Clinical Updates
8 June 2009
Swine influenza in humans: Update 12
Current status of the outbreak
Cases of human infection with the swine-lineage influenza A (H1N1) virus (swine influenza) continue to be identified throughout the world. Seventy-three countries from both the Northern and Southern hemispheres have reported cases [1], see Table listing affected countries, and although human-to-human transmission has now been demonstrated in some countries, including the United Kingdom, the current pandemic influenza alert level remains at phase 5 [2, 3].
Reporting methods relating to cases of swine influenza in humans differs between countries. For example, in the United States the surveillance for swine influenza is now being done through their routine influenza surveillance systems [4] and both confirmed and probable cases are being reported. In Chile, as of 1 June 2009, mild suspected cases are no longer being laboratory confirmed [5], and in Australia a clinical case definition is in use in the state of Victoria, whereas in other states and territories, laboratory confirmation continues [6].
Most confirmed cases have been characterised by an uncomplicated febrile respiratory illness [7, 8]. However, vomiting and diarrhoea have been seen in up to a quarter of patients in the United States, and there has been a three percent hospitalisation rate (in Canada and the US) of persons with more severe symptoms [7-9].
Many reported cases have occurred in younger individuals; the median age in Canada and the US is 17 years, with a similar age distribution of cases in the UK, Chile, Japan and Mexico [9-13]. The younger age of cases may be related to exposure that has occurred during travel or in school settings. However, there is recent information that adults age 60 and older may have some pre-existing antibody to the swine-lineage influenza virus [14]. The implications of this finding are yet to be determined.
The outbreak in Mexico peaked on 27 April 2009 [11]. There has been a decline in cases reported since that time, although there remains ongoing influenza activity. Most deaths from swine influenza virus have been recorded in Mexico; however, deaths have also occurred in the United States, Canada, Chile, Costa Rica and the Dominican Republic. Outside of Mexico, those who have died often have had chronic medical conditions that put them at risk for complications from influenza.
The WHO remains focused on mitigation of the consequences of the outbreak. They do not recommend closure of borders, nor do they recommend travel restrictions, in an effort to prevent disruption to the global community [15]. Nevertheless, they emphasise continued vigilance by all countries as they deal with the potential social and economic consequences caused by influenza [16, 17].
Advice for travellers
There are currently no travel restrictions to any country.
Before you travel
- If you are ill with a respiratory illness you should delay travel.
- Check to see if your destination is reporting cases of swine flu. You can look on the NaTHNaC website for up-to-date case totals: http://www.nathnac.org/pro/swineflu.htm
- You should consider:
- whether you need to go to a swine flu affected area
- the risk of getting swine flu at your destination
- the level of medical care at your destination including access to anti-viral medications in the event you need treatment for an influenza-like illness (ILI) (fever plus two or more of cough, sore throat, runny nose, muscle aches or headache).
- You should receive appropriate vaccines and other preventive measures for your destination. This includes seasonal influenza vaccine if you come under the recommended risk groups (see NaTHNaC Health Information Sheet on Influenza). It is not expected that seasonal influenza vaccine will protect against swine influenza [14].
- You should obtain comprehensive travel health insurance, and clarify if there are any exclusions to coverage
During travel
Influenza is transmitted via the respiratory route and you should exercise sensible precautions:
- follow public health guidance at your destination
- avoid crowding or mass gatherings
- avoid close contact (within 2 meters) with persons who are ill with an ILI
- wash hands with soap and water; use waterless alcohol-based hand gels when soap and water is not available
- avoid touching your nose, mouth or eyes, to prevent the spread of germs
- cover your nose and mouth with a tissue when you cough or sneeze and dispose of the tissue promptly
- keep hard surfaces (e.g. door handles, countertops) clean using a normal cleaning solution
- assure that children follow similar advice
- swine flu is not passed through properly handled and prepared pork; the virus is killed by cooking to temperatures of 70°C
- there is little evidence of the effectiveness of wearing masks at a mass level, however, properly fitted, special grade masks can be worn in situations such as healthcare settings [18]
After you travel
Travellers who have visited affected areas should monitor their health for seven days after the visit. If you develop a febrile illness with cough, sore throat, runny nose, headache or muscle aches, within seven days you should:
- check your symptoms on NHS Direct
- (www.nhsdirect.nhs.uk) or NHS Choices (www.nhs.uk), and if you remain concerned, contact your GP or NHS Direct (0845 4647) and inform them of your travel history
- limit contact with other people
- cover your nose and mouth with a tissue when you cough or sneeze and dispose of the tissue promptly
- wash hands with soap and water
- keep hard surfaces (e.g. door handles, countertops) clean using a normal cleaning solution
- There is guidance for health professionals who evaluate persons with suspected swine influenza on the Health Protection Agency website, listed below.
Further information is available at the following sources:
Foreign and Commonwealth Office. Swine flu outbreak: http://www.fco.gov.uk/en/travelling-and-living-overseas/swine-flu
Health Protection Agency, Swine Influenza: http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebAuto
ListName/Page/1240732817665?p=1240732817665
Health Protection Agency: Algorithm for the management of suspected cases (returning travellers and visitors from countries affected by swine influenza A/H1N1 or contacts). S5. 22 May 2009. [Accessed 8 June 2009]. Available at: http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/12407328
WHO, Influenza A (H1N1): http://www.who.int/csr/disease/swineflu/en/index.html
European Centre for Disease Prevention and Control: http://ecdc.europa.eu/
Centers for Disease Control and Prevention, H1N1 Flu (Swine flu): http://www.cdc.gov/h1n1flu/
NaTHNaC Country Information pages: http://www.nathnac.org/ds/map_world.aspx
NHS Choices: http://www.nhs.uk/Pages/HomePage.aspx
The Lancet: H1N1 Flu Resource Centre: http://www.thelancet.com/H1N1-flu
References
1. World Health Organization. Influenza A (H1N1) – update 45. 8 June 2009. [Accessed 8 June 2009]. Available at: http://www.who.int/csr/don/2009_06_08/en/index.html
2. World Health Organization. Current WHO phase of pandemic alert. [Accessed 5 June 2009]. Available at: http://www.who.int/csr/disease/avian_influenza/phase/en/index.
3. World Health Organization. Third meeting of the IHR emergency committee. [Accessed 8 June 2009]. Available at: http://www.who.int/csr/disease/swineflu/3rd_meeting_ihr/en/ind
4. Centers for Disease Control and Prevention. Flu Activity & Surveillance. [Accessed 8 June 2009]. Available at: http://www.cdc.gov/flu/weekly/fluactivity.htm
5. Ministerio de Salud de Chile. Guía clínica para el manejo de casos Nueva Influenza Humana A (H1N1) (IHA H1N1), Etapa de Mitigación, 29 May 2009. [Accessed 8 June 2009]. Available at: http://www.redsalud.gov.cl/portal/url/item/6b14a541236acdeae0
6. Australian Government. H1N1 09 Outbreak, 8 June 2009. [Accessed 8 June 2009]. Available at: http://www.healthemergency.gov.au/internet/healthemergency/pu
blishing.nsf/Content/health-swine_influenza-index.htm#update8june
7. Novel swine-origin influenza A (H1N1) virus investigation team. Emergence of a novel swine-origin influenza A (H1N1) virus in humans. N Engl J Med. 361: 7 May 2009 (10.1056/NEJMoa0903810) Available at: http://content.nejm.org/cgi/content/full/NEJMoa0903810
8. Centers for Disease Control and Prevention. Update: Novel influenza A (H1N1) virus infections – Worldwide, May 6, 2009. MMWR. 58:453-458, 2009. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5817a1.htm
9. Centers for Disease Control and Prevention. Hospitalized patients with novel influenza A (H1N1) virus infection – California, April-May, 2009. MMWR. 58:536-541, 2009. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5819a6.htm
10. Health Protection Agency. Swine-lineage influenza A H1N1. UK update. 4 June 2009. [Accessed 8 June 2009]. Available at: http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1244100063
11. Secretaría de salud, Mexico. Situación actual de la epidemia. 4 June 2009. [Accessed 8 June 2009]. Available at: http://portal.salud.gob.mx/sites/salud/descargas/pdf/influenza/si
tuacion_actual_epidemia_040609.pdf
12. Nishiura et al, 2009. Transmission potential of the new influenza A (H1N1) virus and its age-specificity in Japan. Eurosurveillance. 14: 22. Available at: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19227
13. Ministerio de Salud de Chile. Descripción de la situación de Influenza A/H1N1 en Chile, 2 June 2009. [Accessed 8 June 2009]. Available at: http://www.redsalud.gov.cl/portal/url/item/6b8588c6158c7a3de0
14. Centers for Disease Control and Prevention. Serum-cross-reactive antibody response to a novel influenza A (H1N1) virus after vaccination with d=seasonal influenza vaccine. MMWR 58:521-524. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5819a1.htm
15. World Health Organization. No rationale for travel restrictions. 1 May 2009 [Accessed 29 May 2009]. Available at: http://www.who.int/csr/disease/swineflu/guidance/public_
health/travel_advice/en/index.html
16. World Health Organization. Assessing the severity of an influenza pandemic. 11 May 2009. [Accessed 29 May 2009]. Available at: http://www.who.int/csr/disease/swineflu/assess/disease_
swineflu_assess_20090511/en/index.html
17. World Health Organization. Summary of a high-level consultation: new influenza A (H1N1). 18 May 2009. [Accessed 29 May 2009]. Available at: http://www.who.int/csr/resources/publications/swineflu/
technical_consultation_summaryreport2009_05_18/en/index
18. World Health Organization. Advice on the use of masks in the community setting in influenza A (H1N1) outbreaks. Interim guidance. 3 May 2009. [Accessed 15 May 2009]. Available at: http://www.who.int/csr/resources/publications/swineflu/masks
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