The microbial threat in fragile times: balancing known and unknown risks.

Abstract

The infrastructures that protect public healthon a daily basis go mostly unnoticed untildiseases become a threat. News of E. coli inthewatersupply,BSEagentinthefoodchainor anthrax in the postal system puts thespotlight on the public health system andraises important questions about its abilityto keep the public safe.Microbes proliferate rapidly, mutatefrequently, and adapt easily to new environ-mentsandhosts.Numerousfactors,includinghuman activities, can accelerate and amplifythese natural phenomena (1). As a result,pathogens that are new to humans are beingidentifiedwithdisturbingfrequency.Epidemic-prone diseases such as dengue, yellowfever and meningococcal meningitis havebecome resurgent, sometimes in more viru-lentforms.ControlofTBandmalariathroughstandard measures is eroded by antimicrobialresistance. Diseases such as West Nile feverand Rift Valley fever have spread to newcontinents and become endemic there. Influ-enza — one of the most mutable viruses —demands regular worldwide surveillance topredictwhichstrainsarerequiredforvaccine,and to detect the next antigenic shift thatcould launch a global pandemic.In recent years, unusual epidemics aswell as new diseases have occurred on everycontinent. Some of the more spectacularrecent outbreaks in industrialized countrieshave been dueto changes in the behaviour ofa pathogen that allowed it to circumvent thedefences of public health. Examples includeE. coli serotype O157:H7 thriving in highlyacidic foods and beverages such as mayon-naise and cider, and BSE agent survivingall conventional deactivation procedures.It is in the developing countries, how-ever, that new diseases and outbreaks occurmost often. It is there too that the laboratoryandsurveillancecapacitytodetectandcontainthese diseases is sometimes lacking. In manyparts of the developing world people facebiological terror on a permanent basis in theform of diseases such as cholera, dengue,measles, meningitis, shigellosis, and yellowfever. Though Ebola gets spectacularpublicity whenever it occurs, it is thesemore common diseases, as well as AIDS,that can and do cause most devastationin the form of death, disability and economicloss.Beginning with the 1992 publicationof the US Institute of Medicine’s landmarkreportonemerginginfections,theresurgenceof infectious diseases has been viewed asa factor that can undermine national andinternational security (2). AIDS in particularconvinced the world that a previouslyunknown pathogen could destabilize wholeregions. The highly publicized emergenceof new diseases and re-emergence of others,combined with the increased speed andvolume of international travel, have madecountries aware of their vulnerability.With the use of anthrax to incite terror,a range of new issues arises within an alreadycomplex mix of competing priorities anduncertainties. Inunitingagainst theinfectiousdisease threat, how much priority should theinternational community give to an unknownyet potentially catastrophic risk, such as thedeliberate release of smallpox, when over14 million people continue to die each yearfrom well-known and often preventableinfectious diseases? What priority should begiventothestockpilingofvaccinesanddrugsagainst a possible bioterrorist attack whenso many millions of preventable deaths areattributed tolack of access toessential drugs?Since 11 September 2001, WHO hasoften been asked about how to respond toa bioterrorist attack. The answer is that theepidemiological and laboratory techniquesneeded to detect and contain an outbreak arethesamewhetherthatoutbreakisdeliberatelycaused or natural. Adequate data on theprevalence of natural background diseasesmake it much easier to recognize an unusualand possibly deliberately caused disease.The ‘‘invisible’’ infrastructure for globaldisease surveillance and response exists andis firmly in place. It is the Global OutbreakAlert and Response Network (GOARN),formally inaugurated by WHO in April 2001.A ‘‘network of networks’’, GOARN inter-links, in real time, over 100 existing networkswhich together possess much of the data,expertise and skills needed to keep theinternational community constantly alert tooutbreaks—whateverthecause—andreadyto respond. The network, which operateswithin the framework of the InternationalHealth Regulations, is supported by a com-puterized system for gathering disease intelli-gence, and makes full use of the power ofelectronic communications (3).Between July 1998 and August 2001,WHO verified 578 outbreaks of potentialinternationalimportancein132countries,andinvestigated many hundreds more. Twenty-two countries, many affected by complexemergencies, had 10 or more verified epi-demics.Themostcommonnaturaloutbreakswere of cholera, meningitis, haemorrhagicfevers, viral encephalitis, and anthrax (3).Theworldfacestheprospectofsurprisesarising from the volatile microbial world ona daily basis. The threats posed by infectiousdiseases have global causes and effects thatcanonlybemanagedwithglobalpartnershipssupported by strong national public healthcapacity.Foreignpolicy agendas whichaim atbuilding a more secure world are thereforeincreasingly including infectious diseaseprevention and control. As stated in Novem-ber2001intheOttawaPlanforImprovingHealthSecurity, strengthened global capacity forroutine disease surveillance and response isan essential component of preparedness for apossible attack using biological weapons (4).This approach is seen as a wise ‘‘dual use’’investment which prepares for a potentialsecurity threat while at the same time yieldinga clear benefit for public health.Such advice rings especially true for anever more interconnected world. Whetheroutbreaks are caused naturally or deliberately,and whether they start in developing orindustrialized countries, every country isvulnerable to them. When the worldstrengthens its defences against knowndisease threats it can only be better protectedagainst those that are unknown as well.