Update on Influenza in the Americas

United States (USA): During Epidemiological Week (EW) 44 (from 25 October to 1 November 2003), the overall proportion of patient visits to sentinel providers for flu-like symptoms or influenza-like illness (ILI) was 2.2%, less than the national baseline of 2.5%. Of the total deaths occurring in the country, 6.3% were attributed to pneumonias and influenza.

During EW 44, WHO and NREVSS (USA National Respiratory and Enteric Viruses Surveillance System) collaborating laboratories tested 674 specimens for influenza viruses. Of these samples, 45 (6.7%) were positive, 4 with Influenza A Subtype H3N2 and 41 with Influenza A. Since 28 September 2003, a total of 4,371 samples have been tested, of which 193 (4.4%) were positive. Of these 193 positive samples, 190 (98%) were Influenza A viruses and 3 (2%) were Influenza B.

Source: Influenza Summary Update, Week ending November 1, 2003-Week 44. Website of the Centers for Disease Control and Prevention of the United States (CDC), National Center for Infectious Diseases (NCID).

Canada: During the Epidemiological Week ending on 1 November 2003 (EW 44), widespread influenza activity was reported in all regions in the Northwest Territories. Localized influenza activity was reported in all parts of Alberta and Saskatchewan and in one region of Ontario. Sentinel physicians reported 31 cases of influenza-like illness (ILI) for every 1000 patient visits, within baseline rates for EW 44 calculated at double the rate of the previous week. During the one-week period of 26 October 26 to 1 November 2003, Health Canada received 1,597 reports of laboratory tests for influenza most of which were for Influenza A (in Saskatchewan and Alberta). The National Microbiology Laboratory has antigenetically characterized 14 influenza viruses to date, of which all were similar to the A/Panama/2007/99 strain included in the vaccine for the 2003–2004 flu season. During EW 44, influenza outbreaks were reported in 3 schools in the Northwest Territories and 2 schools in Alberta, 1 hospital in Ontario and 4 LTC (long-term care) facilities. A total of 9,358 tests have been carried out this year, of which 580 turned out positive (578 with Influenza A and 2 with Influenza B).

Source: FluWatch, October 26 to November 1, 2003 (Week 44), Health Canada website: English   |   French.

Argentina: Up to 25 September 2003, the collaborating laboratories of the National Network of Influenza and Respiratory Viruses (Red Nacional de Influenza y Virus Respiratorios / RNIVR) processed 16,500 samples, detecting Influenza A in 1,138 of them and Influenza B in 20. The network referred to the National Influenza Center (Centro Nacional de Influenza / CNI) 894 positive samples, of which 880 (98.4%) were Influenza A and 14 (1.6%) were Influenza B. Subtyping of the Influenza A viruses showed a circulation of both Subtypes H3 (in 206 or 52%) and Subtype H1 (in 190 or 48%). Circulation peaked between EWs 20 and 27 (mid-May to late June), with Influenza A Subtype H1 viruses initially predominant followed by Subtype H3.

The majority of the Subtype H3 viruses (n=68) were similar to the A/Panama/2007/99 strain (H3N2). Eleven isolates responded to the anti-serum A/Korea/770/2002strain, related to the Panama strain. Both of these correspond to component A/Fujian/411/2002(H3N2) included in the Southern Hemisphere flu vaccine for 2004. All the viruses studied that belonged to Subtype H1 (n=47) were similar to the strain contained in the vaccine formulation being utilized, A/New Caledonia/20/99 (H1N1). Within this group, for the first time in the country, the circulation of Subtype H1N2 (n=26) was observed, its antigens similar to those of the original strains present in the 2003 vaccines. One isolate from La Plata was characterized as A/Hawai/15/2001(H1N2), a minor variant of A/New Caledonia. No Influenza B was characterized due to a lack of isolates.

Source: Information submitted to PAHO by the National Service of Viral Respiratory Diseases (Servicio de Virosis Respiratorias),National Institute of Infectious Diseases (Instituto Nacional de Enfermedades Infecciosas) / ANLIS "Dr. Carlos G. Malbran", Buenos Aires, Argentina.

Update on Severe Acute Respiratory Syndrome (SARS)

This past 5 November 2003, the WHO Consultation on SARS Vaccine Research and Development was held, involving the participation of more than 50 researchers from 15 countries. The group reviewed progress in the field and identified ways to accelerate the development and evaluation of SARS vaccines.

Most of the experts agreed that a safe and effective vaccine would be an important complement to existing SARS control strategies but that a SARS vaccine will not be available in time should an epidemic reoccur at the end of this year. In this regard, any possible resurgence of SARS should be handled through the control measures currently effective (surveillance, early diagnosis, hospital infection control, contact-tracing and international reporting).

The following subjects were discussed:

• The genetic variability of the SARS coronavirus, to identify the best strains to be included in future vaccines.
• Recent work involving experimental vaccines used on animals, and how that information can be used to initiate future clinical trials in human volunteers. The first clinical trial on an inactivated SARS vaccine could begin as early as January 2004. However, it is difficult to say when the vaccine might be available.
• Topics related to patents and intellectual property were discussed, along with preventive measures to facilitate these processes and ensure that, once developed, the vaccine would be universally available.
• Specific regulation measures were also discussed for the clinical evaluation and licensing for SARS vaccines.

For more information, see the source cited below.

Source: Global Search for SARS Vaccine Gains Momentum, online on the WHO SARS page.

Update on Yellow Fever in the Americas