Influenza update - 12 August 2011
Update number 140
Table of contents
- Summary
- Countries in the temperate zone of the northern hemisphere
- Countries in the tropical zone
- Countries in the temperate zone of the southern hemisphere
- From the peer-reviewed literature
- Virological surveillance
Summary
• Influenza activity in the temperate regions of the northern hemisphere remains low or undetectable.
• Countries in the tropical zone mostly reported low influenza activity but with some transmission reported in countries of the Americas (Dominican Republic, Colombia, and Brazil), western Africa (Ghana and Cameroon), and southern Asia (India, Bangladesh, Thailand, and Singapore).
• Transmission in South Africa has declined to low levels. In Australia, influenza-like illness (ILI) consultations and laboratory-confirmed cases continue to increase with a mix of influenza A(H1N1)2009 and influenza B, which are unevenly distributed across the country. ILI activity in New Zealand has crossed the national baseline levels and the majority of viruses detected have been influenza B.
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Countries in the temperate zone of the northern hemisphere
The influenza season in the northern hemisphere temperate areas has ended. Nearly all of the countries in this zone reported low or no influenza activity.
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Countries in the tropical zone
In central and tropical South America, a few countries reported low level of co-circulation of influenza A(H1N1)2009, influenza A(H3N2), and influenza type B. In the Dominican Republic, the recently reported transmission of influenza has been decreasing. The percentage of samples testing positive for respiratory viruses is less than previous weeks; influenza B has been the only virus detected this week, though influenza A(H1N1)2009 had been the primary virus in circulation during previous weeks. Sporadic detections of influenza A(H1N1)2009 were reported from Costa Rica, Honduras, and Panama. In Colombia, influenza A(H1N1)2009 continues to be the predominant virus while Brazil has reported co-circulation of influenza A(H1N1)2009 and influenza A(H3N2) with later as predominant virus.
In sub-Saharan Africa, influenza transmission has continued in the west. In Ghana, active transmission of predominantly influenza B appears to be ongoing with much smaller numbers of influenza A(H1N1)2009. Cameroon has also reported increasing levels of influenza type B virus in recent weeks. In Nigeria, circulation of all three types of virus has decreased over the past month. Madagascar has recently reported a secondary rise in H1N1 (2009) detections, following a period of more intense transmission of influenza type B earlier in the year, that now appears to be declining. The country has had continuous detection of influenza virus for the past year with the largest number occurring in late January and early February.
Influenza activity in most of tropical Asia remained low with some notable localized areas of transmission. Moderate numbers of influenza A(H3N2) were reported in Bangladesh, India, Singapore and Thailand along with much smaller numbers of influenza A(H1N1)2009 and influenza type B. In Singapore ILI made up only 2% of polyclinic attendances for acute respiratory illness, which is considered low, however 49% of ILI cases tested positive for influenza virus in the last four weeks. Eighty-three percent of influenza viruses from ILI cases were influenza A(H3N2); influenza A(H1N1)2009 and influenza B accounted for 11% and 6% of positive cases respectively. Vietnam continues to report sustained transmission of influenza A(H1N1)2009.
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Countries in the temperate zone of the southern hemisphere
South America
Only low influenza activity was reported in the temperate regions of South America. Influenza detections have been increasing over the past three to four weeks in Chile, primarily influenza A(H1N1) but ILI activity and consultations for respiratory disease in emergency departments remained at low levels of intensity. No deaths from influenza were reported. In Argentina, influenza virus detections have also increased during the same period of time but remain low and most of the viruses have not yet been subtyped. Of those that have, a mix of influenza A(H3N2) and influenza A(H1N1)2009 have been reported. Rates of ILI, severe acute respiratory infection (SARI), and pneumonia are all at lower levels nationally than reported during the same period of 2010. In Paraguay, the proportion of ILI consultations was similar to the previous week (~7.5%) and the proportion of SARI hospitalizations and the proportion of SARI ICU admissions decreased slightly in the last weeks, remaining below 5% and 15% respectively. In Uruguay percent of SARI hospitalizations has increased but is less than five percent of all hospitalizations. There has been a recent decrease in percent of SARI admissions to intensive care and SARI deaths. Influenza A(H1N1)2009 is the most common influenza virus detected in Uruguay in recent weeks.
Southern Africa
Influenza transmission in South Africa is declining and is now at low levels. The influenza season was dominated by influenza A(H1N1)2009 with smaller numbers of influenza type B.
Australia, New Zealand and South Pacific
ILI consultations have continued to rise nationally in Australia with the highest number of laboratory confirmed notifications of influenza reported in Queensland, New South Wales and South Australia. By 22 July 2011, the National Notifiable Diseases Surveillance System (NNDSS) had reported 10,060 confirmed cases of influenza which is much higher than 1,571 for the same period in 2010. However, this year all states reported higher numbers of cases than usual during the summer months, most notable in Northern Territory and Queensland, and the season has commenced very early. The rate of ILI presentations was 3.0 cases per 1,000 presentations which was slightly higher than the previous week’s rate of 2.5 per 1,000 presentations in New South Wales emergency departments; however, total admissions to critical care units were within the usual range for this time of year in the state. The NNDSS was notified of 7 influenza associated deaths so far this year with 6 of these cases having influenza A(H1N1)2009 and the other case reported as having influenza type A (untyped). Death registration data of up to 8 July 2011, early in the winter influenza season, showed 1.6 pneumonia or influenza associated deaths per 100,000 population in New South Wales, which is below the seasonal threshold of 1.8 per 100,000 NSW population. Between 1 July and 28 July 2011, the Australian Paediatric Surveillance Unit has reported 13 hospitalizations associated with severe influenza complications in children, including 7 intensive care unit admissions. The majority of these hospitalizations were associated with influenza A(H1N1)2009 infection, and of the 8 hospitalizations with data, 4 were noted as having underlying chronic conditions. The virus type detected in Australia has not been uniform across the country. In Queensland and New South Wales, influenza A(H1N1)2009 has been the predominant strain with co-circulation of influenza B while in South Australia, influenza B continues to be predominant strain accounting for 72% of notifications. Laboratory confirmed notifications of influenza are also now increasing in other states.
In New Zealand, the rate of national ILI consultations was 66.1 per 100 000 (261 ILI consultations) and is above the baseline levels. The consultation rates reported nationally this influenza season appear to be comparable to those reported last year, though the season is still quite early. Influenza B virus accounts for the large majority of influenza viruses detected in New Zealand.
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From the peer-reviewed literature
A recent article in the American Journal of Infection Control reports on the efforts of a large urban University hospital in the United States to increase vaccination coverage of health care workers through a mandatory vaccination policy. Previous efforts to increase vaccination through the use of "shot brigades" to vaccinate on site in nursing units along with mandatory declinations had achieved coverage of 51%. The mandatory vaccination policy for health care workers was accompanied by a hand hygiene campaign and kickoff fair to emphasize the importance of both hand hygiene and vaccination in preventing transmission to patients. The fair was used to communicate information and dispel myths about influenza vaccination. Key steps in the success of the program are described in the report (see reference below). Requests for exemptions were considered on a case-by-case basis by an exemption committee. The program ultimately achieved 100% compliance among all hospital staff and absenteeism during influenza season was reduced by 8000 hours compared to the previous year.
Comment: While WHO does not have specific recommendations regarding mandatory vaccination of health care staff, the organization does continue to recommend vaccination of health care providers both to reduce transmission of influenza to individuals with conditions that place them at increased risk of complications and to decrease health care worker absenteeism during times when the need for health care services may be high.
(Reference: Kidd F. et al. From 51% to 100%: Mandatory seasonal influenza vaccination. Am J Infect Control 2011;in press:1-3. doi:10.1016/j.ajic.2011.02.022)
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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 Network) 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.