Characteristics and Outcome of Patients with Influenza A (H1N1 ...

Egyptian Journal of Medical Microbiology, January 2010 Vol. 19, No. 1shaped curve previously seen only during the1918 H1N1 Spanish pandemic 20 . Few patientsolder than 60 years were admitted to the ICU. Apotential biological basis for this observation isthat patients in this age group have a crossreactiveantibody to 2009 influenza A (H1N1) atmuch higher rates than younger patients 21 .(H1N1) 2009 influenza A recorded casefatalityrate of approximately 1% yet this maywell be an overestimate, because testing is nolonger being reported in many regions and evenmany cases expected as mild flu withouttesting 22 . The case-fatality rate in previousinfluenza pandemics has varied widely, and allsuch reports may be inaccurate owing todifficulty in assessing the total number ofcases 23 . The Spanish flu of 1918 (H1N1 ) wasreported as causing 50 million deaths in 500million individuals infected (10% case-fatalityrate), while the Hong Kong flu of 1968-1969caused 33000 deaths among 50 million infected(0.1% case fatality rate) 24 . The case-fatality rateof avian influenza A (H5N1) was initiallyreported to be as high as 60% but is more likelyin the range of 14% to 33% 25 .During the 1918 pandemic, a large numberof deaths were associated with bacterialinfection 26 , but concurrent bacterial infectiondoes not appear to be a major contributingfactor to the severity of illness in our patients,possibly in part because most receivedantibiotics before hospitalization. This goes inhand with 9 . Lung damage was most likely dueto the primary effect of infection with influenzavirus. Possible mechanisms of damage includedirect injury to the respiratory epithelium with asecondary cytokine storm 27 . They alsowondered whether patients, especially thosewho died, had viremia, as was reported inassociation with H5N1 infection, a veryaggressive variety of influenza 28,29 . Coinfectionwith other respiratory viruses could also explainthe increased pathogenicity among patients 30 .Oseltamivir (Tamiflu) and zanamivir(Relenza) reduce viral replication and shedding,and may reduce the risk of more severe illness.Their safety in pregnancy has not beeninvestigated, but without treatment there may bea greater risk of death and premature labour 31,32 .Increasing resistance to oseltamivir has beenreported in other strains of currently circulatinginfluenza A viruses and in H1N1, but, as yet,H1N1 influenza 2009 lineage was not able to betransmitted between patients and almost allcases who developed resistance where inpatients with severe underlying diseases 33 .88WHO new guidelines for use of antiviralsin management of cases recommends thathealthy patients with uncomplicated illness neednot to be treated with antiviral world wide, mostpatients fully recovered without any form ofmedical treatment. Oseltamivir should beadministered to children below 5 years of old,pregnant women and patients with underlyingconditions 18 .In conclusion, most cases of H1N1infection were mild and responded well toantiviral treatment and only minor casesprogressed to cause serious illness and death.Future studies should identify predictive factorsfor severe disease and, especially, theeffectiveness of early treatment and protectionoffered by having influenza vaccination.Immediate strategies for containment havebecome the key factor in preventing the spreadof this virus. Drastic and intense precautionarymeasures are needed to make H1N1 containableand preventable. The role of academies,researchers, educators, media, industry, andinternational agencies is crucial to ensure thatpeople get the right information at the right timeso that the outcome can be positive in this timeof global fear and infectious crisis.REFERENCES1. Centers for Disease Control andPrevention (CDC) 2009. Swine influenzaA (H1N1) infection in two children-Southern California, March-April. MMWRMorb. Mortal Wkly Rep., 58(15): 400-402.2. Centers for Disease Control andPrevention (CDC) 2009. Outbreak ofswine-origin influenza A (H1N1) virusinfection- Mexico, March-April 2009.MMWR Morb Mortal Wkly Rep., 58(17):467-470.3. Dawood, F.S., Jain, S. and Finelli, L.2009. Novel Swine-Origin influenza(H1N1) Virus Investigation Team.Emergence of a novel swine origininfluenza A (H1N1) virus in humans. N.Engl. J. Med., 360(25): 2605-2615.4. Chan, M. 2009. World now at the start of2009 influenza pandemic. http://www.who.int/mediacentre/news/statements/2009/h1n1_pandemic_phase6_20090611/en/index.html.5. Clem, A. and Galwankar, S. 2006. Avianinfluenza: Preparing for a pandemic. J.Assoc. Physicians India, 54: 563-70.6. Galwantar, S. and Clem, A., 2009. Swineinfluenza A (H1N1) strikes a potential for