SYMPOSIUM


time intra-airplane transmission was documented.29


Zika virus appears to


have arrived in the Americas, probably Brazil, from French Polynesia between May and December 2013, following the pathway of chikungunya and dengue viruses.30-32


West Nile virus was shown


to move across country borders by air travel of infected mosquitoes.33 We have seen an important growth


in food importation in the United States with a growing cost from $40 billion in 1998 to more than $70 billion in 2007.34


On average, each person


in the United States consumes 390 pounds of food (19 percent of the total) imported from another country.35 CDC estimated that one in six people in the United States (48 million cases per year) develop foodborne disease,36 with produce now being associated with nearly half of the cases.37


This


is compounded by the emphasis on eating fresh vegetables for health purposes.38


Because of good crop


growth, proximity, and the North American Free Trade Agreement, Mexico now provides almost half of the imported vegetables and vegetable products brought into the United States.34


THE CLIMATE AND THE ENVIRONMENT


The global warming being experi- enced presents challenges to humans and wildlife through a series of chang- ing interactions with insects and mi- crobes.39


With warmer temperatures


and increased rainfall, mosquito- transmitted


infections may be en-


hanced (e.g., Zika virus, dengue, and malaria). With the El Niño Southern Oscillation, we are seeing important weather changes; elevation in sea surface temperatures, especially as- sociated with water-related infections (cholera and non-cholera Vibrios); drought linked in some areas with the emergence of hantavirus pulmonary syndrome; and crop failure and fam- ine in areas, leading to migration along with undernutrition and decreased hydration,40


all of which contribute to a greater impact of infectious disease. 34 TEXAS MEDICINE February 2017 DEFORESTATION AND REFORESTATION


Deforestation in the Amazonian ba- sin and other areas of the world has changed local ecosystems and vector communities, exposing humans and livestock to new arthropod-borne eti- ologic agents such as Crimean-Congo hemorrhagic fever. Deforestation may bring together infected bird popula- tions into areas where humans live. Deforestation of tropical forests in- creases contact between hunters and wildlife. Clear-cut logging is likely to be less associated with human infec- tious disease transmission than se- lective extraction involving greater human activity and exposure during the construction of roads and trans- portation of workers. The emergence of Lyme disease in Europe and the United States appears to be related to reforestation resulting in increasing populations of deer and the vector of disease, the deer tick.41


PREDICTING THE NEXT IMPORTANT PANDEMIC


While endemic rates of important infectious diseases will continue in the United States, the past and future pathogens of greatest concern for outbreaks are new RNA viruses fall- ing within well-recognized families of Filoviridae, Bunyaviridae, Ortho- myxoviridae, and Flaviviridae. (See Table 1.) While viral infections in Western civilizations have been tracked since the 1930s, beginning in the early 1950s until the present time we have seen between three and four new vi- ral species emerge each year.42


RNA


viruses undergo mutational variations because of the high rate of error of the viral polymerase enzymes responsi- ble for genome replication compared with DNA viruses.19


and human viruses.44 This gene swap-


ping characteristically occurs in a permissive host such as a pig infected with avian and human influenza vi- ruses facilitating a new strain with a unique hemagglutinin surface pro- tein45


from previous exposure.20


to which humans lack immunity In 1997, a


new recombinant Rift Valley bunya- virus outbreak was seen in Kenya and Somalia after a period of abnormal rainfall.46


Genetic recombination also


explains the emergence of new coro- naviruses such as SARS.47


Reassort-


ment is an evolutionary mechanism for the viruses48 the price.


with humans paying The list of re-


cently emerging RNA viral infections includes Hantavirus pulmonary syn- drome, SARS, dengue, chikungunya fever, Ebola, H1N1 influenza, and Zika. Segmented RNA viruses undergo


gene reassortment important in pan- demic influenza strains43


where new strains are reassortments of animal


PROTECTING THE PUBLIC FROM INFECTIONS Because of the slow development of effective antiviral drugs, health au- thorities have focused on attempting to control epidemics by employing traditional public health measures. The backbone of public health con- trol is etiologic diagnosis and epide- miological surveillance. Because of the importance of animals as reser- voirs of new pathogens, public health leaders and clinicians need to com- municate with veterinary science leaders to help identify public health opportunities. Speed is important in defining the epidemiology of emerg- ing or reemerging infectious diseases so that control measures can be im- plicated before the disease reaches high rates of endemicity. Because the most communicable viruses contain RNA, they are subject to diagnosis with nucleic acid detection methods. Genomic approaches to discovery of new pathogens, including polymerase chain reaction, microarrays, and next- generation sequencing methods, are vital to keep ahead of viral pathogen discovery.49 Improved methods of global sur-


veillance are necessary, and syndrom- ic monitoring of diseases must be established in U.S. communities. We need early detection methods that de- liver real-time data through ongoing programs of active surveillance. Be-


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