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.
To download the full report in PDF please click here
I- Evolution of the pandemic
Widespread influenza activity and increased trends in acute respiratory disease continued this week.
In Canada, the national influenza-like illness (ILI) consultation rate increased again relative to the last week and remained above average for the fifth consecutive week. There was another sharp increase in the number of influenza outbreaks and these continued to be reported mostly in school settings. The proportion of tests positive for influenza again increased this week to 36.3% from 29.0% (EW 42).
In the United States, ILI consultations decreased slightly but remained well above the national baseline. Laboratory-confirmed influenza hospitalization rates remained high, especially in persons 5–49 years of age. The proportion of deaths attributed to pneumonia and influenza remained above the epidemic threshold for the fifth consecutive week. Five of ten subnational surveillance regions reported decreases in proportion of outpatient visits for ILI as compared to the previous week, but all ten reported a the ILI proportion to be above their region-specific baseline. A total of 18 influenza-associated pediatric deaths were reported this week, of which 15 were associated with the pandemic virus.
Mexico reported a large number of confirmed cases and deaths this week, but the overall trend of the epidemic curve1 appears to shift downward based on the number of confirmed cases. Also, the greatest number of laboratory-confirmed cases1 was seen in the Federal District, Chiapas, Yucatan, Nueva Leon, San Luis Potosi, and Jalisco.
These countries continue to report variable spread of influenza and variable trends in acute respiratory disease. Intensity of acute respiratory disease was reported as both high and low/moderate, while impact of acute respiratory disease on health care services was reported as both low and moderate.
In countries providing these data, severe acute respiratory infection (SARI) hospitalization rates2 continued to increase for the fourth consecutive week, reaching the highest rate this year in EW 42. In the French Overseas Territories, ILI activity has been variable, with some Territories reporting decreases in activity while others are reporting increases.
This week, trends of acute respiratory disease remained unchanged or were decreasing. Intensity of acute respiratory disease remained low/moderate and impact of acute respiratory disease on health care services was low.
These countries continued to report widespread influenza activity. The majority of the countries reported decreasing trends in acute respiratory disease. Colombia, however, continues to report increasing trend. Overall, intensity of acute respiratory disease remained low/moderate as did impact of acute respiratory disease on health care services.
Venezuela reported an outbreak of acute respiratory infection in indigenous Yanomami communities. More details on this outbreak are included in section IV of this report.
Argentina reported pockets of influenza activity in parts of Buenos Aires and Santa Fe, with twelve new confirmed cases, two deaths, and several ILI cases currently under investigation. Of note is that Argentina reported 1,013 new confirmed cases this week, but only 12 correspond to cases with symptom onset this week, and the remainder are cases that were laboratory confirmed this week.
In the other countries, there were no significant changes in trends of acute respiratory disease activity as compared to last week and most countries experienced a decreasing or unchanged trend of acute respiratory disease, with low/moderate intensity of acute respiratory disease, and low/moderate impact on health care services.
•The trends of acute respiratory disease in North America increased or were unchanged; there were 18 influenza-associated pediatric deaths reported in the United States this week
• Caribbean countries reported variable trends in acute respiratory disease this week
• Central America continues to report overall decreasing trends in acute respiratory disease
• Most of South America had stable or decreasing trends of acute respiratory disease, with the exception of Colombia, which again reported an increasing trend and Argentina, which reported pockets of influenza-like illness activity in Buenos Aires and Santa Fe
• Venezuela and Brazil are investigating cases of acute respiratory infection in the indigenous Yanomami community
• A median of 99.7% of subtyped influenza A viruses were pandemic (H1N1) 2009
• 113 new confirmed deaths in 8 countries were reported; in total there have been 4,512 cumulative
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 hospitalized cases were among women (Table 1). Children and young adults continue to be the age group with highest hospitalization rates. Underlying comorbidities were present in approximately 60% of hospitalized cases, while approximately 20% of confirmed cases in child-bearing age women were pregnant.
Approximately half of deceased cases were among women (Table 2), and overall, most deaths were among adults. The percentage of cases with underlying co-morbidities varied from 62.5% to 76.9%
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.
Circulation of pandemic (H1N1) 2009 is still predominant, except for Chile, where no pandemic (H1N1) 2009 was reported this week (Table 3). In the Caribbean (Table 4), to date, the majority of subtyped influenza A was pandemic (H1N1) 2009.
Since the appearance of the pandemic virus (EW 16), the proportion of pandemic virus amongst all subtyped A viruses has been increasing. Initially, from EW 21 through EW 30, the proportion of pandemic virus was 70% to 90%, but since EW 31, has consistently been greater than 90%. Of note, since EW 32, the total number of subtyped influenza cases has been decreasing, coincident with the conclusion of the Southern Hemisphere winter season.
On October 30th Venezuela reported the detection of an outbreak of Acute Respiratory Infection (ARI) in various communities of the Yanomami indigenous groups, of the parish of Mawaca, in the High Orinoco municipality of the Amazon State (Venezuela). This municipality extends 50,300 Km2, with an approximate population of 18,538 inhabitants, which are predominantly of the following indigenous groups: Yanomami, Yekwuana, Piaroa, and Arahuacos. The Yanomami is the most numerous group with 12,049 inhabitants. The population density is of 0.36 inhabitants x Km2.
Due to the outbreak, a multidisciplinary and multi-ethnic team was deployed for the epidemiological investigation that included active case-finding, provision of healthcare, and implementation of control measures. Ill persons were found to that the clinical symptoms consistent with influenza-like illness, which was accompanied by diarrhea in some children. From 21 October to 03 November there were 1,004 cases of ARI, 265 cases of pneumonia, and 8 deaths were reported to be associated with this outbreak. The epidemic curve of the outbreak reveals a peak on 26 to 28 October 2009.
During the investigation, nine clinical specimens were obtained, two of which were from fatal cases. Of the 9 samples tested, six were negative for influenza, one was positive for seasonal influenza, and two were positive for pandemic influenza (H1N1) 2009. The confirmed pandemic (H1N1) 2009 cases were from Platanal and have recovered. The specimens from the fatal cases were both negative for influenza A.
As part of control measures, treatment with oseltamivir was initiated in symptomatic cases and chemoprophylaxis was provided to contacts given the high household density.
Of note, prior to the beginning of the outbreak two events that increased the risk of transmission were held in the High Orinoco municipality. The first was a day where community workers provide healthcare and the second was a sporting event. These activities resulted in increased contact between communities and people from other regions of the country.
Venezuela will continue its investigation and provision of care for all in this municipality, and strengthen its culturally-sensitive epidemiologic surveillance system that involves the utilization of trained community health workers.
Yanomami health district in Brazil has also detected an increase in cases of influenza-like illness (ILI) in its Yanomami population, but no pandemic (H1N1) 2009 has been identified. This district includes eight municipalities in the states of Roraima and Amazon (Brazil), extending 9,664,975 hectares. The population is estimated to be 18,766 people from the Yanomami and Yekwuana ethnic groups.
As of 6 November, a total of 190,765 confirmed cases have been notified in all 35 countries in the
Americas Region. A total of 4,512 deaths have been reported among the confirmed cases in 27 countries of the Region. Saint Lucia reported the first death in a confirmed case.
In addition to the figures displayed in Annex 2, 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: Anguilla (10); Bermuda (15); Cayman Islands (104, 1 death); British Virgin Islands (15); Turks and Caicos Islands (38). French Overseas Communities: Martinique (44, 1 death); Guadeloupe (27, 1 death); Guyane (29);Saint Martin (70); Saint Bartholomew (2); Netherlands Antilles: Aruba (57); Bonaire (34); Curaçao (55)*; Saba (1); St. Eustatius (1); and St. Maarten (26).
* 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
Download full report
Regional Update. Pandemic (H1N1) 2009. (published on November 9, 2009)