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Update on Influenza in the Americas
United States of America (USA): During Epidemiological Week (EW) 42 (from 12–18 October 2003), the overall proportion of visits to sentinel providers by patients suffering from influenza-like illness (ILI) was 1.9%, a rate less than the national baseline of 2.5%. The proportion of deaths attributed to pneumonia and influenza was 6.3%. One State Health Department (Texas) reported widespread influenza activity; 5 states and New York City reported sporadic influenza activity; and 40 states and the District of Columbia reported no influenza activity.
For this week, the US Office of the World Health Organization (WHO) and the National Respiratory and Enteric Virus Surveillance System (NREVSS) Collaborating Laboratories reported 520 specimens tested for influenza viruses, of which 15 (2.9%) were positive. Of these, 11 Influenza A (H3N2) and 4 non-subtyped Influenza A viruses were identified. Since 28 September 2003, WHO and NREVSS laboratories have tested a total of 1,980 specimens for influenza viruses, of which 70 (3.5%) were positive. Of the 70 viruses identified, 69 (99%) were Influenza A viruses and only one (1%) was an Influenza B virus. Of the 69 Influenza A viruses, 14 (20%) have been subtyped; all were Influenza A (H3N2) viruses. For October, 6 states have reported laboratory-confirmed influenza. Influenza A viruses have been identified in the states of Arkansas, Louisiana, New York, Texas, and Washington; an Influenza B virus has been identified in Hawaii.
Source: Influenza: Reports and Surveillance Methods in the United States. Centers for Disease Control and Prevention of the United States (CDC), National Center for Infectious Diseases.
Canada: During the week ending on 18 October 2003 (EW 42), sentinel physicians reported 15 cases of influenza-like illness per every 1,000 patient visits, a rate below baseline rates for that week. During the one-week period of 12–18 October 2003, Health Canada received 1,023 reports of laboratory tests for influenza, of which 87 (8.5%) detected Influenza A (in Saskatchewan and Alberta) but without any detecting Influenza B (see table). During EW 42, influenza outbreaks were reported in 2 schools and 1 long-term care (LTC) facility in Alberta; and in Saskatchewan, and 3 outbreaks were reported in 1 school and in 2 LTC facilities. For 2003, a total of 6,285 tests have been performed, of which 175 turned out positive (174 Influenza Virus A and one Influenza Virus B).
Source: FluWatch, October 12 to October 18, 2003
(Week 42), online in English edition and Édition française. Health Canada.
Chile: Since EW 12 (16–22 March 2003), there has been an increase in the number of reported cases, rising to a high of 285 cases during the week of 20–26 July 2003 (at a rate of 28.6 per every 100,000 inhabitants). Since 2 August 2003, a downward trend has been observed in almost all the regions, except in Maule where reports of influenza increased at the end of September. For 2003, cases of influenza have also been reported in Antofagasta, La Serena, Viña, Valparaíso, San Fernando, Linares, Concepción, Talcahuano, Valdivia, Osorno, Puerto Montt, Aysén and Punta Arenas. A strain of Influenza A has been typified similar to strain A/Panama/2007/99 (H3N2), which is included in the vaccine for the 2003 season. Also typified were strains of Influenza A (H1) and B (with only one case for the time being). In the week from 19–25 October 2003, sporadic activity has been detected, with 2 cases of Influenza A in Talcahuano and 1 in Concepción.
Sources
Argentina: Reports received up to 24 October 2003 indicate that 848,232 cases of influenza have been reported. The provinces with greater number of cases are Buenos Aires (with 243,736 cases) and Córdoba (with 100,104 cases).
Source: Boletín semanal de notificaciones
(24 de octubre de 2003, semana epidemiológica Nº 42 (Weekly Bulletin of Reports, 24 October 2003, EW 42). Sistema Nacional de Vigilancia Epidemiológica (
SINAVE), Dirección de Epidemiología, Ministerio de Salud de Argentina (National System of Epidemiological Surveillance, Epidemiological Division, Ministry of Health of Argentina) (in Spanish).
Mexico: To 18 October 2003, 130 cases of influenza have been reported. The states with the greater number of cases are the Federal District (Distrito Federal/DF, or Mexico City, with 88 cases) and Yucatán (with 16 cases). Viral activity has been detected in other states as well (Campache, Hidalgo, Mexico, Michoacán, Nayarit, Nuevo León and Sonora). In the week of 12–18 October 2003, a single case was reported.
Source: Boletín Epidemiológico de México, Semana 42, del 12 al 18 de octubre del 2003 (Estadísticas en salud) (Epidemiological Bulletin of Mexico, Week 42 from 12–18 October 2003; Health Statistics). (in Spanish).
French Guiana and Uruguay: Viral activity has also been detected in French Guiana (EWs 40 and 41) and Uruguay (EW 40).
Source: Country Reports for the 2003–2004 Season. WHO FluNet, World Health Organization (WHO).
Update on West Nile Virus (WNV) in the Americas
USA: During the week running from 23–29 October 2003, a total of 332 human cases of WNV infection were reported from 22 states, including 11 fatal cases from 3 states. In addition, WNV infections were reported in 330 dead birds, 450 mosquito pools, and 147 horses.
For 2003, a total of 7,718 human cases of WNV infection have been reported. The states with the highest number of cases are Colorado (2,170), Nebraska (1,540), and South Dakota (964). Of the 7,588 (98%) cases for which demographic data is available, 4,012 (53%) occurred among males; the median age is 47 years. Detailed up-to-date information is available for 7,588 cases, of which 5,025 cases (66%) were reported as West Nile Fever (a milder disease) and 2170 (29%) as West Nile Meningitis or Encephalitis (a severe disease).
Sources: CDC Website.
Canada: To 30 October 2003, 443 cases from WNV infection have been confirmed in 7 provinces, including 10 deaths. Two of the provinces have reported probable imported cases. Of these, 260 correspond to the province of Alberta, 88 to Ontario, 38 to Saskatchewan, and 35 to Manitoba. There are 832 cases still under study, of which 729 are from Saskatchewan and 103 from Manitoba.
No new suspected or confirmed cases have occurred in horses since the last two updates on 23 and 16 October 2003. The total number of suspected or confirmed cases remains at 445. On birds, 11,280 serological tests have been performed, with 1,628 confirmed WNV infections; this implies the appearance of 9 new cases having been confirmed this week. Regarding mosquito pools infected with WNV, 570 have been identified. The provinces affected are the same as for previous weeks.
In total, these figures—together with the reduction of the number of new human cases and the absence of new equine cases and WNV-positive mosquito pools—indicate that the end of the outbreak is imminent, coincident with falling temperatures.
Source: West Nile Virus Surveillance Information: English | français. Health Canada.
Mexico: Up to 30 October 2003, 505 human serological tests have been carried out in 22 states, with 4 people showing positive results, 3 in Chihuahua and 1 in Sonora (confirmed by RT-PCR testing). Out of 32 states, 20 have detected equine WNV activity, with a total number of 1,805 positive and asymptomatic cases and 1 positive dead horse. In birds, 8 states have performed tests to detect WNV, with a total number of 102 positive cases out of 17,369 tested and 2 dead positive birds.
Source: Virus del Oeste del Nilo (West Nile Virus). Programa de Acción para la Prevención y Control de las Enfermedades Transmitidas por Vector de México, Secretaría de Salud de México (Action Program for the Prevention and Control of Vector-Borne Diseases in Mexico, Secretary of Health of Mexico) (in Spanish).
Additional Note: Besides the United States, Canada, and Mexico, there has been native circulation of WNV in El Salvador (horses, 2003), the Dominican Republic and Jamaica (birds, 2002–2003), and in Guadeloupe (horses and birds, 2002–2003).
- Sources
- - Emerging Infectious Diseases, 2003 9 (7): 860–863.
- - Science Now, March 2003.
- - Direction générale de la Santé, Point presse "Dossier d'actualité in sécurité sanitaire", 26 mai 2003.
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