Bioterrorism Agents: Plague Lesson 1 Introduction and Overview

Objectives Identify plague bacterium Epidemiology Natural Occurrence Introduction and Objectives Being prepared for bioterrorism means understanding the diseases on which they’re based. This course has been designed to teach you about the natural epidemiology of plague and how to manage it as both a natural disease and an intentional attack. In this lesson, we will give you a general overview of plague. At the end of this lesson you should be able to: Identify the bacterium that causes plague Describe the epidemiology of naturally-occurring plague Identify where cases of plague occur naturally

Bio-Terror Threat Plague can cause large numbers of cases Could create panic Considered for use since 14th century Bio-terror Threat Many biological agents could be used to intentionally harm civilians. However, only a few, such as Yersinia pestis, the bacterium that causes plague, have the ability to cause large numbers of cases of severe or fatal illness. This could create panic and requires special actions for medical and public health preparedness. Concern about the use of plague as a weapon isn’t just hypothetical. It has been considered for use in warfare since the 14th century to kill, disable and instill fear in the enemy.

Clinical Syndromes Bubonic Pneumonic Septicemic Plague Meningitis Pharyngeal Clinical Syndromes Plague is an acute and potentially fatal bacterial infection that affects humans and animals. It is caused by Yersinia pestis, a gram-negative, bipolar-staining, pleomorphic coccobacillus. Plague usually presents as one of five principal clinical syndromes: Bubonic Pneumonic Septicemic Plague meningitis Pharyngeal Descriptions of the characteristics of these different syndromes are provided on the following pages. “Safety Pin” Y. Pestis in blood

Bubonic Plague Infected flea bite Exposure through break in skin No person-to-person Untreated progresses to pneumonic Bubonic Plague Infection is transmitted by the bite of an infected flea or exposure to infected material through a break in the skin. Bubonic plague cannot be transmitted from person to person. If bubonic plague is not treated, the bacteria can spread through the bloodstream and infect the lungs, causing a secondary infection of pneumonic or septicemic plague.

Pneumonic Plague Inhalation of plague bacteria Disease progression Respiratory failure Shock Rapid death Person-to-person transmission Pneumonic Plague Pneumonic plague is a pulmonary infection that occurs upon inhalation of plague bacteria. Without early treatment in less than 24 hours, pneumonic plague almost universally leads to respiratory failure, shock, and rapid death. Pneumonic plague can be transmitted person to person through respiratory droplets with direct close contacts.

Septicemic Plague Primary Form Secondary Form Direct inoculation in bloodstream Secondary Form Development of untreated pneumonic or bubonic plague Septicemic Plague The primary form of septicemic plague results from direct inoculation and multiplication of plague bacilli in the bloodstream. The secondary form is a development of untreated pneumonic or bubonic plague. Other Forms of Plague Other forms, such as plague pharyngitis, ocular plague, and plague meningitis, are less common, though can be seen depending on the manner of exposure to the plague bacterium.

Epidemiology Natural Reservoirs Bites of infected flea Most common – Oropsylla montana Blood meal from bacteremic animal Regurgitates into human/ animal host Common reservoirs Deer mice Ground squirrels Epidemiology – Natural Reservoirs Humans acquire plague most often through the bites of infected rodent fleas. For naturally occurring cases of plague, the Oropsylla montana flea is the primary vector for plague. This type of flea is found mostly in rural rodent species, particularly the Rock Squirrel in New Mexico and Arizona. Urban plague from rats has not occurred in the U.S. in over 70 years. This is due to good public health surveillance and control and improved sanitation measures. If an urban plague event (natural or bioterrorism related) was to occur, the Xensopsylla cheopsis flea or "rat" flea would be the flea of most concern. The flea ingests a blood meal from a bacteremic animal. The bacteria multiply and block the gut of the flea. When the flea attempts to feed again, it regurgitates bacteria into human or animal mammalian host. The most common reservoirs for the bacteria are ground squirrels and wood rats.

Epidemiology Transmission Bite of infected flea Respiratory droplets Direct contact (6 feet) Direct skin/mucous membrane less common BT event – Respiratory droplets or aerosols Epidemiology – Transmission Transmission occurs through: the bite of an infected flea respiratory droplets, or direct contact with a patient infected with pneumonic plague. Transmission by direct skin or mucous membrane contact with tissues and fluids of infected animals is less common. Infection via inhalation of infective respiratory droplets or aerosols is rare with naturally occurring plague in the United States, but is the most likely route of transmission in a bioterrorist event. Becoming infected naturally through the respiratory route requires direct and close (within 6 feet) contact with an ill person or animal and has not occurred in the United States for decades.

Plague Incidence United States,1970-2003 Endemic to US Bubonic Most Common 83% Bubonic 2% Primary Pneumonic 15% Septicemic 5 to 15 cases per year Greatest Concentrations Arizona, Colorado, New Mexico, Utah Incidence in the United States Since 1900, plague has been endemic in the U.S. Between 1970 and 2003, 2% of plague has been pneumonic, 83% has been bubonic and 15% has been septicemic. Approximately 5 to 15 cases occur each year in the U.S. The greatest concentration occurs in Arizona, Colorado, and New Mexico. But human cases have occurred in rural areas from the Pacific coastal region eastward to the Great Plains states. Between 1970 and 2003, case numbers have ranged between 1 and 40 cases each year in the U.S. Peak occurrence is between April and November. The last time person-to-person transmission occurred in the U.S. was during the epidemic of 1924-1925 in Los Angeles, California.

Plague Case Fatality Rates United States, 1970 - 1977 In US, 14% died Untreated – 50 to 90% Treated – 15% Deaths mostly from delays in diagnosis and treatment Plague Case Fatality Rates in the United States, 1970 - 1977 In the United States, between 1970 and 1977, approximately 1 of 7 (or 14%) people infected with plague will died. Untreated Plague has between 50 and 90% mortality When treated, plague patients experienced 15% mortality Complications and death arise mostly from delays in diagnosis and treatment

Plague Incidence Worldwide, 1970 - 1998 All inhabited continents, but Australia 1,500 to 3,000 cases annually Greatest Concentrations Asia, South America Plague Worldwide Plague exists in rodent populations on every inhabited continent except Australia. Approximately 1500 to 3000 cases of human plague are reported annually worldwide. Worldwide, most cases of plague occur in Africa with limited outbreaks in Asia and South America.

Plague Bioterrorism Scenario Most dangerous as aerosol Outbreak of pneumonic Possibly pharyngeal or ocular Report all suspect cases to public health immediately Bioterrorism Scenario- Aerosolized Y. pestis If Yersinia pestis were to be used as a bioweapon, it would be most dangerous if released as an aerosol. An aerosol release would be expected to result in an outbreak of the pneumonic form of plague. Aerosolized Y. pestis would be most likely to cause the pneumonic form of plague, which is highly lethal and contagious. Aerosolized Y. pestis may also cause the less common pharyngeal and ocular plague. An immediate and coordinated public health and medical response would be required in the event of the intentional use of plague. Therefore, any case of plague should be reported to the state health department immediately. Reporting is especially important when a case of plague occurs outside of a typically affected area.

Review Questions – Plague Lesson 1 Overview

Plague Review Questions Lesson 1, Question 1 Santa Fe, New Mexico hospital Treating suspect plague case Hearing of more cases in area When do you start to worry about bioterrorism? You work in a hospital in Santa Fe, New Mexico. You’ve seen a few people with pneumonic plague in your years there. You’ve called the health department about the case you’re currently working up, but start hearing of a few more in your hospital and in other hospitals in the area. When would you start worrying about bioterrorism?

Plague Review Questions Lesson 1, Question 1 When do you start worrying about bioterrorism? Unrelated clusters Unusual rise in cases Both of the above None of the above When do you start worrying about bioterrorism in a place that would be expected to see normally occurring plague cases? When they start showing up in unrelated clusters? When you see an unusual rise in the number cases? Both of the above None of the above

Plague Review Questions Lesson 1, Question 1 When do you start worrying about bioterrorism? Answer - C. Both of the above Unrelated clusters Unusual rise in cases Answer C is probably the best answer to this question, since both unrelated clusters of illness and an unusual number of cases could be a cause of suspicion. Your public health agency should be contacted immediately.

Plague Review Questions Lesson 1, Question 2 Abnormally large, tender lymph node Right arm Lab specimen for preliminary testing What organism causes plague? You have a single patient in your Santa Fe, New Mexico hospital with an abnormally large, tender lymph node under the right arm. You send a specimen into the laboratory for preliminary testing. What organism would you expect to find they were “Unable to rule out?”

Plague Review Questions Lesson 1, Question 2 What organism causes plague? B. anthracis C. botulinum C. burnetii Y. pestis What organism would you expect to find on a patient presenting with symptoms of bubonic plague? B. anthracis C. botulinum C. burnetii Y. pestis

Plague Review Questions Lesson 1, Question 2 What organism causes plague? D. Y. pestis Yersinia pestis is the bacterium that causes plague. The bubonic form of plague can present with the abnormally large, tender lymph node.

Plague Review Questions Lesson 1, Question 3 New Hampshire hospital Labs – Unable to rule out plague Recent US travel Where in the US would you expect the patient to get plague? You work in a hospital in New Hampshire. A patient presents with signs and initial laboratory tests indicative of pneumonic plague. When you question the patient about recent travel, he tells you he has traveled in the United States. Where in the United States would you expect him to be exposed to the bacterium that causes plague?

Plague Review Questions Lesson 1, Question 3 Where in the US would you expect the patient to get plague? Western US, Southwest Eastern US, Southeast Northern US, Northeast Southern US, Southwest Where in the US would you expect your suspect plague patient to say he’d been traveling if it were naturally occurring plague? The Western United States, but mostly in the Southwest The Eastern United States, but mostly in the Southeast The Northern United States, but mostly in the Northeast The Southern United States, but mostly in the Southwest

Plague Review Questions Lesson 1, Question 3 Where in the US would you expect the patient to get plague? A. Western US, Southwest The best answer is A, the Southwestern United States. The United States experiences 5 to 15 cases each year in the Western United States. Most cases occur in the Southwest. International travel should also be considered. While most cases in the US do occur in the Southwest, we should also consider any of the Western states in any evaluation. We do not expect to see plague cases in the Southeast or Northeast. Patients should be asked if they have had any recent travel to the Western US or overseas.