Clinical Updates
23 December 2009
Pandemic (H1N1) 2009 influenza: Update 22: Current status of the pandemic
The World Health Organization (WHO) reports that as of 13 December 2009, more than 208 countries and territories have reported cases of pandemic influenza (H1N1) 2009, with nearly 11,000 deaths [1]. The European Centre for Disease Prevention and Control (ECDC) produces a map of countries affected by pandemic influenza with the number of fatal cases in their daily pandemic update that is available on their website.
In temperate countries of the northern hemisphere, transmission of pandemic influenza virus remains active, but in many countries and regions, particularly North America, disease activity has peaked and is now declining [1]. Most countries in western and northern Europe report declining activity; in parts of central and south-eastern Europe, activity continues to increase. Western and central Asia report active transmission. In east Asia transmission of pandemic influenza appears to be declining, and in south Asia, activity is increasing. There is little activity in the temperate regions of the southern hemisphere.
Mortality in the northern hemisphere due to pandemic influenza is similar to that observed in the southern hemisphere earlier in the year during their winter transmission season. This indicates that the overall severity of the pandemic has not increased over time [1]. An analysis of the mortality from pandemic influenza in England, estimates an overall case fatality ratio of 26 deaths per 100,000 cases (0.026%) [2]. This is lower than estimates from the previous pandemics in the 20th century. Two thirds of those who died had underlying chronic medical conditions, particularly of the respiratory, neurological and cardiac systems. The highest incidence rates for infection were in children and young adults aged five to 24 years, but the highest case fatality rate was in adults aged 65 years and older.
Pandemic influenza viruses
In the most recent reporting period (22 November to 5 December 2009), 92% of influenza viruses reported via the Global Influenza Surveillance Network were pandemic (H1N1) 2009 virus [3]. In Europe and North America, 99% of the type A influenza viruses were the pandemic virus [4].
Oseltamivir resistance continues to be reported, and as of 5 December 2009, there have been 136 resistant isolates [3]. Two hospital clusters of resistant virus have been reported, in the United States and Wales [5]. Both clusters were confined to immunocompromised patients without spread to healthcare workers. Immunocompromised persons can have prolonged virus excretion and may not respond to treatment, predisposing them to the development of resistance. An additional cluster of seven cases occurred amongst otherwise healthy students travelling on a prolonged train journey in Viet Nam [6].
Advice for travellers
Travellers need to be aware that some countries have put into place health screening of arriving passengers [7, 8], although the effectiveness of screening methodologies may be low [9]. Travellers should check with their tour operator, and also 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 unwell with an influenza-like illness (ILI) (fever and two or more of: cough, sore throat, runny nose, body aches, or headache) 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 [10].
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. 2009 influenza A(H1N1) pandemic: http://ecdc.europa.eu/en/healthtopics/Pages/Influenza_A
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&HPAwebAuto
ListName/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 79. 18 December 2009. [Accessed 23 December 2009]. Available at: http://www.who.int/csr/don/2009_12_18a/en/index.html
2. Donaldson LJ, Rutter PD, Ellis BM, et al. Mortality from pandemic A/H1N1 2009 influenza in England: public health surveillance study. Brit Med J. 339:b5213, 2009. Available at: http://www.bmj.com/cgi/content/full/339/dec10_1/b5213
3. World Health Organization. Weekly update (Virologic surveillance data). 18 December 2009. [Accessed 23 December 2009]. Available at: http://www.who.int/csr/disease/swineflu/laboratory18_12_
4. Centers for Disease Control and Prevention. FluView. 2009-2010 influenza season week 49 ending December 12, 2009. [Accessed 23 December 2009]. Available at: http://www.cdc.gov/flu/weekly/
5. World Health Organization. Oseltamivir resistance in immunocompromised hospital patients. Pandemic (H1N1) 2009 briefing note 18. 2 December 2009. [Accessed 23 December 2009]. Available at: http://www.who.int/csr/disease/swineflu/notes/briefing_2009
6. Mai LQ, Wertheim HFL, Duong TN, et al. A community cluster of oseltamivir-resistant cases of 2009 H1N1 influenza. N Engl J Med. 10.1056/NEJMC0910448, 2009. Available at: http://h1n1.nejm.org/?p=1348
7. Centers for Disease Control and Prevention. Possible novel H1N1 flu screening for international travellers. 15 October 2009. [Accessed 23 December 2009]. Available at: http://wwwn.cdc.gov/travel/content/news-announcements/delays-H1N1-screening.aspx
8. 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
9. Mukherjee P, Lim PL, Chow A, et al. Epidemiology of travel-associated pandemic (H1N1) 2009 infection in 116 patients, Singapore. Emerg Infect Dis. January, 2010; [Epub ahead of print]. Available at: http://www.cdc.gov/eid/content/16/1/pdfs/09-1376.pdf
10. Chief Medical Officer (CMO) letter. Department of Health. The H1N1 swine flu vaccination programme 2009-2010. 15 October 2009. [Accessed 23 December 2009]. Available at: http://www.dh.gov.uk/prod_consum_dh/groups/dh_digital
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