Landmark Developments in Infectious Diseases

A 20-Year Look-Back: Two Steps Forward, One Step Back

Ingrid G. Hein

Disclosures

October 20, 2015

In This Article

Emerging and Reemerging Infectious Diseases

The past two decades have made it clear how important public health measures and policies are in guarding against the spread of infectious diseases. In an increasingly global village, all people are susceptible to infection, no matter where they live. Moreover, resistance to antibiotics has made it difficult or impossible to treat more serious infections.

Dr Stephen Calderwood, president of the Infectious Diseases Society of America (IDSA), says that it is only in the past 20 years that we have learned about the effects of globalization, international travel, terrorism, human behavior, healthcare practices, animal-to-human transmission, and the importance of containment in the spread of infectious diseases.

He says we have come a long way in learning how to treat such diseases as HIV and hepatitis C virus infection. "The treatment of hepatitis C used to require 18 pills a day, and a weekly injection—a regimen with many side effects. Today, the virus is completely eradicated with just 12 weeks of antiviral treatment contained in a single pill." But, he says, we have a long way to go, and cooperation is needed on all fronts.

West Nile Virus

During August and September 1999, the United States experienced an outbreak of encephalitis in the New York City area, caused by the West Nile virus [1]—the first time the virus was detected in the Western hemisphere. Outbreak surveillance identified 50 hospitalized patients, seven of whom died.

The West Nile virus is thought to have entered the United States in an infected bird or mosquito and has continued to pose a threat. Today, this mosquito-borne disease is endemic across the United States. Outbreaks of the virus have also occurred in Canada (1999-2007), Israel (2000), and Greece (2010).

According to a 2001 study published in the New England Journal of Medicine,[1] the 1999 West Nile virus disease outbreak proves once again that, with the growing volume of international travel and commerce, exotic pathogens can move between continents with comparative ease.

Severe Acute Respiratory Syndrome

In November 2002, another virus crossed the ocean from China, causing a worldwide pandemic of severe acute respiratory syndrome (SARS). More than 8000 cases were reported. Canada was the second most infected country, with 251 cases and 44 deaths. For the first time, the World Health Organization (WHO) issued a travel advisory. SARS resulted in more than 774 deaths—a 9.6% fatality rate.

The SARS experience increased our understanding that rapid and transparent information-sharing between countries is critical to prevent the international spread of deadly infections.[2]

Cholera

Cholera, a disease thought to have been eradicated in Haiti for at least a century, broke out in October 2010, after the country's devastating earthquake in January of that year. One year later, more than 470,000 cases of cholera were reported, in Haiti, with 6631 deaths. The source of the outbreak was believed to be bacteria introduced into Haiti by a United Nations aid worker.[3]

Anthrax

"In the month after the Twin Towers attack, there was anthrax, and we had our seminal moment realizing that health played a big role in national security as well. Bioterrorism was a real threat," said Dr Alexander Garza, former chief medical officer for the US Department of Homeland Security from 2009 to 2013.

The mailing of anthrax spores through the US postal system in 2001, targeting politicians and news organizations, made it clear that infectious diseases could be spread with human intent. At least 22 people were infected, 11 of whom developed the life-threatening inhalational variety of anthrax infection. Five people died of inhalational anthrax.

Dr John G. Bartlett, professor emeritus, Johns Hopkins University School of Medicine, Baltimore, Maryland, and expert advisor for Medscape on infectious diseases and HIV, says that it was thanks to infectious disease specialist Dr Larry M. Bush that the anthrax was identified. Summoned to a Florida hospital emergency department, Bush found patient Robert Stevens unconscious from meningitis. When Bush examined the patient's cerebrospinal fluid, he saw that it was cloudy, and under the microscope he saw many polymorphonuclear white cells and many large gram-positive bacilli, both singly and in chains. Bush identified it as anthrax—a terrifying and fatal pathogen.[4]

The clinical laboratory of the medical center presumptively determined the organism to be Bacillus anthracis, and this was confirmed by the Florida Department of Health laboratory on the following day.[4]

Fear ensued. The threat of anthrax caught the country by surprise, making it clear that health and security were linked. Garza says that since the anthrax scare, the government has a much better forensic capacity. "The world of microbial forensics did not exist back then," says Garza. "Now we can decode DNA in a day. We've come a long way in knowing how to better deal with those situations," says Garza.

Middle East Respiratory Syndrome

Most human cases of Middle East respiratory syndrome (MERS) have been attributed to human-to-human transmission, which occurred most often in hospital settings. However, it is believed that the first infection came from direct or indirect contact with infected dromedaries.[5] MERS was first reported in Saudi Arabia in 2012 and has since spread to several other countries, including the United States.

Most people infected with MERS-coronavirus (MERS-CoV) developed severe acute respiratory illness, including fever, cough, and shortness of breath. As of February 2015, the WHO had received reports of 971 laboratory-confirmed cases of human infection with the MERS-CoV, with at least 356 deaths.[6]

Avian and Swine Flu

Avian influenza has been a public health concern throughout the past 20 years, raising awareness of the possibility of animal-to-human transmission of disease. In June 2009, the novel H1N1 virus (known as swine flu) originated in Mexico and caught the attention of the public media.

Novel H1N1 showed the world how the influenza virus form new virus combinations to which humans do not have immunity. It also defied all standard teaching, appearing to come from the Western hemisphere in the summertime, whereas all previous epidemics originated from Asia in winter.

Dr Anne Schuchat, head of science and public health at the Centers for Disease Control and Prevention (CDC), called the virus "an unusually mongrelized mix of genetic sequences from North American pigs, Eurasian pigs, birds and humans."[7] The final estimates indicated that approximately 60.8 million cases occurred worldwide from April 12, 2009, to April 10, 2010. In the United States, the H1N1 virus was responsible for 274,304 hospitalizations and 12,469 deaths.[8]

Ebola

Ebola has become the most challenging global public health emergency of the past 20 years. In the largest outbreak of the disease to date, 10 countries have been affected; more than 27,000 people have been diagnosed with suspected, probable, or confirmed Ebola infection; and more than 11,000 have died.

Ebolavirus was first identified in humans in a 1976 outbreak near the Ebola River in the Democratic Republic of the Congo (formerly Zaire).[9] John Bartlett says that the outbreak was managed by drawing a circle around Yambuku and disallowing entry or exit (a quarantine).

The recent outbreak in West Africa has been much more difficult to control. "It's like fighting a forest fire," said CDC director Dr Tom Frieden during the epidemic. "Leave behind one burning ember, and the epidemic could reignite. That ember could be one case undetected, one contact not traced, one healthcare worker not effectively protected, or one burial ceremony conducted unsafely."[10]

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