestations and the Districts of Belize, Cayo and Corozal mostly affected. Honduras also reports increased activity of influenza. Of note, El Salvador, Honduras, Nicaragua, Panama are detecting a recent increase in their cases of dengue fever as compared to the same time period last year. The current rainyseason favors the co-circulation of influenza and dengue viruses.
In the Andean regions of South America, geographical spread was widespread. The trend of respiratory wasmainly decreasing or unchanged and the intensity was low or moderate. The impact on heath services waslow in Bolivia, Colombia, and Peru and moderate in Ecuador and Venezuela.
Paraguay reported a different situation than the rest of the Southern Cone countries, as it experienced high intensity and moderate impact on health services. The rest of the Southern Cone countries presented low intensity and decreasing trend. In Chile, for example, of the 367,041 clinical cases and 12,252 confirmed cases since the beginning of the pandemic, only 121 clinical cases and two confirmed cases were detected in this week. Similarly, Argentina detected a decrease in hospitalizations for severe acute respiratory infection for the last ten weeks.
Summary of Last Week
II-Descriptions of hospitalizations and deaths among confirmed cases of pandemic (H1N1) 2009
A table containing case counts reported to PAHO is included in Annex 2. Among confirmed hospitalized confirmed cases (Table 1), approximately 40-50% were women. The most affected age group was those under the age of 40. Canada and Chile observed that 60% of hospitalized cases had underlying comorbidities but Paraguay observed a much lower range. Approximately 10-30% of these cases were in pregnant women.
In assessing the deaths among confirmed cases, women represent 45-60%(Table 2). The age deaths have taken place mostly among adults. More than two thirds of deceased cases had underlying comorbidities, while less than thirty percent of the deceased cases were in pregnant women.
III- Viral Circulation
For the purpose of this analysis, only countries which reported data on influenza A subtypes were considered.We excluded from the calculations of the percentages, results from samples of influenza A that were not subtyped or were unsubtypeable.
Pandemic (H1N1) 2009 appears to continue to be the influenza virus in circulation. The only country reporting a significant circulation of seasonal influenza viruses is Cuba.
IV- Clinical Issues
Clinical characteristics of hospitalized cases
Infrequently, hospitalizations and deaths have resulted from pandemic (H1N1) 2009 influenza virus. Jain et al. recently published an article in the New England Journal of Medicine describing clinical characteristics of patients hospitalized with 2009 (H1N1) pandemic influenza in the United States from April 2009 to mid-June 2009. Of the 272 cases studied, 25% were admitted to an intensive care unit and 7% died. Forty-five percent of the patients were children under the age of 18 years, and few (5%) severe illnesses were reported among persons 65 years of age or older. Nearly three quarters of the patients had one or more underlying medical conditions including asthma, diabetes, heart, lung, and neurologic diseases, and pregnancy. Of the 249 patients who underwent chest radiography on admission, 40% (n=100) had findings consistent with pneumonia. Of the 268 patients for whom data were available regarding the use of antiviral drugs, therapy was initiated in 200 patients (75%) at a median of 3 days after the onset of illness. Data suggest that the use of antiviral drugs was beneficial in hospitalized patients, especially when such therapy was initiated early.
This manuscript is available at: http://content.nejm.org/cgi/reprint/NEJMoa0906695v1.pdf
Infection control evidence: Surgical mask versus N95 respirator use for the prevention of influenza transmission To date, there is no consensus about the effectiveness of surgical mask as compared to N95 respirators for protecting health care workers (HCW) against influenza transmission.
Loeb M et al. published the results of a multicenter randomized trial in the Journal of the American Medical Association comparing N95 respirators with surgical mask use in HCWs. This clinical trial involved nurses working in medical units or pediatric units in eight Canadian tertiary care hospitals. Participants were evaluated for clinical and laboratory-confirmed respiratory illness using influenza serology and polymerase chain reaction (PCR) to detect a variety of respiratory viruses. Only 30% of nurses in each study group were vaccinated against influenza (trivalent influenza vaccine 2008-2009).
The results show that the incidence of influenza was similar in the two groups: surgical mask (23.6%) and N95 respirators (22.9%). In this study some factors were not addressed, for example, hand washing, the correct use of N95 respirators, and the implementation of respiratory or contact precautions. Despite some limitations, this is the first randomized trial to serve as a basis for identifying appropriate ways to protect HCWs.
Countries should provide specific attention to the implementation other strategies known to prevent the transmission of influenza in health care settings, such as administrative controls, application of standard and droplet precautions, and hand washing.
This manuscript is available at: http://www.who.int/csr/resources/publications/SwineInfluenza_infectioncontrol.pdf
As of 9 October, a total of 153,697 confirmed cases have been notified in all 35 countries in the Americas Region. A total of 3,406 deaths have been reported among the confirmed cases in 25 countries of the Region.
In addition to the figures displayed in Annex 1, the following overseas territories have confirmed cases of pandemic (H1N1) 2009: American Samoa. U.S. Territory (8); Guam U.S. Territory (1); Puerto Rico U.S. Territory (20); Virgin Islands U.S. Territory (49); Bermuda, UK Overseas Territory (1); Cayman Islands, UK Overseas Territory (14); British Virgin Islands, UK Overseas Territory (2); Turks and Caicos Islands (3); Martinique French, Overseas Community (44, 1 death); Guadeloupe, French Overseas Community (27); Guyane, French Overseas Community (29); Saint-Martin, French Overseas Community (19); Saint Bartholomew, French Oversease Community (2); Netherlands Antilles, Aruba (13); Netherlands Antilles, Bonaire (29); Netherlands Antilles, Curaçao (46)*; Netherlands Antilles, St. Eustatius (1); and Netherlands Antilles St. Maarten (22).
* Three cases were reported on a cruise-ship.
The distribution of cases and deaths at the first sub-national level can be found in the interactive map available through the following link: http://www.paho.org/hq/images/atlas/en/atlas.html
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Regional Update. Pandemic (H1N1) 2009. (published on October 9, 2009)