Influenza update, 06 July 2012 - Update number 163 (WHO, edited)

[Giuseppe]

[Source: World Health Organization, full page: (LINK). Edited.]

Influenza update, 06 July 2012 - Update number 163



Summary

• The influenza season is largely finished in the temperate countries of the northern hemisphere and most countries in the northern temperate zone have now stopped weekly reporting. A detailed review of the recent influenza season in the temperate countries of the northern hemisphere is available online here
• In the tropical zone, Brazil, Paraguay and Honduras have reported notable influenza activity in the Americas; Ghana in sub-Saharan Africa; and southern China, including Hong Kong Special Administrative Region, and Vietnam in Asia.
• The influenza season has commenced in most temperate countries of the southern hemisphere for which there is data. In Argentina, however, influenza remains nearly undetectable and although New Zealand has reported persistent increases in influenza virus detections over the last three reporting weeks, influenza-like illness (ILI) reports remained below the national baseline.
• Influenza A(H3N2) viruses were the most commonly reported type/sub-type in recent weeks in the Southern Hemisphere temperate region in Chile, South Africa, and Australia; however, significant numbers of influenza type B were also reported in South Africa and to a lesser extent, Australia. Very few influenza A(H1N1)pdm09 viruses have been reported in the temperate region however A(H1N1)09 is currently the most commonly detected virus in active countries of Central and tropical South America.

-Full version Epidemiological influenza surveillance update pdf, 660kb

- Virological influenza surveillance update

Review of the 2011/2012 northern hemisphere influenza season pdf, 1.76Mb

Peer-reviewed literature Estimated global mortality associated with the first 12 months of 2009 pandemic influenza A H1N1 virus circulation: a modeling study



Source of data

The Global Influenza Programme monitors influenza activity worldwide and publishes an update every two weeks.

The updates are based on available epidemiological and virological data sources, including FluNet (reported by the Global Influenza Surveillance and Response System) and influenza reports from WHO Regional Offices and Member States.


Completeness can vary among updates due to availability and quality of data available at the time when the update is developed.

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[Giuseppe]

Re: Influenza update, 06 July 2012 - Update number 163 (WHO, edited)

[Source: World Health Organization, full PDF document: (LINK). Extracts.]

Influenza Update N? 163 - 06 July 2012


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Countries in the tropical zone

Tropical countries of the Americas

Some active transmission of influenza has been reported in Central America, the Caribbean, and tropical South America.

In Central America, El Salvador continued to report elevated levels of influenza A(H1N1)pdm09 detections. In the past week, 29% (19/65) of all specimens tested were positive for influenza and A(H1N1)pdm09 accounted for 89% (n=17) of influenza viruses.

Influenza A(H1N1)pdm09 has also been circulating recently in Honduras and Panama, though numbers of viruses detected were low and transmission appears to have peaked in May.

In the Caribbean, circulation of influenza A(H3N2) has decreased to low levels in Dominican Republic compared with previous weeks.

In Cuba, detections of influenza B, the predominate virus type, continued to increase in comparison with previous weeks.

Jamaica has also reported influenza B circulating in low levels since late May.

In the tropical zone of South America, the Plurinational State of Bolivia reported a continued increase of positive influenza detections in the region of La Paz, where more than 50% of clinical samples collected in the past reporting week were positive for influenza. All of the influenza viruses detected were influenza A(H1N1)pdm09. The proportion of hospitalizations due to severe acute respiratory infection (SARI) has also increased since the previous week.

Brazil also reported a sustained increase of positive influenza detections since mid-May. This has been associated with a notable
increase in reports of SARI, primarily in the southern part of the country. Of influenza positive SARI cases 80% (790/979) have been associated with influenza A(H1N1)pdm09 and the remainder with A(H3N2).

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Tropical Asia

Most countries of tropical Asia continued to report influenza activity at a low or undetectable level.

In south China the percentage of visits with ILI to national sentinel sites was unchanged in comparison to the last three weeks values, though it remained elevated (3%) in comparison to the same period of the previous two years.

Influenza A(H3N2) was the most commonly detected virus, accounting for 81% of all subtyped influenza viruses.

Influenza activity in Hong Kong Special Administrative Region, which recently reported unusually persistent high level influenza activity, now appears to be decreasing. In the period from 17 June to 23 June 2012, there has been a decrease influenza-like illness (ILI) presenting to outpatient clinics, private doctors, and emergency departments along with a decrease in the rate of influenza-associated hospital admissions and mortalities in comparison to previous weeks.

Vietnam has also reported active transmission of influenza A(H3N2) for the past several weeks. In June, 43% (52/121) of ILI cases tested were positive for influenza of which 88% (n=46) were H3N2 and 12% (n=6) were influenza B. Of these, In addition, 40 SARI cases were also tested, of which 25% (n=10) were positive for influenza, five each of A(H3N2) and influenza type B virus.

Singapore also has reported some influenza transmission. The overall prevalence of influenza among ILI samples (n=164) in the community was 66% in the past four weeks. Of all the positive samples tested in May 2012, influenza B constituted 52%, while influenza A(H3N2) and influenza A(H1N1)pdm09 accounted for 30% and 18%, respectively.

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Temperate countries of South America

Influenza activity in the southern cone of South America has continued to increase in recent weeks in Chile, however, the influenza season does not appear to have started yet in Argentina.

Chile reported further increasing detections of influenza when compared to previous weeks, at the same time respiratory syncytial virus (RSV) detections have been increased. ILI activity has now increased to near their alert threshold and the percentage of emergency visits for respiratory disease has now reached 31%, exceeding values reported for the same period in the last two years. Nearly all of the influenza viruses detected in Chile have been A(H3N2) so far this season.

In Paraguay, numbers of ILI consultations continued to increase but have not reached alert thresholds compared to the last 2 weeks and 36% of154 clinical specimens tested were positive for influenza.

In contrast to Chile, influenza A(H1N1)pdm09 accounts for 79% of influenza virus detections in Paraguay with much smaller amounts of A(H3N2) and influenza type B.

In Argentina, only small numbers of influenza viruses have been sporadically detected so far this season; ILI, SARI, and pneumonia cases have all increased. However, this has primarily affected children under 5 years of age and is associated with large numbers of respiratory syncytial virus (RSV) detections; influenza activity remained essentially undetectable.

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