swine flu
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Etiology
Epidemiology
- outbreak of swine flu in April of 2009 in the US & Mexico; outbreak with features of global pandemic; spread to southern hemisphere June 2009[5]
- 1/3 of elderly (> 60 years of age) show an immune response to H1N1 virus, suggesting previous exposure to an antigenically similar virus[3]
- the swine flu of 2009 is transmitted between humans; not clear how it is transmitted or how in contagious it is; transmission by aerosol or by skin-to-skin contact suspected
- swine flu not transmitted by eating pork
- patients considered contagious until at least 7 days after the onset of symptoms
- in the fall of 2009, 97% of the influenza A viruses circulating in the USA are the novel H1N1 virus
- as of 11:00 AM ET on July 24, 2009, CDC reported 43,771 confirmed & probable cases & 302 deaths in 50 states, 4 territories & the District of Columbia:
- median age of hospitalized cases 27 years[20]
- hospitalization rates highest among infants < 1 year & lowest among elderly
- fatality rates of hospitalized patients 11% overall, highest among those > 50 years & lowest in children < 18 years
- 2/3 of fatalities in hospitalized patients had underlying medical conditions associated with severe disease, & > 1/2 were obese[20]
- person-to-person transmission of H3N2 virus Nov 2011[27]
- swine flu capable of infecting humans found in China 2020[28]
Pathology
- an inflammatory response might be responsible for high mortality from H1N1 influenza in young, otherwise healthy patients with strong immune systems who experience a cytokine storm[23]
Genetics
- the virus of the 2009 outbreak contains a combination of swine, avian, & human influenza virus genes
Clinical manifestations
- similar to annual influenza (see influenza)
- fever, myalgias, rhinorrhea, & sore throat
- nausea, vomiting, & diarrhea may be more common with the 2009 swine flu than with annual flu
- signs of severe disease in infected children include: apnea, tachypnea, dyspnea, cyanosis, dehydration, altered mental status, & extreme irritability, seizures[8]
Diagnostic criteria
- acute febrile respiratory illness
- temperature >= 100.4 degrees
- recent onset of one of the following: rhinorrhea, nasal congestion, sore throat, or cough
- confirmation requires identification by PCR or viral culture
- suspected cases include symptomatic patients with recent (within 7 days) travel to infected areas or contact with a known case
Laboratory
- nasopharyngeal swab specimen
- rRT-PCR Swine Flu Panel
- viral culture
- cases are confirmed by PCR or viral culture
- probable cases include those positive for influenza A, but negative for H1 & H3 by PCR
- rapid diagnostic tests have low sensitivity[12]
- overall sensitivity for novel influenza A 40-69%
- for high viral titers by PCR sensitivity 89-100%
- tests are generally more sensitive for seasonal flu (60-83%) than for novel influenza A
Complications
- 150 deaths in Mexico from the 2009 outbreak; many of the deaths occurred in young healthy persons
- obesity seems to be a risk factor for severe disease & mortality
- bacterial coinfection (mostly Streptococcus pneumonia) a factor in H1N1 virus-related deaths[14]
- children with preexisting chronic medical condition or coinfection with MRSA pneumonia at increased risk of death[26]
Management
- Treatment:
- the 2009 swine flu is
- sensitive to oseltamivir (Tamiflu) & zanamivir (Relenza)
- H1N1 strains resistant to oseltamivir (Tamiflu) have been reported
- use of zanamivir (Relenza) or oseltamivir (Tamiflu) in combination with rimantadine recommended[18]
- resistant to amantadine & rimantadine
- cases of oseltamivir (Tamiflu) have been reported[7]
- sensitive to oseltamivir (Tamiflu) & zanamivir (Relenza)
- by analogy, treatment likely most effective if given within two days of the onset of symptoms
- patients may still benefit if treatment is started later[21]
- pregnant women & other high-risk individials suspected of being infected should receive empiric antiviral treatment[11][21][24]
- even those without risk factors might benefit[21]
- IV peramivir (investigational drug) for emergency use[19]
- glucocorticoids mitigate the inflammatory response in severely ill patients
- maxingshigan-yinqiaosan may be as effective as oseltamivir
- the 2009 swine flu is
- Prevention:
- influenza A H1N1 monovalent vaccine available Oct 2009
- pregnant women
- household contacts of infants under 6 months
- healthcare & emergency-services workers
- young people between 6 months & 24 years of age
- nonelderly adults with underlying risk conditions such as diabetes & chronic lung disease
- people over 65 have the lowest priority
- 2009 seasonal flu vaccine may provide some protection[17]
- surgical mask as effective as N95 respirator[15][22] for those in direct contact with infected individuals
- people who are sick are urged to stay home from work or school & to avoid contact with others, except to seek medical care
- local schools were closed for 2 weeks if a student was confirmed to have swine flu
- students with symptoms of flu should stay home for 1 week[2]
- influenza A H1N1 monovalent vaccine available Oct 2009
More general terms
Additional terms
- influenza A (H1N1) monovalent vaccine
- influenza A H1N1 virus (swine flu virus, Spanish flu virus)
- rRT-PCR Swine Flu Panel; influenza A H1N1 rRT-PCR
References
- ↑ Swine Influenza (Flu) Centers for Disease Control http://www.cdc.gov/swineflu/
- ↑ 2.0 2.1 Centers for Disease Control and Prevention (CDC). Update: Infections with a swine-origin influenza A (H1N1) virus - United States and other countries, April 28, 2009. MMWR Morb Mortal Wkly Rep 2009 Apr 28; 58d:1. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0428a2.htm
Centers for Disease Control and Prevention (CDC). Update: Drug susceptibility of swine-origin influenza A (H1N1) viruses, April 2009. MMWR Morb Mortal Wkly Rep 2009 Apr 28; 58d:1. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0428a1.htm
FDA authorizes emergency use of influenza medicines, diagnostic test in response to swine flu outbreak in humans [press release]. Rockville, MD: Food and Drug Administration; Apr 27 , 2009. http://www.fda.gov/bbs/topics/NEWS/2009/NEW02002.html
Statement by HHS Secretary Kathleen Sebelius and by Acting CDC Director Dr. Richard Besser Regarding the Change in CDC's School and Child Care Closure Guidance Tuesday, May 5, 2009 http://www.hhs.gov/news/press/2009pres/05/20090505a.html - ↑ 3.0 3.1 Serum Cross-Reactive Antibody Response to a Novel Influenza A (H1N1) Virus After Vaccination with Seasonal Influenza Vaccine MMWR May 22, 2009 / 58(19);521-524 http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5819a1.htm
- ↑ Prescriber's Letter 16(6): 2009 H1N1 Flu (Swine Flu) PATIENT HANDOUT: H1N1 Flu (Swine Flu) PDF: Interim Guidance on Antiviral Recommendations for H1N1 Flu Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=250602&pb=PRL (subscription needed) http://www.prescribersletter.com
- ↑ 5.0 5.1 CDC Telebriefing on Investigation of Human Cases of Novel Influenza A (H1N1); June 26, 2009, 1 p.m. ET http://www.cdc.gov/media/transcripts/2009/t090626.htm
- ↑ Napolitano LM et al Intensive-Care Patients With Severe Novel Influenza A (H1N1) Virus Infection --- Michigan, June 2009 MMWR July 10, 2009 / 58(Dispatch);1-4 Not yet indexed http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0710a1.htm
- ↑ 7.0 7.1 Centers for Disease Control and Prevention CDC Health Alert Network (HAN) Info Service Message: Three Reports of Oseltamivir Resistant Novel Influenza A (H1N1) Viruses http://www.cdc.gov/h1n1flu/HAN/070909.htm
- ↑ 8.0 8.1 Evans AS et al Neurologic Complications Associated with Novel Influenza A (H1N1) Virus Infection in Children - Dallas, Texas, May 2009 MMWR July 24, 2009 / 58(28);773-778 http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5828a2.htm
- ↑ N Eng J Med H1N1 Influenza Center http://h1n1.nejm.org/
- ↑ Prescriber's Letter 16(8): 2009 CHART: Disaster-Relief and Pandemic-Related Resources COMMENTARY: Infection Control with H1N1 Flu in the Patient Care Setting PDF: Interim Guidance on Antiviral Recommendations for H1N1 Flu Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=250809&pb=PRL
- ↑ 11.0 11.1 Jamieson DJ et al H1N1 2009 influenza virus infection during pregnancy in the USA Lancet, Early Online Publication, 29 July 2009 PMID: https://www.ncbi.nlm.nih.gov/pubmed/19643469 doi:10.1016/S0140-6736(09)61304-0 Centers for Disease Control and Prevention Press Release: July 29, 2009 CDC Advisors Make Recommendations for Use of Vaccine Against Novel H1N1
- ↑ 12.0 12.1 Balish A Evaluation of Rapid Influenza Diagnostic Tests for Detection of Novel Influenza A (H1N1) Virus - United States, 2009 MMWR August 7, 2009 / 58(30);826-829
- ↑ Prescriber's Letter 16(10): 2009 COMMENTARY: The 2009 H1N1 Influenza Virus Vaccine PDF: Interim Recommendations for the Use of Antiviral Medications for Influenza (2009-2010 Season) PDF: Tamiflu Suspension: Potential Medication Errors COMMENTARY: Recommendations from the CDC for Use of Influenza A (H1N1) 2009 Monovalent Vaccine Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=251025&pb=PRL (subscription needed) http://www.prescribersletter.com
- ↑ 14.0 14.1 Centers for Disease Control September 29, 2009, 58:1-4 Bacterial Coinfections in Lung Tissue Specimens from Fatal Cases of 2009 Pandemic Influenza A (H1N1) - United States, May-August 2009 http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58e0929a1.htm
Centers for Disease Control Interim guidance for use of 23-valent pneumococcal polysaccharide vaccine during novel influenza A (H1N1) outbreak. June 9, 2009 http://www.cdc.gov/h1n1flu/guidance/ppsv_h1n1.htm - ↑ 15.0 15.1 Loeb M et al Surgical Mask vs N95 Respirator for Preventing Influenza Among Health Care Workers JAMA. 2009;302(17) doi:10.1001/jama.2009.1466
Srinivasan A and Perl TM Respiratory Protection Against Influenza JAMA. 2009;302(17) doi:10.1001/jama.2009.1494 - ↑ Centers for Disease Control and Prevention Press Briefing Transcripts Weekly 2009 H1N1 Flu Media Briefing http://www.cdc.gov/media/transcripts/2009/t091001.htm
- ↑ 17.0 17.1 Garcia-Garcia L et al Partial protection of seasonal trivalent inactivated vaccine against novel pandemic influenza A/H1N1 2009: case-control study in Mexico City BMJ 2009;339:b3928 PMID: https://www.ncbi.nlm.nih.gov/pubmed/19808768 doi:10.1136/bmj.b3928 http://www.bmj.com/cgi/content/full/339/oct06_2/b3928
- ↑ 18.0 18.1 Prescriber's Letter 16(2): 2009 CDC's Interim Influenza Antiviral Guidance for 2008-09 Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=250201&pb=PRL (subscription needed) http://www.prescribersletter.com
- ↑ 19.0 19.1 FDA MedWatch http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm187814.htm
- ↑ 20.0 20.1 20.2 Louie JK et al Factors Associated With Death or Hospitalization Due to Pandemic 2009 Influenza A(H1N1) Infection in California JAMA. 2009;302(17):1896-1902 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/19887665 <Internet> http://jama.ama-assn.org/cgi/content/short/302/17/1896
- ↑ 21.0 21.1 21.2 21.3 Quick Facts for Clinicians on Antiviral Treatments for 2009 H1N1: Centers for Disease Control and Prevention (CDC) http://www.cdc.gov/H1N1flu/antivirals/facts_clinicians.htm
- ↑ 22.0 22.1 Gralton J and McLaws M-L Protecting healthcare workers from pandemic influenza: N95 or surgical masks: Crit Care Med 2009, Sept 1 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/20095070 <Internet> http://tinyurl.com/yztbnke
- ↑ 23.0 23.1 Quispe-Laime AM et al. H1N1 influenza A virus-associated acute lung injury: Response to combination oseltamivir and prolonged corticosteroid treatment. Intensive Care Med 2009 Nov 19; <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/19924393 <Internet> http://dx.doi.org/10.1007/s00134-009-1727-6
- ↑ 24.0 24.1 Centers for Disease Control and Prevention Maternal and Infant Outcomes Among Severely Ill Pregnant and Postpartum Women with 2009 Pandemic Influenza A (H1N1)
United States, April 2009--August 2010 Morbidity and Mortality Weekly Report (MMWR) September 9, 2011 / 60(35);1193-1196 http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6035a2.htm - ↑ Noah MA et al. Referral to an extracorporeal membrane oxygenation center and mortality among patients with severe 2009 influenza A (H1N1). JAMA 2011 Oct 19; 306:1659 PMID: https://www.ncbi.nlm.nih.gov/pubmed/21976615
- ↑ 26.0 26.1 Randolph AG et al. Critically ill children during the 2009-2010 influenza pandemic in the United States. Pediatrics 2011 Dec; 128:e1 PMID: https://www.ncbi.nlm.nih.gov/pubmed/22065262
- ↑ 27.0 27.1 Centers for Disease Control and Prevention (CDC). Limited human-to-human transmission of novel influenza A (H3N2) virus - Iowa, November 2011. MMWR Morb Mortal Wkly Rep 2011 Nov 23; 60:1. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm60d1123a1.htm
- ↑ 28.0 28.1 Sun H, Xiao Y, Liu J et al Prevalent Eurasian avian-like H1N1 swine influenza virus with 2009 pandemic viral genes facilitating human infection. Proc Natl Acd Sci USA, June 29, 2020 PMID: https://www.ncbi.nlm.nih.gov/pubmed/32601207 https://www.pnas.org/content/early/2020/06/23/1921186117