A ProMED-mail post
Date: Mon 14 Oct 2013
Source: WHO surveillance & monitoring update 196 [edited]
Influenza Update No. 196 - 14 Oct 2013
in many European countries influenza-like illness activity started to
increase, influenza activity in the northern hemisphere temperate zones
remained at inter-seasonal levels.
In most regions of tropical
Asia, influenza activity was at a low level, with the exception of Hong
Kong Special Administrative Region, China, where influenza transmission
increased due to influenza A(H3N2).
In the Caribbean region of
Central America and tropical South American countries, cases of
influenza decreased, while acute respiratory illness remained stable in
the Caribbean and Central America. Respiratory syncytial virus (RSV)
predominated, but the RSV activity remained within expected seasonal
Influenza activity peaked in the temperate countries of
South America and in South Africa in late June 2013. Temperate South
American countries reported acute respiratory disease activity within
expected seasonal levels, and RSV activity largely declined.
Australia and New Zealand, numbers of influenza viruses detected and
rates of influenza-like illness seemed to have peaked. Co-circulation of
influenza A(H1N1)pdm09, A(H3N2) and B viruses was reported in both
Additional and updated information on non-seasonal influenza viruses can be found at: http://who.int/influenza/human_animal_interface/HAI_Risk_Assessment/en/inde.
Countries in the temperate zone of the northern hemisphere
influenza activity in North America remained at low levels throughout
the region. In Canada and the United States of America, influenza
activity remained at interseasonal levels. In Mexico, influenza activity
remained low after a period of 2 months (July-August 2013) with higher
Influenza activity in Europe
remained at interseasonal levels. None of the specimens collected from
sentinel sites between 10-22 Sep 2013 tested positive for influenza.
However, many countries started reporting increased consultation rates
for influenza-like illness (ILI) and acute respiratory infection (ARI).
Northern Africa and the Western Asia region
activity was low in the Northern Africa and western Asia regions. Only
Qatar reported influenza activity, mainly influenza A virus (not
subtyped), since the end of August 2013.
activity in the temperate region of Asia remained at interseasonal
levels since late May 2013. In Mongolia, clinical activity started to
increase since mid-August 2013, but no influenza viruses were detected
in this period.
Countries in the tropical zone
Tropical countries of the Americas/Central America and the Caribbean:
influenza activity in the Caribbean and Central America was at a low
level throughout the region. Decreasing numbers of influenza A virus
have been seen throughout the region, but influenza transmission had
largely come to an end in the last few weeks in these countries.
Co-circulation of influenza A(H3N2) and influenza B viruses were
reported, and RSV predominated among respiratory viruses in Costa Rica,
El Salvador, Nicaragua, and Panama.
In tropical South America,
respiratory virus activity continued decreasing following a period of
high influenza activity in July and August 2013. In Colombia, the
proportions of outpatient visits, hospitalizations, and ICU admissions
were similar to reports for the same period in previous years. In
Venezuela, ARI and pneumonia levels were reported within the expected
values for the time of year. In Ecuador, the number of positive
influenza samples steadily decreased since its influenza peak in August
2013. In Peru, reports of ARI in children under 5 years of age have been
increasing since July 2013, but were consistent with levels from
previous years. In the Plurinational State of Bolivia, the proportion of
SARI-related hospitalizations were reported as elevated compared to the
data from the same period last year , and laboratory data from
CENETROP [National Center of Tropical and Infectious Diseases] in Santa
Cruz showed that of 182 SARI samples analyzed in the beginning of
October 2013, 33 percent were positive for a respiratory virus (a 9
percent increase from the previous week). Brazil showed a continuing
decline in the number of positive influenza samples since July 2013, and
among recent positive samples, influenza A un-typed and influenza B
viruses were detected.
Central African tropical region
d'Ivoire, Ghana, and Kenya reported circulating influenza viruses. In
Cote d'Ivoire and Ghana, influenza B and A(H3N2) were the predominant
viruses detected. Kenya reported low influenza activity due to both
influenza A(H3N2) and influenza B viruses.
transmission in southern and Southeast Asia was low in most countries.
Both influenza A(H1N1)pdm09 and A(H3N2) viruses were reported in this
area. Since early July 2013, an increase in influenza transmission was
seen in Hong Kong Special Administrative Region (SAR), China. The
influenza transmission in Hong Kong SAR was predominated by influenza
A(H3N2) virus. This increased transmission was also seen in the
influenza associated hospital rates in this region; mainly the rates
among 0-4-year-old patients increased over the past month. In the south
of China, influenza activity remained at an interseasonal level.
However, the number of influenza virus detections has been higher in
this year's  interseasonal period compared to the previous year.
Countries in the temperate zone of the southern hemisphere
Temperate countries of South America
the temperate countries of South America, ARI activity was reported at
expected levels for the time of year, and RSV continued to be the most
common respiratory virus detected in Argentina and Chile, although cases
had largely decreased. In Argentina, ILI activity continued its
decreasing trend since its peak in June and July of this year . In
Chile, the proportion of SARI-associated hospitalizations continued to
decrease. In Paraguay, the ILI consultation rate was higher than
expected for the time of year but with decreased influenza and
respiratory virus detection. In Uruguay, the proportion of
SARI-associated hospitalizations increased from levels reported in the
previous week, but proportions of ICU admissions continued to decline.
Temperate countries of Southern Africa
a peak in influenza activity in South Africa due to influenza
A(H1N1)pmd09 in June 2013, a small 2nd peak was observed in the last few
weeks due to increased influenza A(H3N2) and influenza B circulation.
Overall, in Australia, New Zealand, and the Pacific Islands, influenza activity seemed to have peaked.
Australia, during the period from 30 Aug to 13 Sep 2013, the
distribution of influenza types and subtypes was variable across
jurisdictions. In Western Australia, influenza A(H3N2) remained the
predominant virus subtype; however, the proportion of A(H1N1)pdm09
increased. Influenza type B continued to represent over half of
Victoria's influenza notifications. In recent weeks, there have been
increasing proportions of influenza B virus in Queensland and South
Australia. Influenza positivity levels ranged from 15 percent (309/2114)
in the national sentinel laboratory surveillance to 28.1 percent
(56/199) in the Australian Sentinel Practices Research Network (ASPREN).
The Influenza Complications Alert Network (FluCAN) sentinel hospital
surveillance system reported that the rate of influenza associated
hospitalisations had been relatively stable since mid-August 2013.
Almost 15 percent of influenza associated hospitalisations were admitted
directly to the ICU. The age distribution of hospital admissions showed
peaks in the 0-9 and over 60 years age groups.
In New Zealand,
ILI activity was almost at the baseline threshold in early September
2013 but decreased since then. Out of 303 samples received in the last
week, 161 were positive for influenza (53 percent): 49 were influenza B,
16 were influenza A(H3N2), 22 were influenza A(H1N1)pdm09, and 74 were
influenza A (not subtyped). In Auckland and Counties Manukau District
Health Boards, decreased influenza activity was reported in community
surveillance and hospital surveillance.