The study of infectious diseases has always been crucial to mankind because of the devastating effects it has had on the human race. The influenza epidemic, for example, occurred repeatedly in the 20 th and 21st century, spreading across large regions and multiple continents. Influenza in 1918 killed an estimated 50 million people world wide. This was higher than the amount of people that died in World War I. About 500,000 fatalities occurred in the US which was approximately 28% of the US population at that time. The number of deaths that took place in 1957 and 1968 were lower than in 1918. According to Luk, 70,000 deaths of Americans between 1957 - 1958 resulting from the spread of flu from China (Luk 1378). All of these factors pose new health challenges for medical experts, public health officials and health care administrators. health threats and challenges for public health official. The purpose of this essay is to understand the background history and to gain a perspective on the current etiologies of infectious disease in the United States today.
A discussion on the history of epidemics was presented by Nelson and Williams (Nelson and Williams 205). They state how epidemics of infectious diseases have been recorded as early as 430 BCE (before the Christian era) in Athens. The influx of Greeks to Athens stirred up a plague of infectious disease which killed a large percentage of the population of ancient Athens. The cause of this epidemic in Athens still remains inconclusive. The plague contributed to the collapse of empires such as the Han dynasty of 160 CE (common era) and the Roman empire of 165 - 180 CE (Nelson and Williams 206-7). Fatalities due to infectious diseases had a profound effect on politics, culture, religion and societies. The Bubonic plague, small pox and measles were the most devastating epidemics in history. Ninety percent of Europeans were killed by the plague, four centuries later (1104 - 1110 CE). By 1345 CE the Bubonic plague, or Black Death as it was then called, swept across Europe again (Nelson and Williams 208). The first recorded cases of the plague were said to have been seen in China in the 1330’s. The most significant outbreaks of Black Death transpired in Europe starting from the lower Volga, Russia and spreading to Italy and Egypt. Merchant ships carrying rats and fleas spread the infectious disease from China to Europe (Nelson and Williams 209). From 1347 - 1351, three out of ten Europeans were killed, leaving approximately 24 million Europeans dead with a total of 40 million deaths worldwide (Nelson and Williams 210).
Small pox is one of the greatest epidemics in human history. It was first recorded in 1350 BCE during the Egyptian - Hittie war, appearing in agricultural settlements in northeastern Africa around 10,000 years ago. Egyptian merchants were known to spread it from Africa to India (Nelson and Williams 2013).. Well-known skin bumps were found on mummies from that era from which the name small pox emerged. Small pox also spread to the Spanish and Portugese population where a mortality rate of 60 - 90% was described by Spanish priest Fray Toribio Motolinia. Around one thousand people died per day in Tlaxcala, Mexico. The American population was not spared of the spread of small pox. In 1721, in Boston about 5,980 of the city’s 11,000 residents were afflicted with small pox with about 844 deaths (Nelson and Williams 215). Survivors of small pox were known to be immune to re-infection after further exposure. The practice of intentionally exposing people to the infectious diseases was called inoculation or variolation. It was used in China, Africa and India before it was later adopted in Europe and the Americas. Several other accounts that describe epidemics of infectious disease recorded in ancient history are leprosy, tuberculosis, dysentery, meningococcal infections, fevers in the 17th century settlements, diphtheria in the early 18th century, yellow fever and cholera of the late 18th and 19th centuries, poliomyelitis, measles and whooping cough. There has been an emergence of new infectious disease such as HIV/AIDS , Ebola virus diseases (EVD), Legionnaires’ disease, Lyme disease, toxic shock syndrome and several others (Nelson and Williams 217).
According to the WHO. the first case of Ebola emerged in Nzara town, Sudan and Yambuku, in Democratic of Congo (Zaire) in 1976, where simultaneous outbreaks occured. Ebola was named from the Ebola river in Zaire. A mortality rate of 53% was recorded in Sudan while 8 8 % was recorded in Zaire (World Health Organization). Since first being discovered in 1976, this most recent outbreak of Ebola is considered the biggest and most seriously complex. (World Health Organization). The countries with major outbreaks were in West Africa (Liberia, Sierra Leone and Guinea). It later spread to other parts of West Africa such as Nigeria, Senegal, Mali and other parts of the world including Spain, Scotland and the United States of America. According to the National Institute of Health, infectious disease if not controlled, leads to an epidemic and under extreme circumstances it leads to a pandemic as seen with the case of Influenza (National Institute of Health 4)
An infectious disease is defined as “the invasion of a host by agents such as bacteria, viruses, fungi, or parasites and can be transmitted from one person to another, either directly or indirectly.”(National Institutes of Health 3). Infectious disease is a problem affecting persons and countries around the globe, including the United States. Between the years 1998 – 2006 for instance, in the United States alone there were over 40 million persons hospitalized due to infectious disease (CDC). In addition, between 1980 and 1999, mortality from infectious disease in the United States experienced nearly a 5% increase, a sizable increase which is considered reflective of the widespread prevalence of human immunodeficiency virus at this time. Infectious disease have peculiar behavior which add to their pervasive threat level. Infectious diseases appear in new forms as emerging diseases, they disappear or are thought to be eradicated but then suddenly reappear. Certain chronic diseases are sometimes reclassified as having etiologies that are infectious, as well.
Emerging infections include known diseases that have entered into new areas as well as the re-identification of diseases that were previously not detected. Emerging infections include both the identification of previously undetected. In the United States, the HIV/Acquired Immune Deficiency Syndrome (AIDS) was classified as an emerging disease in 1979. By 2010, an estimated 1 million people were living with HIV infection. Over 650,000 fatalities had completed over the time span of this epidemic. On the other hand, West Nile virus, a pathogen discovered in 1937 in Uganda, was introduced into the US in 1999, where it subsequently established itself across the continental US (Fauci 677).
Reemerging diseases are defined as the return of a recognized disease after a decline in incidence. For the US, this includes both vaccine-preventable diseases and drug-resistant pathogens. Vaccination protects individuals against many childhood illnesses; however, a small minority of US parents now actively refuse to vaccinate their children, which potentially leads to increased transmission of these diseases. Drug-resistant microbial pathogens, such as Clostridium difficile, have also come to the forefront of public health attention in recent years and may be classified as a reemerging infectious disease (Faust 680).
The magnitude of concern regarding antimicrobial resistance was evident in German Chancellor Angela Merkel’s request for infectious diseases and antimicrobial resistance as major topics for discussion at the June 2015 G7 Summit12 and US President Barak Obama’s request to the US Congress for $1.2 billion for a five-year action plan against antibiotic-resistant "superbugs" (Fausti 676). These previously overlooked infections remain a significant cause of mortality. Finally, recent scientific breakthroughs have forced researchers to rethink disease categorization with the discovery of infectious causes of chronic diseases. The linkage of cervical carcinoma, a chronic disease, with human papilloma virus (HPV), an infectious agent via person-to-person direct contact, added further complexity to the study of infectious diseases. Many other cancers are associated with human papilloma virus (HPV), but, at this time, cervical cancer is the only cancer for which HPV is considered a necessary cause for cancer development.
Since 1900, with the exception of the Spanish flu pandemic, which killed millions of Americans, non-infectious causes have contributed more deaths annually in the US than infectious causes. From 1900 until 1936, infectious disease mortality in the United States declined at a rate of 2.7% annual percent change (APC) (CDC). In 1935, the antibiotic era was shepherded in with the discovery and use of sulfa drugs which accelerated the decline of infectious disease deaths to an APC of 8.5%, from 1936 to 1955. From 1955 to 2013, the infectious disease mortality slowed to a decline of 0.4%. Since the 1950s, non-infectious causes have accounted for 95% of US mortality with infectious diseases accounting for the remaining 5% (CDC). In 2013, the last year for which data were available, 43 deaths per 100,000 were attributed to infectious causes (CDC).
In the following portion of my discussion I shall include information obtained from the Centers for Disease Control and Prevention online database which contains current and historical data tables for all areas of the United States as well as epidemiological data, including infection rates and mortalities.
In the late 1970's overall infectious disease mortality were rising and strong. Infectious disease mortalities nearly doubled from from 31.6 per 100,000 in 1979 to 63.5 per 100,000. The source of this doubling was indeed the HIV/AIDS epidemic just catching strength in the country and with virtually no treatment options developed at this point. Yet, the impact of medication is immediately clear even in the data. When anti-retroviral therapy medications were developed and released in 1995, suddently, HIV and AIDS related deaths took a sharp decline by 40% annual percent change, according to CDC estimates. After the initial drop, overall mortality due to HIV/AIDS continued to decrease with an annual percent change of 6.0% from 1997 through 2013. By 2013, AIDS related deaths have actually dropped so significantly that they are now in the range of -10.0% for annual percent change The overall annual percent change from 1995 In the last five years, there has been a significant decrease in APC of HIV/AIDS mortality by 8.0%. Before 1999, an average of 36 deaths per year in the US were attributed to vector-borne causes,, the majority of which were a result of spotted fevers. However, since 2002, West Nile virus had been reported in all but five states of the continental US, and vector-borne diseases have averaged 141 deaths per year for the US. Another area of concern for infectious disease is vaccine-preventable deaths have been decreasing since 1980, with an annual percent change of 2.4%, according to the CDC. Even despite these improvements, data indicate that in 2013, over 3,000 deaths due to vaccine preventable diseases occurred. The two major culprits for these deaths were sourced in Streptococcal pneumoniae, which had the argest influence on the trend, accounting for 72% (2,174 deaths) of vaccine-preventable disease mortality in 2013.
Influenza and pneumonia accounted for 41.5% of all infectious disease deaths in the US from 1980 to 2013. One area of concern, however, is resistant bacteria. Since the introduction of antibiotics to the general public in the 1940's, bacteria and other pathogens have evolved resistance to a number of once-effective drugs, and we are now seeing increasing mortality rates caused by pathogens once thought to be defeated. In 2008, the Antibiotic Resistance Genes Database collected resistance information on over 200 species and over 100 genera (Fauci 680). Hospital-acquired infections kill more than 63,000 patients in the US every year, 70% of these drug-resistant strains. are used for food animals than for humans. While the data used here are not specific to resistant strains, and include all pathogens known to have resistant strains, the CDC list indicates an increase in drug resistance while the WHO list illustrates a stable trend, mostly due to the inclusion of tuberculosis and hospital-acquired infections. Perhaps the most profound shift in the conceptualization of infectious diseases over the last three decades has been the recognition of infectious causes of chronic diseases. An estimated 99.7% of cervical cancer can be attributed to HPV infection.
Currently, over 4,000 Americans die each year from this disease. Researchers report a continued decline in mortality due to cervical cancer. While its contribution to overall mortality in the US is small it is remarkable that the discovery of HPV as a necessary cause for cervical cancer changes our perception of infectious diseases. Health care officials are now recommending that not only young women should be vaccinated, but also young men, in order to circumvent the serious rates of cancer mortality. Clinicians expect the rates of cervical cancer mortality to continue to decrease in the coming decades as this cohort ages. HPV is also linked to anal cancer, oropharyngeal cancers, vaginal cancers, vulvar cancers and penile cancers (Fauci 684).
As infectious causes of chronic diseases are recognized, new tools to prevent mortality may be possible. The 1950's saw a very successful introduction of the Pap smear, a screening tool against cervical cancer, which has been shown to lower cervical cancer mortality by over 50%. Although, mortality has been consistently declining since vaccines for specific infectious diseases became more common, there is still room for improvement. For example, the HPV vaccine has recently been developed only in the past 10 years. Clinicians and researchers have high expectations that this vaccine, if properly implemented, will be able to decrease mortality rates even further than has already been accomplished. As science improves our understanding of disease etiology, major epidemiologic shifts in diseases classified as either infectious or chronic are likely to be observed.
Works Cited
Fauci, Anthony S. "Infectious diseases: considerations for the 21st century."Clinical Infectious Diseases 32.5 (2014): 675-685
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Lapore, J. “It’s Spreading: Outbreaks, media scares, and the parrot panic of 1930.” American Chronicles.1st June 2009. Print
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the 1918 influenza pandemic." Clinical Infectious Diseases33.8 (2001): 1375-1378.
National Institutes of Health (US). Understanding Emerging and Re-emerging Infectious Diseases. Biological Sciences Curriculum Study. NIH Curriculum Supplement Series [Internet]. Bethesda (MD): 2007.
Nelson, Kenrad E., et al. "Infectious disease epidemiology theory & practice." (2001): 205.
Tuchman, Barbara W. "This is the end of the world”: The Black Death." A Distant Mirror —The Calamitous 14th Century (1978): 921-925.
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