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
In Canada and the United States, spread of influenza continues to be widespread and trends of acute respiratory disease continue to increase.
In the United States, in EW 41, outpatient influenza-like-illness (ILI) activity continued to increase, remaining above the national baseline for the eighth consecutive week. Emerging Infections Program(EIP) laboratory-confirmed influenza hospitalizations rates remained high, especially in persons 5–49 years of age. The proportion of deaths attributed to pneumonia and influenza crossed the epidemic threshold for the first time in this influenza season in EW 40 and remained above this threshold.
A total of 95 pediatric deaths associated with pandemic (H1N1) 2009 have been reported to the Centers for Disease Control (CDC) since the emergence of the virus. Since August 30, 2009, CDC has received 53 reports of influenza-associated pediatric deaths; 47 of the 53 deaths were due to 2009 influenza A (H1N1) virus infections, and the remaining six were associated with influenza A virus for which the subtype is undetermined. This week, 11 influenza-associated pediatric deaths were reported to CDC—nine were associated with pandemic (H1N1) 2009 and two were associated with an influenza A virus for which the subtype is undetermined. Reports of pediatric influenza-associated deaths during the early fall are uncommon, but have occurred in the setting of geographically widespread high levels of pandemic influenza A (H1N1) in the United States. Seven of the 32 pediatric deaths (22%) had positive bacterial cultures; five of these were positive Staphylococcus aureus, of which three were methicillin-resistant. On Saturday, September 24, 2009, the United States declared a national emergency due to the pandemic.
Based on information available from Mexico’s webpage1, the greatest number of laboratory-confirmed cases was seen in the Federal District, Chiapas, Yucatan, Nueva Leon, San Luis Potosi, and Jalisco. As compared to the previous week (October 12), the greatest increases in confirmed cases were observed in Aguascalientes, Mexico, Durango, San Luis Potosi, and Jalisco. Of note, the states of Aguascalientes, Durango and Baja California Sur have experienced increases of more than 20% per week for at least the last three weeks.
In the Caribbean, acute respiratory disease activity has been variable with some countries reporting increasing trends in acute respiratory disease while others are reporting decreasing or unchanged trends. Overall, the intensity of acute respiratory disease and impact of acute respiratory disease on health care services is remaining low to moderate, with the exception of Belize which reported very high intensity of acute respiratory disease but a moderate impact of acute respiratory disease on health care services.
Cuba continues to report widespread influenza activity and increasing trends and high intensity of acute respiratory disease. Trinidad and Tobago reported their first pandemic-associated deaths last week (EW 40); in total, there have been 43 deaths in this region, including 22 in the Dominican Republic, and seven in Cuba.
In relation to the geographic spread of influenza, all countries except El Salvador reported widespread activity. The trend of acute respiratory disease is decreasing or unchanged in much of this region, with the exception of Guatemala, which reported an increasing trend. All countries are reporting low/moderate intensity of acute respiratory disease except Guatemala, which is reporting high intensity. The overall impact of acute respiratory disease on health care services was low or moderate in these countries. Several countries are reporting simultaneous outbreaks of dengue and cases of co-infection of both viruses are being investigated
All the countries providing an update this week reported widespread geographic spread of influenza. This week, Colombia reported a continued increasing trend of acute respiratory disease, while Ecuador reported a new increasing trend in acute respiratory disease. All reporting countries had a low or moderate intensity of acute respiratory disease and a low impact on health care services due to acute respiratory disease.
Most of these countries continued to experience a decreasing or unchanged trend of acute respiratory disease, with low/moderate intensity of acute respiratory disease, and low impact on health care services. Paraguay, however, reported a new increasing trend and high intensity of acute respiratory disease. Brazil reported an overall decreasing trend in acute respiratory disease and in severe acute respiratory illness (SARI) (97.3% decrease between EW 31 and 40) but also reported school outbreaks in the southern part of the country (Paraná). Since EW 36, Brazil reported an additional 469 pandemic-influenza associated deaths.
• The intensity of acute respiratory diseases in North America was high in Canada, Mexico, and the U.S.
• In Central America had a low or moderate intensity of acute respiratory disease; with the exception of El Salvador, which had a high intensity of acute respiratory disease and an increasing trend of acute respiratory disease
• Caribbean countries reported increasing or unchanged trends in acute respiratory disease, with outbreaks in schools.
• Most of South America had a decreasing trend and low or moderate intensity of acute respiratory disease; Colombia, however, had an increasing trend in acute respiratory disease
• 81.95% of subtyped influenza A viruses were pandemic (H1N1) 2009
• 133 new confirmed deaths in 10 countries (3539 cumulative deaths)
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.
Approximately half of confirmed hospitalized confirmed cases were among women (Table 1), while children were the age group with highest hospitalization rates. Underlying comorbidities were present in 50- 60% of hospitalized cases, while approximately 25% of confirmed cases in child-bearing age women were pregnant.
In assessing the deaths among confirmed cases, women represent approximately 45–60% of these cases (Table 2). Deaths have taken place mostly among adults. More than two-thirds of deceased cases had underlying comorbidities.
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.
In the countries providing this information, there is a continued predominant circulation of the pandemic (H1N1) 2009 virus.
In temperate regions, the proportion of pandemic (H1N1) 2009 virus amongst all subtyped A viruses remained stable from EW 21 through EW 40 (Graph 1). In contrast, in the tropical regions, the replacement of seasonal influenza A subtypes took place gradually over this same time period (Graph 2).
This week, Barbados and El Salvador reported cases co-infected with influenza (H1N1) 2009 and dengue, which are under investigation. PAHO also received notification of suspected cases, co-infected with influenza (H1N1) 2009 and dengue from other countries.
Pregnancy highlighted as risk factor in the WHO International Consultation on Clinical aspects of Pandemic (H1N1) 2009
To gather information about the clinical features and management of pandemic influenza, PAHO/WHO hosted a meeting in Washington DC from 14-16 October 2009. Findings and experiences were presented by more than 100 international clinicians, scientists, and public health professionals with a broad representation from the Americas Region.
Participants agreed that the risk of severe or fatal illness is highest in three groups: pregnant women, especially during the third trimester of pregnancy, children younger than two years of age, and people with chronic lung disease, including asthma.
Although there is no significant gender difference among the hospitalized cases, country data from the Americas suggest that 20–25% of child-bearing age confirmed hospitalized cases were pregnant2. This proportion is similar among fatal cases 2.
Health care providers of antenatal services should pay special attention to the signs and symptoms of respiratory infection among pregnant women. Early clinical suspicion, followed by oseltamivir treatment without delay, is considered a recommended intervention3 to prevent severe cases and deaths related with influenza in pregnancy. Differences in the influenza lethality among pregnant women from different countries could be related to the early access to antiviral medication and additional clinical measures. Oxygen saturation below 94% is considered an alert sign for prompt referral to a higher health care level and oxygen therapy. Chest X-ray is considered safe in the last trimester of pregnancy, as expressed by the experts in the last WHO International Consultation held in Washington, DC.
Primary prevention of influenza among pregnant women should be also emphasized. As prioritized group for influenza vaccination, pandemic H1N1 vaccine should be administered as recommended in national protocols. Infection control measures at the community level, such as respiratory etiquette, hand hygiene and frequent ventilation of the households should be promoted. If a family member develops a respiratory infection, distancing of 1-2 meters is necessary to avoid transmission. Pregnant women should not take care of household members with by respiratory infections.
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As of 23 October, a total of 174,565 confirmed cases have been notified in all 35 countries in the Americas Region. A total of 4,175 deaths have been reported among the confirmed cases in 26 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 territories: American Samoa (8); Guam (1); Puerto Rico (20) and U.S. Virgin Islands (49). 2. United Kingdom Overseas Territories: Bermuda (1); Cayman Islands (104, 1 death); British Virgin Islands (12); Turks and Caicos Islands (36). French Overseas Communities: Martinique (44, 1 death); Guadeloupe (27); Guyane (29, 1 death); Saint Martin (30); Saint Bartholomew (2); Netherlands Antilles: Aruba (13); Bonaire (31); Curaçao (53)*; St. Eustatius (1); and St. Maarten (24).
* 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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