Clinical Updates
27 November 2009
Pandemic (H1N1) 2009 influenza: Update 21: Current status of the pandemic
The World Health Organization (WHO) reports that as of 22 November 2009, more than 620,000 confirmed cases of pandemic influenza (H1N1) 2009 have occurred, with more than 7,800 deaths from 207 countries and territories [1]. The European Centre for Disease Prevention and Control (ECDC) produces a map of countries affected by pandemic influenza and the number of fatal cases in their daily pandemic update, which is available on their Pandemic (H1N1) 2009 website page. However, as most countries have stopped counting individual cases, confirmed cases represent a significant underestimate of the actual number of cases. For example, the US Centers for Disease Control and Prevention (CDC) estimated that for every confirmed case of pandemic H1N1 2009 influenza reported from April – July 2009, there were 78 other cases, and for every confirmed hospitalised case there were another 1.7 cases [2]. Extrapolating to mid-October the CDC estimated that 22 million cases, 98,000 hospitalisations and 3,900 deaths occurred in the United Sates [3].
In temperate countries of the northern hemisphere, rates of influenza-like illness (ILI) (fever and two or more of: cough, sore throat, runny nose, body aches, or headache) increased through October, indicating an early start to the winter influenza season [1]. Although activity remains widespread, there is evidence from North America, the Caribbean and a limited number of European countries that transmission may have peaked. For other countries ILI rates continue to increase, and the Ukraine reported a large increase in cases in late October through mid-November [4].
In East Asia, transmission remains active, and in South Asia, ILI activity has increased. In tropical Asia and the Americas transmission intensity is variable, but declining in many countries of Central and South America. There is little activity in the temperate regions of the southern hemisphere.
Pandemic influenza viruses
In the most recent reporting period (8-14 November 2009), 89% of influenza viruses reported via the Global Influenza Surveillance Network were pandemic (H1N1) 2009 virus [5], and in Europe nearly all of the type A influenza viruses are pandemic (H1N1) 2009 virus.
Pandemic viruses that are currently being isolated, with rare exception, remain antigenically and genetically similar to the original isolate: A/California/7/2009, which is the virus used in pandemic vaccines. In Norway, as well as sporadic cases in several other countries, a viral mutation was detected in three isolates [6]. Although these three isolates were associated with severe and fatal illness, mutations have also been detected in mild cases, and the isolates have remained sensitive to oseltamivir and zanamivir. There is no evidence that this mutation is widespread in Norway or in other countries.
Oseltamivir resistance continues to be reported, and as of 27 November 2009, there have been 75 resistant specimens [5, 7]. A few clusters of resistant virus isolates have been reported, including one cluster from the UK, where there was possible transmission between cases [8]. There has been no sustained transmission of these resistant isolates. Empiric treatment recommendations with oseltamivir have not changed.
There is evidence of transmission of pandemic (H1N1) 2009 influenza virus to different species of susceptible animals, e.g. pig, turkey, ferret and cat [9]. It is most likely that these transmissions occurred from infected humans to the animals. There is no evidence that these events impact on the dynamic of the pandemic where human to human transmission readily occurs.
Vaccination
Worldwide, vaccination campaigns are well underway. The WHO estimates that 65 million people have been vaccinated as of 19 November [10]. Common side effects of inactivated injectable vaccines are swelling, redness and pain at the injection site that resolve spontaneously over a short period. Mild systemic symptoms of fever, headache and fatigue are also reported, but these resolve by about 48 hours. There is no evidence of an increased association with Guillain Barré syndrome following pandemic (H1N1) 2009 vaccine. Health Canada have reported 36 cases of severe adverse events amongst 6.6 million doses of vaccine, from 21 October to 7 November [11]. These have included febrile seizures (a seizure brought on by high fever) and anaphylaxis. As a precautionary measure while these are investigated, GlaxoSmithKline has put on hold a vaccine lot of Arepanrix™ associated with a higher rate of anaphylaxis[12].
The Health Protection Agency has published a review of the first phase of the pandemic in England [13], and the WHO have updated their guidance for treatment [14].
Advice for travellers
Travellers need to be aware that some countries have put into place health screening of arriving passengers [15, 16]. Travellers should check with their tour operator, and they can consult the country pages of the Foreign and Commonwealth Office for specific information. Travellers should obtain travel insurance that covers trip cancellation and any potential disruptions to their trip, such as quarantine.
Those who are ill with an ILI should delay their travel, and seek medical advice. The Department of Health launched the National Pandemic Flu Service on 23 July 2009. Travellers can consult this service for guidance on managing an ILI, however, if they have serious underlying health conditions, are pregnant, or are calling about children under one year of age, they should contact their GP directly.
Travellers who fall in the clinical risk groups for seasonal influenza and pandemic (H1N1) 2009 influenza should receive vaccination prior to travel [17].
Further advice on the prevention of pandemic influenza during travel can be found on the NaTHNaC Health Information Sheet: Pandemic (H1N1) 2009 influenza: Advice for travellers.
Further information is available at the following sources:
NaTHNaC Country Information pages: http://www.nathnac.org/ds/map_world.aspx
NaTHNaC Outbreak Surveillance Database: http://www.nathnac.org/countrysearch.aspx
Centers for Disease Control and Prevention. 2009 H1N1 Flu: http://www.cdc.gov/h1n1flu/
European Centre for Disease Prevention and Control. Pandemic (H1N1) 2009: http://ecdc.europa.eu/en/healthtopics/Pages/Influenza_A(H1N1)
Foreign and Commonwealth Office. Swine flu pandemic: http://www.fco.gov.uk/en/travelling-and-living-overseas/swine-flu
Health Protection Agency. Swine Influenza [Pandemic (H1N1) 2009 influenza]: http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebAutoList
Name/Page/1240732817665?p=1240732817665
National Pandemic Flu Service: http://www.direct.gov.uk/pandemicflu
NHS Choices: http://www.nhs.uk/Pages/HomePage.aspx
World Health Organization. Pandemic (H1N1) 2009: http://www.who.int/csr/disease/swineflu/en/index.html
References
1. World Health Organization. Pandemic (H1N1) 2009 - update 76. 27 November 2009. [Accessed 27 November 2009]. Available at: http://www.who.int/csr/don/2009_11_27a/en/index.html
2. Reed C, Angulo FJ, Swerdlow DL, et al. Estimates of the prevalence of pandemic (H1N1) 2009, United States, April-July 2009. Emerg Infect Dis. 15:2004-2007, 2009. Available at: http://www.cdc.gov/eid/content/15/12/2004.htm
3. Centers for Disease Control and Prevention. CDC estimates of 2009 H1N1 influenza cases, hospitalizations and deaths in the United States. April – October 17, 2009. 12 November 2009. [Accessed 27 November 2009]. Available at: http://www.cdc.gov/h1n1flu/estimates_2009_h1n1.htm
4. World Health Organization. Pandemic (H1N1) 2009, Ukraine. 1 November 2009. [Accessed 27 November 2009]. Available at: http://www.who.int/csr/don/2009_11_01/en/index.html
5. World Health Organization. Weekly update (Virologic surveillance data). 27 November 2009. [Accessed 27 November 2009]. Available at: http://www.who.int/csr/disease/swineflu/laboratory27_11_
6. World Health Organization. Public health significance of virus mutation detected in Norway. Pandemic (H1N1) 2009 briefing note 17. 20 November 2009. [Accessed 27 November 2009] Available at: http://www.who.int/csr/disease/swineflu/notes/briefing_200911
7. World Health Organization. Oseltamivir-resistant pandemic (H1N1) 2009 influenza virus, October 2009. Wkly Epidemiol Rec. 84:453-68, 2009. Available at: http://www.who.int/wer/2009/wer8444/en/index.html
8. Health Protection Agency. HPA weekly national influenza report. 26 November (week 48). [Accessed 27 November 2009]. Available at: http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1259151
9. World Health Organization. Infection of farm animals with the pandemic virus. Pandemic (H1N1) 2009 briefing note 15. 5 November 2009. [Accessed 27 November 2009]. Available at: http://www.who.int/csr/disease/swineflu/notes/briefing_200911
10. World Health Organization. Safety of pandemic vaccine. Pandemic (H1N1) 2009 briefing note 16. 19 November 2009. [Accessed 27 November 2009]. Available at: http://www.who.int/csr/disease/swineflu/notes/briefing_200911
11. Public Health Agency of Canada. FluWatch. November 8 – 14, 2009 (Week 45). 20 November 2009. [Accessed 27 November 200]. Available at: http://www.phac-aspc.gc.ca/fluwatch/09-10/w45_09/index-eng.php
12. GlaxoSmithKline. GSKstatment: voluntary hold of Arepanix (adjuvanated H1N1 pandemic vaccine) lot number A80CA007A in Canada. 24 November 2009. [Accessed 27 November 2009]. Available at: http://www.gsk.com/media/GSK-statement-Arepanrix-Canada-Voluntary-Hold-24_11_09.pdf
13. Health Protection Agency. Pandemic (H1N1) 2009 in England: an overview of initial epidemiologic findings and implications for the second wave. V3. 24 November 2009. [Accessed 27 November 2009]. Available at: http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/125856055
14. World Health Organization. Clinical management of human infection with pandemic (H1N1) 2009: revised guidance. November 2009. [Accessed 27 November 2009]. Available at: http://www.who.int/csr/resources/publications/swineflu/clinical_
15. Centers for Disease Control and Prevention. Possible novel H1N1 flu screening for international travellers. 15 October 2009. [Accessed 27 November 2009]. Available at: http://wwwn.cdc.gov/travel/content/news-announcements/delays-H1N1-screening.aspx
16. NaTHNaC. Pandemic (H1N1) 2009 influenza: Update 16: Potential health screening of international travellers. 20 July 2009. Available at: http://www.nathnac.org/pro/clinical_updates/flu_200709.htm
17. Chief Medical Officer (CMO) letter. Department of Health. The H1N1 swine flu vaccination programme 2009-2010. 15 October 2009. [Accessed 27 November 2009]. Available at: http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets
/@dh/@en/documents/digitalasset/dh_107190.pdf
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