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swine flu

Etiology: - influenza A H1N1 virus - influenza A H3N2 virus 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] Diagnosis: - 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: 1) Treatment: a) 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] b) by analogy, treatment likely most effective if given within two days of the onset of symptoms c) patients may still benefit if treatment is started later [21] d) pregnant women & other high-risk individials suspected of being infected should receive empiric antiviral treatment [11,21,24] e) even those without risk factors might benefit [21] f) IV peramivir (investigational drug) for emergency use [19] g) glucocorticoids mitigate the inflammatory response in severely ill patients h) maxingshigan-yinqiaosan may be as effective as oseltamivir 2) Prevention: a) 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 b) 2009 seasonal flu vaccine may provide some protection [17] c) surgical mask as effective as N95 respirator [15,22] for those in direct contact with infected individuals d) people who are sick are urged to stay home from work or school & to avoid contact with others, except to seek medical care e) local schools were closed for 2 weeks if a student was confirmed to have swine flu f) students with symptoms of flu should stay home for 1 week [2]

Related

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

General

influenza

References

  1. Swine Influenza (Flu) Centers for Disease Control http://www.cdc.gov/swineflu/
  2. 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. 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
  4. 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#: 250602 (subscription needed) http://www.prescribersletter.com
  5. 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
  6. 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. 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. 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
  9. N Eng J Med H1N1 Influenza Center http://h1n1.nejm.org/
  10. 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#: 250809
  11. Jamieson DJ et al H1N1 2009 influenza virus infection during pregnancy in the USA Lancet, Early Online Publication, 29 July 2009 PMID: 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. 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
  13. 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#: 251025 (subscription needed) http://www.prescribersletter.com
  14. 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. 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
  16. 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. 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: 19808768 doi:10.1136/bmj.b3928 http://www.bmj.com/cgi/content/full/339/oct06_2/b3928
  18. Prescriber's Letter 16(2): 2009 CDC's Interim Influenza Antiviral Guidance for 2008-09 Detail-Document#: 250201 (subscription needed) http://www.prescribersletter.com
  19. FDA MedWatch http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm187814.htm
  20. 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 PMID: 19887665 http://jama.ama-assn.org/cgi/content/short/302/17/1896
  21. 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. Gralton J and McLaws M-L Protecting healthcare workers from pandemic influenza: N95 or surgical masks: Crit Care Med 2009, Sept 1 PMID: 20095070 http://tinyurl.com/yztbnke
  23. 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; PMID: 19924393 http://dx.doi.org/10.1007/s00134-009-1727-6
  24. 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
  25. 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: 21976615
  26. Randolph AG et al. Critically ill children during the 2009-2010 influenza pandemic in the United States. Pediatrics 2011 Dec; 128:e1 PMID: 22065262
  27. 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. 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: 32601207 https://www.pnas.org/content/early/2020/06/23/1921186117