TRAVELBy Dr Salim Parker SASTM PresidentSASTM

MEDICINE

At least 50 million deaths, including 10million in India alone; that’s what the1918 Spanish Flu’s frightening legacy is

frequently revealed as. A number of victimsindeed succumbed to the influenza virus. Therapid deterioration due to the devastatingvirus in previously healthy young adults wasdescribed as: ‘Two hours after admission theyhad the Mahogany spots over the cheekbones, and a few hours later you can begin tosee the cyanosis extending from their earsand spreading all over the face, until it is hardto distinguish the coloured men from thewhite.’ But this occurred in the minority ofcases. It was more a case of: If in the midst ofautumn, can winter be far behind?

Epidemiological studies showed that themajority of cases succumbed 7-10 days afterthe onset of symptoms, implying a differentcause as death due to the influenza virus isnormally rapid. A review of autopsy studiesafter the epidemic revealed that the vastnumber of deaths, in some cases up to 90%,could be a traced to a different organism. Arecent re-examination of lung specimens ofthat era again showed consistent evidence ofthis, either this organism alone orsuperimposed on the influenza virus. We nowknow that in these cases the primaryinfluenza viral infection was followed by amore lethal bacterial infection. And thecommonest bacterium identified, even inEurope and first world countries, is theorganism responsible for most cases ofcommunity acquired pneumonia (CAP),namely Streptococcus pneumoniae, alsoknown as pneumococcus.

It is known that an influenza viralinfection denudes the epithelial lining of therespiratory tract and exposes the basementmembrane. Up-regulation of molecules thatthe pneumococcus uses as receptors thenoccurs, facilitating adhesion of the bacteriaand subsequent invasion. The phagocytesthat are supposed to attack the invadingbacteria are impaired as well, and othermodes of suppression of an effectiveimmune response occur. All these factorsallow the pneumococci to more easilyinvade and cause infection, increasingmorbidity and mortality.

According to the World HealthOrganisation (WHO), about 1.6 million dieannually due to pneumococcal infectionsworldwide; one of the leading causes ofdeath on earth. In South Africa, tuberculosishas been the leading cause of death from2009 to 2013, followed by influenza andpneumonia classified together. The diseaseburden due to pneumococcus is the highestin the under five age group, with a secondpeak with a disproportionately higher

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mortality found in the elderly, especially in themore affluent countries. In the United States,about 500 000 cases of pneumonia occursannually due to pneumococcus, with 40%requiring hospitalisation. A number of factors,such as age over 65, diabetes, smoking,chronic cardiovascular and pulmonarydiseases and immunosuppression such as HIVinfection increases the risk of acquiring thispotentially fatal pathogen.

Prevention of respiratory infections is notcommonly discussed in the travel medicineconsultation, and in fact does not featureamongst the top ten topics such as diarrhoeaand malaria prevention. Yet respiratoryailments are the second commonest travelrelated presentations after diarrhoea duringtravel, and, in some studies, the commonestproblem post travel. Lower respiratory tractinfections (LTRI) are more common in theolder traveller and in one investigation nearlya quarter of febrile returning travellers hadLRTI. We have to remember that about 50%of those attending a travel clinic will be overthe age of fifty, a third over sixty, and 1.5%

The Unholy Alliance: Influenzaand Pneumonia

The pneumococcus bacteria

TRAVEL MEDICINE

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over 80. The older person will travel and needsprotection against, as described by Sir William Osler, the‘friend of the aged..... as it kills them gently withoutsevere symptoms.’ In fact he said that: ‘To die ofpneumonia is almost the natural end of old people.’

We of course beg to differ, as even in the winter ofour despair spring cannot be far behind. A very effectiveconjugate vaccine has led to a significant reduction ofpneumococcal disease in the paediatric population inSouth Africa. This vaccine is part of the routine childhoodvaccination schedule and in the United States has hadsome protective effect on the older population due to theherd effect. In a large study in the Netherlands recently inwhich 85000 people over the age of 65 were followed(Community Acquired Pneumonia Immunization Trial inAdults –CAPiTA study), there was a 45% reduction in theincidence of CAP in those vaccinated compared to theirnon-vaccinated counterparts.

Pneumococcus has more than 90 different serotypesand the current conjugate vaccine only protects against13 of about 30 types that cause disease. A polysaccharidevaccine which covers 23 serotypes is also available. Theadvantage of the conjugate vaccine is that it induces longterm immunological memory, reduces herd carriage, iseffective in infants, gives prolonged protection and can beboosted. A currently employed strategy as recommendedby the Advisory Committee on Immunization Practices(ACIP) is to first give the conjugate one in vaccine naiveadults over 65 years of age, followed 6-12 months laterby the polysaccharide vaccine, with a minimum interval ofat least eight weeks. Those who had the polysaccharidevaccine before should wait a year before taking theconjugate vaccine.

The double threat of influenza and resultantpneumonia should be discussed with all travellers,especially the elderly. The wily influenza H3N2 strainhas drifted slightly this year, resulting in a vaccineefficacy of only 18% in the northern hemisphere. H3N2

leads to more serious disease in theelderly, and subsequent pneumococcalinvasions with its associated morbidityand mortality is a real risk. MassGatherings such as the Hajj have beenidentified as having a high incidence ofboth influenza and pneumonia.Vaccinating against influenza annually isnow standard practice in the elderly.Vaccinating against pneumococcus,whether travelling or not, should bestrongly considered to keep at bay, againaccording to Sir Osler, ‘The Captain of theMen of Death.’

The influenza virus denudes the epitheliumand exposes the damaged basementmembrane to attacks by pneumococcus

The epithelial lining of the respiratory tractis exposed to many potential pathogens

Upregulation of receptors thatpneumococcus uses occurs

Pneumococci have an 'easy ride' invadingcells

Public campaigns acknowledge the link betweeninfluenza and pneumonia

The 1918 Spanish Flu led to the death of more than 50 million. Pneumococcus is thought to have the thecause in the majority of cases

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