From the Department of Emergency Medicine (Liu CL, Wang TL, Chen KC, Cong CF) , Shin-Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan
Correspondence to Dr. Tzong-Luen Wang, Department of Cardiovascular Surgery, 95 Wen Chang Road, Shin-Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan . E-mail m002183@ms.skh.org.tw
 

There have been a lot of changes in our life in last three decades. The first is improved agriculture that led to better nutrition. The second is improved hygiene and sanitation which reduced the transmission of many infectious diseases. The most important one is that new generation of antibiotics and passive immunities make people resistant to known diseases.¹
Declining infection rates and the changing age distribution of the population ever result in decreased importance of infectious diseases compared with other causes of death and disability. However, reemerging or drug-resistant infections have increased in the past two decades, and the incidences of these diseases threaten to increase in the near future. The infectious diseases include not only what had been recognized, but also the well-recognized pathogens which re-emerged as a threat to public health.
Drug-resistance was once perceived as primarily a problem in hospital-acquired infections. But now community-acquired infection has become increasingly drug resistant. It may be the results of interaction among the changes in society, technology and the microorganisms themselves. The pathophysiology of such newly developed infectious diseases and re-emerging contagious diseases deserves comprehensive understanding.

Accompanied with social change, the increasing frequency of both parents working outside the home has led to greater use of day care. It is affecting the emergence of infectious diseases. The combination of susceptible children in day-care facilities, inadequate hygiene, frequent infections, and unnecessary antibiotics for upper airway infection by local clinic are the main causes of drug resistance in such community-acquired infections. Urbanization is the trend of the world, but also intrinsically increases interpersonal contacts. The spread of infectious disease is directly proportional to the density of population, and a crowed metropolitan region is susceptible to spread disease than a rural area does. Poor hygiene, poverty and low socioeconomic status are all important contributing factors for contagious diseases.^1,2
Patients with certain immunocompromised conditions such as diabetes mellitus, chronic renal disease, chronic pulmonary disease and malignancy are at high risk of various infectious diseases. When chemotherapy for malignancy or immunosuppressive medication for organ transplantation are proved to make patient live longer, it also contribute to the emergence of infectious diseases. Aging, associated with physiological decay and development of systemic diseases, is another important factor associated with an increased susceptibility to infectious diseases.^1,2
A variety of human behaviors are also influencing the emergence of infectious diseases. The unsafe sex increases the frequency of gonorrhoea, syphilis, and HIV. The use of alcohol or illegal medicine increases the possibility of disease transmission. In addition, frequent contact with pets would be the more likelihood for zoonotic pathogen transmission.^1,2

As new technology developed, people enjoy the convenience and comfort, but the artificial environment may be also suitable for development of some specific disease. The linkage between air-conditioning cooling towers and Legionnaire? disease, super-absorbent tampons and toxic shock syndrome, the fast-food hamburger and E. coli O157:H7 examples. As new agricultural industry improved, antimicrobial agents used for promoting growth, preventing and treating disease in animals, these antimicrobial agent may in turn result in emerging pathogens and influence human later.

Many rumors may be spread by newspaper or radio just after disaster, for example, typhoid or rabies. It reflex the fear of people rather than the true imminent problem. Disaster may disrupt the original hygiene, piped water, and increase vectors for pathogen spread. However, natural disasters rarely results in outbreaks of infectious diseases. The most route is fecal contaminated water and respiratory droplets.¹³
Unburied body has minimal rate for pathogen transmission, especially cause by trauma. The risk may be higher among those handle dead bodies than the survivors in disaster. But the risk can be lowered by proper vaccination, protect devices and delicate behavior. In general, the risk of emerging disease seems not to increase in the settings of natural disasters. It depends upon the vaccination, sanitation and hygene.¹³

We have entered an era when microorganisms become more and more resistant to modern antimicrobial agents. Antibiotics abuse, urbanlization, people? behavior, and microorganism adaptation are all the critical contributing factors. It is essential to use antimicrobials wisely and judiciously. Good response planning and training may be the only way to manage a biological event, either natural or man-made.