key: cord-016312-u47mb2h0 authors: Lu, Pu-Xuan; Zhou, Bo-Ping; Gui-Lin, Yang; Qi, An title: Introduction of Emerging Infectious Diseases date: 2015-07-25 journal: Diagnostic Imaging of Emerging Infectious Diseases DOI: 10.1007/978-94-017-7363-8_1 sha: doc_id: 16312 cord_uid: u47mb2h0 Emerging infectious diseases (EIDs) refer to contagious diseases newly appeared, or with drug resistance, whose incidences have been rapidly increasing and are likely to further rise in the future. EIDs are usually discovered in three ways. Firstly, some existing diseases are ascertained as EIDs due to the recent discovery of pathogens. Secondly, previously considered noninfectious diseases are identified contagious as a result of new etiological findings. Thirdly, new infectious diseases are incurred by various complicated reasons such as evolution of pathogens. Due to their uncertainty and unpredictability, EIDs could result in high mortality and great impacts on social stability and economic development as people are unable to react immediately and take specific preventive or control measures. Therefore, EIDs have become a major public health problem worldwide. Cases in point are the epidemics of SARS in 2003 and H7N9 avian influenza around 2006, which have eloquently demonstrated their great threats to human health, society, and economy. In the coming twenty-first century, contagious diseases are expected to remain as a crucial public health concern for countries around the world. Pu-Xuan Lu , Bo-Ping Zhou , Yang Gui-Lin , and An Qi Emerging infectious diseases (EIDs) refer to contagious diseases newly appeared, or with drug resistance, whose incidences have been rapidly increasing and are likely to further rise in the future. EIDs are usually discovered in three ways. Firstly, some existing diseases are ascertained as EIDs due to the recent discovery of pathogens. Secondly, previously considered noninfectious diseases are identifi ed contagious as a result of new etiological fi ndings. Thirdly, new infectious diseases are incurred by various complicated reasons such as evolution of pathogens. Due to their uncertainty and unpredictability, EIDs could result in high mortality and great impacts on social stability and economic development as people are unable to react immediately and take specifi c preventive or control measures. Therefore, EIDs have become a major public health problem worldwide. Cases in point are the epidemics of SARS in 2003 and H7N9 avian infl uenza around 2006, which have eloquently demonstrated their great threats to human health, society, and economy. In the coming twentyfi rst century, contagious diseases are expected to remain as a crucial public health concern for countries around the world. At present, more than 40 kinds of EIDs have been found worldwide, and over 30 kinds have been reported successively in China. EIDs can be classifi ed into the following fi ve categories. Such contagious diseases did not exist in the past and newly emerge due to new pathogens such as AIDS, severe acute respiratory syndrome (SARS), human infection with highly pathogenic avian infl uenza H5N1, infl uenza A (HlN1), and human infection with avian infl uenza H7N9. Some existing diseases are not recognized as EIDs until recently, such as hepatitis D and E, legionnaire's disease, and Lyme disease. Some existing diseases considered noninfectious are found contagious in recent years, such as peptic ulcer caused by H. pylori and T-cell leukemia. Contagious diseases endemic in some places become prevalent in new places and then are generally considered as EIDs, such as West Nile virus (WNV) that was once popular in Middle East and Europe and broke out in the USA in 2012. Pandemic and subject to multiple infl uential factors. For example, diseases like Lyme disease, Legionnaires' disease, and peptic ulcer disease are globally distributed, SARS appears in 32 countries and regions, and BSE rages over 22 European countries. Highly contagious and complex in dissemination routes. EIDs like Ebola hemorrhagic fever, SARS, West Nile encephalitis, and mad cow disease are all highly contagious through various channels. Fast transmission with severe damages. AIDS, described as super cancer and the top killer in twentieth century, has been spreading across the world in an astonishing speed since diagnosed in 1981. In 2003, both the outbreak of SARS in spring and the highly pathogenic avian infl uenza H5N1 after mid-December caused casualties and huge economic losses. SARS, human avian infl uenza, and infl uenza HlN1 have all become rampant worldwide in a short time. Besides, convenient transportation and close international contacts also facilitate their spread. Zoonotic. More than three quarters of EIDs are zoonotic and closely related to animals. Researches by Jones et al. revealed that 60.3 % EIDs were zoonotic, with 71.8 % caused by wild animals, such as human avian infl uenza and Ebola virus. Diffi cult to prevent, diagnose, and treat due to the varied pathogens. Pathogens of EIDs mainly encompass viruses, bacteria, rickettsia, and chlamydia, predominantly viruses which are highly elusive and infectious. Free of natural immunity in human populations. With strong variability, the viruses of EIDs are able to escape the immune barrier and develop resistance to drugs in new hosts as the environment changes. Therefore, people have no immunity to EIDs. Biological factors. Pathogenic microorganisms may mutate to adapt new environment. Therefore, nonpathogenic strains may become pathogenic, and attenuated strains become virulent, or evolve into new pathogens, thus giving rise to EIDs. Pathogens may generate numerous mutant strains by acquisition, recombination, or transfer of genes in a short time, part of which may develop into new pathogens of contagious diseases. Natural factors. Global warming has changed the geographical distribution of vector insects and increased their reproduction speed and invasiveness. As a result, breeding time of pathogens outside human bodies is curtailed, making insect-borne contagious diseases more frequent. Social factors. Deforestation, construction of dams, and other human activities can change the ecological environment. Additionally, population movement, sexual promiscuity, drug abuse, and other bad behaviors may cause and spread contagious diseases. Clinical and Imaging Characteristics of EIDs Similar to other contagious diseases, EIDs progress through four periods: incubation period, prodromal period, period of apparent manifestation, and convalescent period. This period commences from the invasion of pathogens into human body and ends upon the appearance of clinical symptoms. This period spans from onsets to manifestation of evident symptoms. Clinical manifestations are usually nonspecifi c and shared by all EIDs, such as headache, fever, fatigue, and muscle soreness. It commonly lasts 1-3 days. After prodromal period, some patients with acute contagious diseases enter the period of apparent manifestation. During this period, all the signs and symptoms of the infectious diseases usually fully manifest. When human immunity grows to a certain extent, the pathophysiological changes would come to an end, and patients' symptoms and signs basically disappear, which is clinically called convalescent period. Some diseases can reoccur, and some may cause sequelae. Clinical imaging diagnosis is of great signifi cance for the diagnosis, differential diagnosis, and effi cacy evaluation of EIDs. In light of the strong infectiveness and variability of EIDs, imaging data are needed for their clinical diagnosis, differential diagnosis, treatment evaluation, and prognosis. Mostly caused by viruses, EIDs have mainly such pulmonary imaging changes as rapid occurrence of ground-glass opacity and (or) pulmonary consolidation. Cavity and cystic changes can also be seen in some cases. For some patients, imaging presentations and clinical symptoms and signs are not consistent. For example, the imaging fi ndings may be serious, while clinical symptoms are mild. For example, the pulmonary interstitial fi brosis lesions of patients with human avian infl uenza H5N1 may procrastinate for several years. During convalescent period, absorption of lesions is slow and imaging changes such as interlobular septal thickening and interstitial hyperplasia may be observed. For example, pulmonary fi brosis may be left in some SARS patients with severe pulmonary injuries after recovery as the absorption of pulmonary lesions take a long time. Moreover, patients with SARS or avian infl uenza H7N9 may be complicated with avascular necrosis of femoral head. Efforts shall be made to strengthen the surveillance of EIDs from organization system, personnel, equipment, and tech-nological competence. By monitoring and investigation, we could timely detect new sources of infection or new pathogens and infl uential factors and take prompt and effective measures to rein in their spread and contagion. A global coordinated information platform for EIDs prevention and control shall be established and improved where countries shall timely communicate epidemic situation of EIDs and share experience for EIDs prevention and control so as to block large-scale spreading. Public health infrastructure is fundamental to support public health preventive measures and to assess public health status. The high quality training of public health practitioners plays an vital role for the control of infectious diseases. Faced with the threats of emerging infectious, public health professionals should strengthen their training, and establish team culture to evaluate epidemiology of infectious diseases, thereby in the face of emerging infectious diseases outbreaks reasonable measures can be taken in an orderly manner to control the situation. 1. Conduct epidemiological studies to clarify the epidemic stages, characteristics, and infl uential factors of EIDs, so as to provide scientifi c evidences for formulation of prevention countermeasures 2. Accelerate the research and development of vaccines 3. Speed up the research of diagnostic reagents to form experimental methods for rapid diagnosis of EIDs 4. Carry out studies on pathogenic mechanism and early warning techniques for EIDs 5. Accelerate the research and development of new drugs, especially antiviral drugs 6. Build a strain resource bank of pathogenic microorganisms Overview of EIDS researches Isolation and characterization of viruses related to the SARS coronavirus from animals in southern China Research contents and methods of EIDS Chest X-ray manifestations of SARS Clinical characteristics and chest X-ray manifestations of severe SARS Study about indicators for beside radiogram and protection principles of infl uenza A (H1N1) Role of imaging in diagnosis of human avian infl uenza People's Medical Publishing House, Beijing Human avian infl uenza Epidemiological characteristics and pulmonary imaging fi ndings of human avian infl uenza Chest clinical imaging diagnosis of AIDS Viral hepatitis. People's Medical Publishing House EV-71Hand-foot-mouth disease. People's Medical Publishing House The epidemic situation and t prevention and treatment strategies for EIDS The epidemic characteristics and countermeasures of EIDS CD(4) (+) T lymphocyte count, and plasma HIV viral load: a study in 50 consecutive AIDS patients Relationship between respiratory viral load and lung lesion severity: a study in 24 cases of pandemic H1N1 2009 infl uenza A pneumonia Radiological features of lung changes caused by avian infl uenza subtype A H5N1 virus: report of two severe adult cases with regular follow-up Preservation of ecological balance and natural environment is the fundamental way to control and reduce zoonotic contagious diseases, therefore precluding EIDs from the source.