here Is Plague Found?

W

Plague is an infectious disease of animals and humans

caused by a bacterium named Yersinia pestis. People

usually get plague from being bitten by a rodent flea that

is carrying the plague bacterium or by handling an infected

animal. Millions of people in Europe died from plague in

the Middle Ages, when human homes and places of work

were inhabited by flea-infested rats. Today, modern antibiotics are effective against plague, but if an infected person

is not treated promptly, the disease is likely to cause severe

illness or death.

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Wild rodents in certain rural areas around the world are

infected with plague. Outbreaks of human plague still occur

in rural communities or in cities. They are usually associated

with infected rats and rat fleas that live in the home. In the

United States, the last urban plague epidemic occurred in

Los Angeles in 1924–1925. Since then, human plague in

the United States has occurred as mostly scattered cases in

rural areas (an average of 10 to 15 persons each year).

Globally, the World Health Organization reports 1,000 to

3,000 cases of plague every year.

In North America, plague is found in certain animals

and in their fleas from the Pacific Coast to the Great Plains,

and from southwestern Canada to Mexico. Most human

cases in the United States occur in two regions: 1) northern

New Mexico, northern Arizona, and southern Colorado;

and 2) California, southern Oregon, and far western

Nevada. Plague also exists in Africa, Asia, and South

America (see map).

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Plague is usually

transmitted to humans

by the bites of

infected rodent fleas.

During rodent plague

outbreaks, many

animals die and their

hungry fleas seek

other sources of

blood to survive.

Persons and

animals that visit or

live in places where

rodents have recently

died from plague risk

getting the disease

from flea bites. Persons also can become directly infected

through handling infected rodents, rabbits, or wild carnivores that prey on these animals, when plague bacteria

enter through breaks in the person’s skin. House cats also

1 Case

2–5 Cases

6–10 Cases

11–15 Cases

16–20 Cases

21 or more

Reported Human Plague Cases

by County: U.S., 1970–1997

CDC

CENTERS FOR DISEASE CONTROL

AND PREVENTION

/NCID NATIONAL CENTER FOR INFECTIOUS

DISEASES

Prairie dogs can harbor fleas

infected with plague bacteria.

DEPARTMENT OF HEALTH & HUMAN SERVICES

A QUICK

GUIDE

TO

PLAGUE

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Write: Division of Vector-Borne Infectious Diseases

National Center for Infectious Diseases

Centers for Disease Control and Prevention

P.O. Box 2087

Fort Collins, CO 80522

Call: (970) 221-6400

Fax: (970) 221-6476

Internet: http://www.cdc.gov/ncidod/dvbid/dvbid.htm

E-mail: dvbid@cdc.gov

For general information about plague

For local information about plague

World Distribution of Plague, 1998

Regions where plague occurs in animals

hat Is Plague?

ow Is Plague Transmitted?

Plague in the United States, 1970–1998

Arizona 55

Other 39 Colorado 38

California 36

New Mexico 191
are susceptible to plague. Infected cats become sick and

may directly transmit plague to persons who handle or care

for them. Also, dogs and cats may bring plague-infected

fleas into the home. Inhaling droplets expelled by the

coughing of a plague-infected person or animal (especially

house cats) can result in plague of the lungs (plague

pneumonia). Transmission of plague pneumonia from

person to person is uncommon but sometimes results in

dangerous epidemics that can quickly spread.

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The typical sign of the most common form of human plague

is a swollen and very tender lymph gland, accompanied by

pain. The swollen gland is

called a “bubo” (that’s

where the term “bubonic

plague” comes from).

Bubonic plague should be

suspected when a person

develops a swollen gland,

fever, chills, headache, and

extreme exhaustion, and has

a history of possible exposure to infected rodents,

rabbits, cats, or fleas. A

person usually becomes ill with bubonic plague 2 to 6 days

after being infected.

When bubonic plague is left untreated, plague bacteria

can invade the bloodstream. As the plague bacteria multiply

in the bloodstream, they spread rapidly throughout the

body and cause a severe and often fatal condition. Infection

of the lungs with the plague bacterium causes the pneumonic form of plague, a severe respiratory illness. The

infected person may experience high fever, chills, cough,

and breathing difficulty and may expel bloody sputum. If

plague patients are not given specific antibiotic therapy, the

disease can progress rapidly to death. About 14% (1 in 7)

of all plague cases in the United States are fatal.

ow Is Plague Diagnosed?

ow Is Plague Treated?

ow Can Plague Be Prevented?

food supplies, such as pet and wild animal food.

Make your home and outbuildings rodent-proof.

3 If you anticipate being exposed to rodent fleas, apply

insect repellents to clothing and skin, according to label

instructions, to prevent flea bites. Wear gloves when

handling potentially infected animals.

4 If you live in areas where

rodent plague occurs, treat

pet dogs and cats for flea

control regularly and do not

allow these animals to roam

freely.

5 Health authorities may use

appropriate chemicals to kill

fleas at selected sites

during animal plague

outbreaks.

PROPHYLACTIC

ANTIBIOTICS

Medical experts advise that antibiotics be given for a brief

period to people who have been exposed to the bites of

rodent fleas during a plague outbreak or have handled an

animal infected with the plague bacterium. Such experts

also recommend that antibiotics be given if a person has

been exposed to another person or to an animal (for

example, a house cat) with suspected plague pneumonia.

 Persons who must be present in an area where a

plague outbreak is occurring can protect themselves for

2 to 3 weeks by taking antibiotics. The preferred

antibiotics for preventing plague are the tetracyclines

or the sulfonamides.

VACCINES

Plague vaccine has very limited use. The following

persons should consider vaccination: 1) scientists who

work with the plague bacterium in the laboratory;

and 2) people in plague-infested areas who handle or

have close contact with potentially infected animals as

part of their routine work (such as rodent biologists).

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A combined approach using the

following methods is

recommended:

1) managing the

environment;

2) educating the

public on ways to

prevent plague

exposures;

3) preventive

antibiotic therapy;

and, rarely,

4) vaccines.

ENVIRONMENTAL MANAGEMENT

Effective environmental management of plague reduces the

risk of persons being bitten by infectious fleas of rodents and

other animals. Preventing plague outbreaks requires sanitation measures to reduce rat and other rodent populations in

places where people live, work, and play. It is important to

reduce food sources used by rodents and to make homes,

buildings, warehouses, or feed sheds rodent-proof. Applying

chemicals that kill fleas and rodents is effective but should only

be done by trained professionals. Rats that inhabit ships and

docks should also be controlled by trained professionals who

can inspect and, if necessary, fumigate cargoes.

PUBLIC HEALTH EDUCATION

In the western United States, where plague is widespread in

wild rodents, people living, working, or playing where the

infection is active face the greatest threat. Educating the general

public and the medical community about how to avoid exposure

to disease-bearing animals and their fleas is very important and

should include the following preventive recommendations:

1 Watch for plague activity in rodent populations where

plague is known to occur. Report any observations of

sick or dead animals to the local health department or

law enforcement officials.

2 Eliminate sources of food and nesting places for rodents

around homes, work places, and recreation areas; remove

brush, rock piles, junk, cluttered firewood, and potential

Blood-engorged flea (Xenopsylla

cheopis).

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Swollen lymph glands caused by

plague bacteria (bubonic plague).

Cats with plague can pass

the disease to their owners.

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A patient diagnosed

with suspected

plague should be

hospitalized and

medically isolated.

Laboratory tests

should be done,

including blood

cultures for plague

bacteria and

microscopic examination of lymph

gland, blood, and

sputum samples. Antibiotic treatment should begin as soon

as possible after laboratory specimens are taken. Streptomycin is the antibiotic of choice. Gentamicin is used when

streptomycin is not available. Tetracyclines and chloramphenicol are also effective. Persons who have been in close

contact with a plague patient, particularly a patient with

plague pneumonia, should be identified and evaluated. The

U.S. Public Health Service requires that all cases of suspected plague be reported immediately to local and state

health departments and that the diagnosis be confirmed by

CDC. As required by the International Health Regulations,

CDC reports all U.S. plague cases to the World Health

Organization.

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Attempts to eliminate fleas and wild rodents from the

natural environment in plague-infected areas are impractical. However, controlling rodents and their fleas around

places where people live, work, and play is very important

in preventing human disease. Therefore, preventive measures are directed toward reducing the risk of human

plague infection in those home, work, and recreational

settings where the risk of acquiring plague is high.

To protect against possible hantavirus

infection, scientists wear protective

suits when examining a mouse with

fleas that can harbor plague bacteria.