27 August 2009

Pandemic (H1N1) 2009 influenza: Update 18: Current status of the pandemic

Pandemic influenza has affected 177 countries from all World Health Organization (WHO) Regions; more than 182,000 cases have been reported [1]. Many countries are no longer testing and reporting individual cases, so the global case total significantly underestimates the actual number that has occurred.

Countries with widespread community transmission of pandemic influenza are focusing on trends and intensity of respiratory illness, hospitalisations and deaths from pneumonia and influenza, and monitoring virus for changes in type or drug resistance [2, 3].

Global pandemic influenza trends are being summarised by the WHO and European trends by the European Centre for Prevention and Disease Control. An analysis of global trends of illness from early August 2009 found that there were declining numbers of cases in temperate countries of the Northern Hemisphere, including North America and Europe [1, 4, 5]. However, most countries were still experiencing pandemic influenza activity, and increased activity was occurring in newly affected areas. In Mexico the first peak of cases occurred the week of 23 April 2009, with a second peak the week of 25 June [6].

Countries in the Southern Hemisphere that are now emerging from their winter season are generally experiencing a decline in pandemic influenza activity. The exception is South Africa which was affected by the pandemic later than other countries in the Southern Hemisphere. Tropical countries of Asia are reporting increasing rates of illness.

In the Southern Hemisphere, pandemic (H1N1) 2009 virus has replaced seasonal influenza viruses as the predominant strain; about 90% of influenza virus isolates are the pandemic virus [7]. In the Northern Hemisphere 68% to 75% of influenza isolates have been the pandemic virus. It seems likely that pandemic (H1N1) 2009 virus will be the dominant virus during the early months of the winter influenza season.

Twelve oseltamivir-resistant viruses have been detected: four from Japan, two from the USA and Hong Kong, and one each from Canada, China, Denmark, and Singapore [1]. These isolates remain sensitive to the other neuraminidase inhibitor, zanamivir. There is no evidence that there has been a change in ability of the pandemic virus to spread or cause severe disease.

Many countries are now reviewing implementation plans for monovalent pandemic (H1N1) 2009 influenza virus vaccine [8-10]. Considerations of vaccine safety, target populations and surveillance for adverse events following vaccination are being debated.      

Advice for travellers

Travellers need to be aware that some countries have put into place health screening of arriving passengers [11, 12]. Travellers can check the country pages of the Foreign and Commonwealth Office for specific information, or the website of the International Air Transport Association. 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 influenza-like illness (ILI) (fever plus two or more of the following: cough, sore throat, runny nose, body aches, headache, and fatigue) 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.

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.

The current pandemic alert level is at phase 6, indicating widespread global transmission. Consistent with this, the WHO do not recommend closure of borders, nor do they recommend international travel restrictions.

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 (Swine 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)_Outbreak.aspx

Foreign and Commonwealth Office. Swine flu outbreak: http://www.fco.gov.uk/en/travelling-and-living-overseas/swine-flu

Health Protection Agency, Swine Influenza (influenza A H1N1v): http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebAuto

ListName/Page/1240732817665?p=1240732817665

International Air Transport Association. Influenza A(H1N1) - measures adopted by governments worldwide: http://www.iata.org/whatwedo/safety_security/

safety/health_safety/measures.htm

National Pandemic Flu Service: http://www.direct.gov.uk/pandemicflu

NHS Choices: http://www.nhs.uk/Pages/HomePage.aspx 

WHO, Pandemic (H1N1) 2009: http://www.who.int/csr/disease/swineflu/en/index.html

References

1. World Health Organization. Pandemic (H1N1) 2009 - update 62.

Laboratory-confirmed cases of pandemic (H1N1) 2009 as officially reported to WHO by States Parties to the IHR (2005) as of 13 August 2009. 21 August 2009. [Accessed 27 August 2009]. Available at: http://www.who.int/csr/don/2009_08_21/en/index.html

2. World Health Organization. Pandemic (H1N1) 2009 briefing note 3 (revised). Changes in reporting requirements for pandemic (H1N1) 2009 virus infection. 16 July 2009. [Accessed 27 August 2009]. Available at: http://www.who.int/csr/disease/swineflu/notes/

h1n1_surveillance_20090710/en/index.html

3. Centers for Disease Control and Prevention. H1N1 monitoring. Questions and answers. [Accessed 27 August 2009]. Available at: http://www.cdc.gov/h1n1flu/reportingqa.htm

4. European Centre for Prevention and Disease Control. ECDC daily update. Pandemic (H1N1) 2009. 26 August 2009. [Accessed 27 August 2009]. Available at: http://ecdc.europa.eu/en/healthtopics/Documents/

090826_Influenza_AH1N1_Situation_Report_1700hrs.pdf

5. Centers for Disease Control and Prevention. Key flu indicators. 26 August 2009. [Accessed 27 August 32009]. Available at: http://www.cdc.gov/h1n1flu/ 

6. Secretaría de Salud, Mexico. Situación actual de la epidemia. 20 August 2009. [Accessed 27 August 2009]. Available at: http://portal.salud.gob.mx/redirector?tipo=

0&n_seccion=Boletines&seccion=2009-08-25_4112.html

7. World Health Organization. FluNet Global Data (week 17-32). 21 August 2009. [Accessed 26 August 2009]. Available at: http://www.who.int/csr/don/Virologicaldata2009_08_21.pdf

8. World Health Organization. WHO recommendations on pandemic (H1N1) 2009 vaccines. Pandemic (H1N1) 2009 briefing note 2. 13 July 2009. [Accessed 27 August 2009]. Available at: http://www.who.int/csr/disease/swineflu/notes/

h1n1_vaccine_20090713/en/index.html

9. European Centre for Prevention and Disease Control. ECDC Interim Guidance. Use of specific pandemic influenza vaccines during the H1N1 2009 pandemic. August 2009. [Accessed 27 August 2009]. Available at: http://ecdc.europa.eu/en/publications/Publications/

Forms/ECDC_DispForm.aspx?ID=388

10. National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention. Use of Influenza A (H1N1) 2009 Monovalent Vaccine. Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. 21 August 2009. MMWR 58(early release):1-8. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/rr58e0821a1.htm

11. Centers for Disease Control and Prevention. Possible novel H1N1 flu screening for international travellers. 14 July 2009. [Accessed 27 August 2009]. Available at: http://wwwn.cdc.gov/travel/content/news-announcements/delays-H1N1-screening.aspx  

12. NaTHNaC. Pandemic (H1N1) 2009 influenza: Update 16: Potential health screening of international travellers. 20 July 2009. [Accessed 27 August 2009]. Available at: http://www.nathnac.org/pro/clinical_updates/flu_200709.htm