Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Hazard Analysis and Critical Control Points pro-

259

•

Each is found in specific geographic regions, and therefore is

spread by different rodent carriers. Further, each type of virus

causes a slightly different form of illness in its human hosts.

Hantaan virus is carried by the striped field mouse, and exists

in Korea, China, Eastern Russia, and the Balkans. Hantaan

virus often causes a severe form of hemorrhagic fever with

renal syndrome (HFRS).

Puumula virus is carried by bank voles, and exists in

Scandinavia, western Russia, and Europe. Puumula virus

causes a milder form of HFRS, usually termed nephropathia

epidemica.

Seoul virus is carried by a type of rat called the Norway

rat, and exists worldwide, but causes disease almost exclu-

sively in Asia. Seoul virus causes a form of HFRS which is

slightly milder than that caused by Hantaan virus, but results

in liver complications.

Prospect Hill virus is carried by meadow voles and

exists in the United States, but has not been found to cause

human disease. Sin Nombre virus, the most predominant

strain in the United States, is carried by the deer mouse. This

virus was responsible for severe cases of HPS that occurred in

the Southwestern United States in 1993. A similar, but geneti-

cally distinct strain was responsible for an outbreak of HPS in

Argentina in 1996, and was later termed the Andes virus.

During the outbreak in Argentina, five of the victims were

physicians, three of which were directly responsible for the

care of an HPS patient. This, along with additional epidemio-

logic evidence (such as the low rodent population density in

the area affected) suggest that person-to-person transmission

was possible during this outbreak, a feature unique to any

known hantavirus.

Black Creek Canal virus has been found in Florida. It is

predominantly carried by cotton rats. New York virus strain

has been documented in New York State. The vectors for this

virus appear to be deer mice and white-footed mice. Bayou

virus has been reported in Louisiana and Texas and is carried

by the marsh rice rat.

Blue River virus has been found in Indiana and

Oklahoma and seems to be associated with the white-footed

mouse. Monongahela virus, discovered in 2000, has been found

in Pennsylvania and is transmitted by the white-footed mouse.

Hantaviruses that produce forms of hemorrhagic fever

with renal syndrome (HFRS) cause a classic group of symp-

toms, including fever, malfunction of the kidneys, and low

platelet count. Because platelets are blood cells important in

proper clotting, low numbers of circulating platelets can result

in spontaneous bleeding, or hemorrhage.

Patients with HFRS have pain in the head, abdomen, and

lower back, and may report bloodshot eyes and blurry vision.

Tiny pinpoint hemorrhages, called petechiae, may appear on

the upper body and the soft palate in the mouth. The patient’s

face, chest, abdomen, and back often appear flushed and red, as

if sunburned. Around day eight of HFRS, kidney involvement

results in multiple derangements of the body chemistry.

Simultaneously, the hemorrhagic features of the illness begin to

cause spontaneous bleeding, as demonstrated by bloody urine,

bloody vomit, and in very serious cases, brain hemorrhages

with resulting changes in consciousness and shock.

Hantavirus pulmonary syndrome (HPS) develops in

four stages. They are: The incubation period. This lasts from

one to five weeks from exposure. Here, the patient may exhibit

no symptoms.

The prodrome, or warning signs, stage. The patient

begins with a fever, muscle aches, backache, and abdominal

pain and upset. Sometimes there is vomiting and diarrhea.

The cardiopulmonary stage. The patient slips into this

stage rapidly, sometimes within a day or two of initial symp-

toms; sometimes as long as 10 days later. There is a drop in

blood pressure, shock, and leaking of the blood vessels of the

lungs, which results in fluid accumulation in the lungs, and

subsequent shortness of breath. The fluid accumulation can be

so rapid and so severe as to put the patient in respiratory fail-

ure within only a few hours. Some patients experience severe

abdominal tenderness.

The convalescent stage. If the patient survives the res-

piratory complications of the previous stage, there is a rapid

recovery, usually within a day or two. However, abnormal

liver and lung functioning may persist for six months.

The diagnosis of infection by a hantavirus uses sero-

logic techniques. The ELISA(enzyme-linked immunosorbant

assay) is done in a laboratory to identify the presence of spe-

cific immune substances (antibodies), which an individual’s

body would only produce in response to the hantavirus. It is

difficult to demonstrate the actual virus in human tissue or to

grow cultures of the virus within the laboratory, so the major-

ity of diagnostic tests use indirect means to demonstrate the

presence of the virus.

Treatment of hantavirus infections is primarily support-

ive, because there are no agents available to kill the viruses

and interrupt the infection. The diseases caused by han-

taviruses are lethal. About 6–15% of people who contract

HFRS have died. Almost half of all people who contract HPS

will die. It is essential that people living in areas where the

hantaviruses exist seek quick medical treatment, should they

begin to develop an illness that might be due to a hantavirus.

Preventative measures focus on vector control (elimination of

rodents), and avoiding rodent infested areas.

See alsoEpidemics, viral; Epidemiology, tracking diseases

with technology; Epidemiology; Hemorrhagic fevers and dis-

eases; Virology

HAZARDANALYSIS ANDCRITICAL

CHazard Analysis and Critical Control Points program (HACCP)ONTROLPOINTS PROGRAM(HACCP)

Hazard Analysis and Critical Control Points (HACCP) refers

to a system that is established and instituted to monitor all

stages of a processing or manufacturing operation to ensure

that the final product is not compromised because of microbial

contamination. Originally, HACCP was devised for the food

processing industry. Now, HACCP has expanded to include

the manufacture of pharmaceuticals and other products that

could be affected by unwanted growth of microorganisms.

womi_H 5/6/03 3:20 PM Page 259