Prevention of disease transmission in a healthcare setting

Prevention of disease transmission in a health-care setting

by

Raymond B. Otero, Ph.D.

A. Introduction

The communicability of organisms responsible for transmitting diseases in humans depends on a variety of factors which will be explained throughout this publication. There are many terms that are utilized in understanding this aspect of microbiology. It is important that some of these terms are explained in the beginning. For example:

1. allergen - a chemical substance that elicits a hypersensitive response;

2. anaphylactic shock - an immediate sometimes fatal reaction that follow in a human or animal host by contact with the offending allergen through injection, ingestion or inhalation;

3. autogenous infection - infection derived from the patients own flora; similar to endogenous infection;

4. carrier - an individual who is colonized with a disease producing organism but shows no overt symptoms;

5. colonization - implies the presence of microorganisms either in or outside the host without causing any type of response in the host;

6. communicable - capable of being transmitted especially when referring to diseases;

7. contamination - presence of microorganisms that are transiently present on either a body surface or inaminate objects such as linens, water, food, etc.

8. dissemination - shedding of organisms into the environment host - the organism in or on which a parasite lives deriving its nutrients or energy from it (host);

9. endogenous infection - infection caused by an organism growing within a host’s body

10. epidemiology - study of the relationship of diseases- frequency and distribution;

11. flora - population of microorganisms inhabiting the internal and external surfaces of healthy humans or animals;

12. fomites - inaminate objects such as linens;

13. horizontal transmission - infections from one person to another;

14. immune response - a series of complicated reactions that may be beneficial in protecting the host from disease such as through vaccination or harmful causing injury to tissues or death such as in anaphylactic shock;

15. incubation period - the time interval that occurs during exposure to a disease producing organism and the initial stages of microbial disease; the interval of time may be from a few hours to many years.

16. infection - the replication of organisms in tissues of a human or animal host which may or may not develop into a clinical disease;

17. nosocomial infections - infections that are developed within a hospital or are produced by organisms acquired during hospitalization;

18. opportunistic infections - infections normally caused by microorganisms that are generally harmless but finds an opportunity to cause disease in an individual whose resistance is lowered by some type of underlying disease or Immunodeficiency;

19. parasite - an organism that lives on or in another and obtains its nutrients from it;

20. parenteral route - introduction of substances by intravenous, subcutaneous, intramuscular or intramedullary injection.

21. pathogenic organisms - disease producing organisms;

22. reservoir of infection - living or nonliving material in or on which an infectious agent multiplies and or develops and is dependent for its survival in nature;

23. septicemia - disease caused by the spread of organisms and their enzymes and toxins via circulating blood;

24. source of infection - location from which an infection is acquired;

25. standard precautions - term developed by the Centers for Disease Control and Prevention on handling all body fluids as infectious regardless of source;

26. vector - an agent or a living organism such as an insect that can transmit disease producing organisms from one host to another;

27. vertical transmission - infections spread from mother to fetus.

B. Modes of Transmission

The communicability of infections is dependent on the accessibility of the reservoir and routes that are available for transmission. There are a variety of ways organisms can enter a human host. For example, viruses like influenza commonly enter by the respiratory route, organisms like Shigella dysenteriae enter by the gastrointestinal route, Staphylococcus aureus by breaks in skin or mucous membranes, malaria by biological vectors such as the mosquito and hepatitis B by the parenteral route.

Some organisms may have more than one way of entering a host. Organisms such as Mycobacterium tuberculosis primarily enter by the airborne route by creating small droplet nuclei (particles the size of <5 micrometers) that can enter very easily into the lung. The mumps virus can enter by way of droplet spread or direct contact with saliva of an infected individual. Hepatitis B virus can enter by the parenteral, sexual or vertical route. Salmonella typhi is spread by contaminated food through human sewage such as oysters, or by fecally contaminated water which is in both cases generally referred to as common-vehicle transmission. Malaria is transferred by the bite of an infective female (Anopheles) mosquito which is referred to as vectorborne transmission. It is important to note here that there are at least two ways vectors can transmit disease to humans: biologically, where the vector is used as part of the life cycle in reproduction such as in malaria, and mechanical where there is physical transference of organism by an insect such as flies from fecal contamination obtained from landfills or sewer drainage.

Knowing how organisms are transferred to the human host is helpful in determining how nosocomial infections occur. This information can lead to the source of the problem and may give rise to specific control measures. For example, when one observes that in a particular ward in a nursing home setting has a very alarming number of urinary tract infections caused by enteric organisms such as Escherichia coli or Proteus mirabilis or Enterococcus faecalis, one would expect poor hygiene or lack of perineal cleansing among the residents. The staff development person observing this data would stress to the nursing staff the need for better hygienic behavior among the residents (See Figures 1 and 2).

Table 1 is a compilation of known endogenous flora that can be normally isolated from humans without expression of any clinical signs. It is so important to realize that the human host’s own flora could cause infections especially when the patient is compromised immunologically such as in cancer or AIDS. Remember that the human host can become colonized with organisms that are known to cause disease (pathogenic). It is not unusual to isolate these organisms from specimens that are submitted for microbiological analysis. Sometimes, unfortunately, patients are treated for colonization rather than infection. When this occurs the health-care facilities are creating "super bugs" which makes the use of antibiotics less effective.

Table 1 - Endogenous flora as potential pathogens¹

Organism	Normal location	Frequency	Mode of transmission	Common infections
Gram positive
1. Staphylococcus aureus	skin, hair, axilla, perianal, anterior nares, mouth	common	contact, rarely airborne or through fomites	skin lesions, abscesses
2. Staphylococcus epidermidis	skin, hair, nasopharnyx, mouth, vagina	very common	contact	skin lesions, prosthetic contamination
*3. Streptococcus pyogenes* (Group A)**	orapharynx, perianal, anal	uncommon (5 - 10%)	contact, rarely airborne or through fomites	pharyngitis
*4. Streptococcus* agalactiae (Group B)**	adult vagina, genitalia, colon	uncommon (10 - 30% of pregnant females	contact	neonatal meningitis
5. Enterococcus faecalis	colon	common	contact²	urinary tract infection, endocarditis
6. Streptococcus pneumoniae	oropharynx	uncommon (<25%)	droplet spread, direct oral contact	pneumonia, otitis media
*7. Streptococcus* sp.**	oropharynx, skin	very common	contact	endocarditis
8. Corynebacterium sp.	skin, mouth, vagina	very common	contact	endocarditis

Yeasts
1. Candida albicans	mouth, skin, vagina, colon	common	contact	mucocutaneous
*2. Candida* sp.**	mouth, skin, vagina	common	contact	mucocutaneous

Gram negative
1. Escherichia coli	colon, perineum	very common	contact	urinary tract infections, wounds
2. Klebsiella pneumoniae	colon, perineum	common	contact	urinary tract, pneumonia
3. Proteus mirabilis	colon, perineum	common	contact	urinary tract infections, wounds
*4. Serratia* sp.**	colon, perineum	uncommon	contact, environmental	urinary tract infections, wounds, pneumonia
5. Pseudomonas aeruginosa	colon	uncommon (less than 10% of population are colonized)	contact, environmental³	urinary tract infections, wounds and pneumonia (especially in cystic fibrosis patients
6. Hemophilus influenzae	oropharynx	common (as high as 50% of the population - non-type b strains)	contact	meningitis, pneumonia
7. Neisseria meningitis	oro- or nasopharynx	uncommon (5 - 10%)	close contact such as mouth to mouth	meningitis

Anaerobic bacteria

*1. Bacteriodes* sp.**	colon, vagina	very common	contact	septicemia
*2. Clostridium* sp.**	colon, vagina	common	contact	septicemia
3. Fusobacterium sp.	colon, upper respiratory	common	contact	septicemia

Molds	ubiquitous	disease due to compromising conditions	airborne	pneumonia

Viruses	>400 are classified; role as endogenous flora is undetermined		airborne	variety

^{1References:

Manual of Clinical Microbiology. P. R. Muray, et. al. American Ssociety of
Microbiology. 6^th edition. 1995.
Control of Communicable Diseases Manual. A. S. Benenson, Editor. American Public Health
Association. 17^th edition. 1995.

^{2vehicle - rectal thermometers
^{3Hot tubs, whirlpools, tap water, eye drops, soil, irrigation fluids, soaps,
dialysis equipment, shower heads

Figure 1 - Example of a Urine Microbiology Report

Source: Clean catch urine sample

Status: final

Isolate #1: > 100,000 CFU¹ Escherichia coli}}}

Antibiotic	MIC²	Interpretation

Ampicillin	2	S³
Carbenicillin	< 16	S
Ceftriaxone	< 8	S
Cephalothin	4	S
Ciprofloxacin	< 0.5	S
Gentamicin	< 0.5	S
Nitrofurantoin	< 32	S
Norfloxacin	< 4	S
Tetracycline	< 1	S
Tobramycin	< 0.5	S
Trimethoprim-sulfamethoxazole	< 10	S

^{1Colony forming units = number of colonies counted on a plate
^{2Minimal inhibition concentration - the concentration of the antibiotic that
inhibits the growth of the organism, generally in micrograms.
^{3S = susceptible (R if present would = resistant)

Escherichia coli is normally found in the colon (See Table 1).
This organism is the most common cause of urinary tract infections especially in the
elderly.

The three most common isolates of urinary tract infections are Escherichia coli,
Proteus mirabilis and Enterococcus sp. If a nurse examines this
report which was either compiled by the laboratory or the person doing the
surveillance, would quickly see that there are increasing numbers of these isolates over
time. This indicates that there is a major problem with urinary tract infections - they
are continually rising over time. Since these organisms are normally found in the
intestine (See Table 1), the probability that hygiene of
patients/residents is suspect. Knowing the source of organisms can contribute to
reduction, prevention and/or control of infections.

As mentioned above there are a variety of ways microorganisms can enter a human host:
contact, airborne, common vehicle and vector-borne. Contact transmission is divided into
two sub-groups: direct contact which involves direct body surface-to-body surface contact
which allows the physical transfer of organisms from one person to another and indirect
contact which involves contact of a susceptible host with a contaminated object (usually
fomites) such as contaminated instruments, dressings or

grossly contaminated linens or even gloves that are not changed from one site to
another from the same patient ( e.g., perineal cleansing and G-tube examination).

Airborne transmission occurs when organisms are spread by droplet nuclei (< 5
micrometers or smaller in diameter) of evaporated droplets containing microorganisms that
will remain suspended in the air for prolonged periods of time especially when there is
improper ventilation.

Common vehicle transmission applies when microorganisms are transmitted by contaminated
food, water, medications, devices and equipment. Foodborne illnesses are

becoming more prevalent in the United States especially with Escherichia coli
0157:H7

(See Figure 3).

Vector-borne transmission occurs when vectors such as mosquitoes, or ticks infect
humans directly.

Sometimes rats or other vermin act as reservoirs for organisms that infect humans or
animals such as the Hantaviruses. Fortunately, this method of transmission is rare in the
United States.

Table 2 list the common pathogenic organisms, sites of infection,
the typical disease(s) they produce, incubation periods, modes of transmission and
precautionary methods for prevention. The Centers for Disease Control and Prevention
proposed in 1996 new terminology for transmission-based precautions designed for
patients/residents known or suspected to be infected with highly transmissible or
epidemiologically important pathogens for which additional precautions beyond Standard
Precautions (formerly Universal Precautions) are needed to interrupt transmission in a
healthcare setting regardless of type.

There are three types of transmission-based precautions:}}}

a. airborne precautions

b. droplet precautions

c. contact precautions

Airborne precautions are designed to reduce the risk of airborne transmission of infectious agents such as Mycobacterium tuberculosis which creates small particles of <5 micrometers or less. This microorganism can be easily carried by air currents and may become inhaled. Special ventilation systems must be employed to prevent this from happening (special rooms with air-exchanges and negative pressures).

Droplet precautions involves contact of the conjunctivae, or mucous membranes of the nose or mouth of a particle usually > 5 micrometers in diameter. Droplets are generated from the source person during coughing, sneezing, or suctioning. Transmission by this route requires close contact (3 feet or less). Since these droplets are large, they do not remain suspended in the air for long periods of time.

Contact precautions is designed to reduce the spread of organisms by direct or indirect contact. Direct contact transmission involves skin to skin contact such as turning a patient/resident. Sometimes the environment can contribute to such contamination (Clostridium difficile or Enterococcus faecalis). If a particular patient/resident is incontinent and contamination of the environment is likely, then a private room is generally used. Often patients/residents are placed in contact isolation if they are either infected or colonized with an epidemiologically important organism such as Methicillin-resistant Staphylococcus aureus or vancomycin-resistant Enterococcus sp. Private rooms are commonly used for contact isolation. Ventilation systems are not required in such rooms.

Table 2 - Common pathogenic organisms and modes of transmission¹

Organism	Site(s)	Disease(s)	Incubation period	Mode of transmission/ precautions
Gram positive
1.Corynebacterium diphtheriae	throat	diphtheria	2-5 days	contact/droplet spread
2. Streptococcus pneumoniae	lower respiratory tract	pneumonia, meningitis	1-3 days	contact/droplet spread
3. Listeria monocytogenes	meningoencephalitis	listeriosis	3-70 days	ingestion of raw or contaminated milk, soft cheeses, contaminated vegetables/standard
4. Bacillus anthracis	lower respiratory tract, skin lesions	anthrax	few hours - 7 days	contact with tissues of infected animal or products (i.e., hides, wool - occupational); ingestion of uncooked meats contaminated with organism/standard
5. Staphylococcus aureus	skin , osteomyelitis, blood, heart	boils, furuncles, abscesses, impetigo, osteomyelitis, sepsis, toxic shock syndrome	4-10 days	contact, autoinfection/ major lesions or drug resistant - contact
6. Streptococcus pyogenes	throat, skin, blood, middle ear	pharyngitis, septicemia, erysipelas, rheumatic fever, scarlet fever, otitis media, foodborne illness	short, usually 1 - 3 days	direct contact/droplet spread
Gram negative
1. Bordetella pertussis	oropharynx	whooping cough	6-20 days	direct contact with discharges from respiratory mucous membranes of infected persons by the airborne route/droplet spread
2. Escherichia coli (O157:H7)	large intestine	hemorrhagic colitis	3-8 days	ingestion of undercooked hamburger/standard
3. Legionella sp.	lower respiratory tract	legionellosis	2-10 days	airborne (environmental, non-communicable)
4. Neisseria gonorrhoeae	genitourinary tract, eye	gonorrhoea, pelvic inflammatory disease, septicemia, pharyngitis	2-7 days	sexual (standard precautions)
5. Neisseria meningitidis	meninges	meningitis	2-10 days	direct contact/ droplet spread
6. Salmonella sp.	small intestine	gastroenteritis	6-72 hours	ingestion/contact²
7. Salmonella typhi	small intestine	typhoid fever	1-3 weeks	ingestion/ standard²
8. Shigella sp.	large intestine	shigellosis (enteritis); bacterial dysentery	1-3 days	ingestion/ standard²
9. Yersinia sp.	large intestine	enterocolitis, acute mesenteric lymphadenitis	3-7 days	ingestion/ standard²
10. Vibrio sp.	large intestine	cholera, enteritis	2-3 days	ingestion/ standard²
Anaerobes
Gram positive anaerobes
1. Actinomycetes sp.	jaw, thorax, abdomen	chronic abcesses, draining sinuses	irregular, probably many years	endogenous
2. Clostridium botulinum	acute bilateral cranial nerve impairment	botulism	12-36 hours	ingestion of pre-formed toxin (non-communicable)
3. Clostridium difficile	large intestine	pseudomembranous colitis		environmental/contact
4. Clostridium perfringens	skin lesion, large intestine	gas gangrene, food poisoning	food poisoning 6-24 hr; gas gangrene 1-4 days	skin lesions, ingestion (non-communicable)
5. Clostridium tetani	nerve - muscular contractions	tetanus	3-21 days	lesions (non-communicable)

Gram negative anaerobes
1. Bacteriodes sp.	large intestine	peritonitis, endometritis, abscesses, septicemia	unknown	endogenous
Acid-fast
1. Mycobacterium tuberculosis	lower respiratory tract, laryngeal, meningeal	tuberculosis	4-12 weeks	airborne (small particles <5um in diameter)/airborne
2. Mycobacterium avium complex	lower respiratory tract, lymph nodes	pulmonary, lymphadenitis	unknown	ingestion, skin lesions (non-communicable)
Yeasts
1. Candida albicans	mucocutaneous, skin	oral thrush, intertrigo, vulvovaginitis, paronychia	variable - 2-5 days in infants	endogenous (sexual), contact, neonatal (mother)/standard
2. Cryptococcus neoformans	meningeal, lower respiratory tract	meningitis, pneumonia	unknown	respiratory (inhalation), environmental, (non-communicable)
Molds
1. Aspergillus sp.	lower respiratory tract	aspergillosis	few days to as many weeks	airborne (non-communicable)
2. Blastomyces dermatitidis	lower respiratory tract, skin	blastomycosis	indefinite, few weeks or less to months	airborne (non-communicable)
3. Coccidioides immitis	lower respiratory tract, skin	coccidioidomycosis	1-4 weeks	airborne (non-communicable)
4. Histoplasma capsulatum	lower respiratory tract, skin,	histoplasmosis	3-17 days	airborne (non-communicable)
Viruses
1. Acquired immunodeficiency syndrome	prgressive damage to immune and other organ systems, including CNS	AIDS	HIV infection to AIDS is from 1 year to 10 years or longer	sexual and exposure to blood or tissues/standard
2. Chicken pox/Varicella	skin	chicken pox	13-17 days	airborne/airborne
3. Hepatitis A	liver	hepatitis	28-30 days	oral/standard
4. Hepatitis B	liver	hepatitis	60-90 days	percutaneous and permucosal/standard
5. Hepatitis C	liver	hepatitis	6-9 weeks	blood transfusions/standard³
6. Herpes simplex I	skin	herpes (vescicular lesions)	2-12 days	contact/standard
7. Herpes simplex II	skin	herpes (genital)	2-12 days	contact/standard
8. Herpes Zoster	skin	shingles	13-17 days	airborne/contact⁴
9. Influenza	lower respiratory tract	flu	1-3 days	airborne/droplet spread
10. Rubella	skin/generalized	German measles	14-23 days	droplet spread
11. Rubeola	skin/generalized	measles	7-18 days	droplet spread

__________________________

Note: Regardless of the situation, Standard Precautions is always in place; a private room maybe dependent on age, patient’s hygienic behavior, type of organism, and drainage containment.
^1References:
1. Control of Communicable Diseases Manual. A. S. Benenson, editor. 16^th edition. 1995.

2. Diseases. Springhouse. 1996.

3. Mosby’s Handbook of Diseases. R. Langford and J. M. Thompson. Mosby. 1996.
^{2Use contact precautions for diapered or incontinent children less than 6 years
and for duration of illness.
^{3Diapered or incontinent patients use contact precautions.
^{4Airborne precautions in immunocompromised patients.

C. Work restriction guidelines for the healthcare worker

A written policy for restricting healthcare workers who are ill should be developed for
all healthcare facilities regardless of level of care. This policy should be presented at
orientation of all new employees and again reemphasized throughout employment. The policy
so written should also have persons listed who have the responsibility to restrict the
health-care worker from having direct contact with patients/residents. Table
3 lists some of the common diseases of personnel in healthcare, whether they should be
released from patient/resident contact, if partial work restriction should be in place and
finally the duration of time for this restriction. Prevention of disease in a healthcare
environment is not always limited to barrier control of the patient or resident. At times,
the health-care worker can give his/her sickness to the patient or resident by not
following their own advice.

Table 3 - Work restrictions for personnel in health-care with communicable
diseases¹}}}

Disease	Relieve from direct resident contact	Partial work restriction	Duration
Conjunctivitis	Yes		Until discharges cease
Cytomegalovirus infections	No
Diarrhea Acute stage	Yes		*Until symptoms and infection with Salmonella* has been ruled out**
Diarrhea Convalescent stage (nontyphoidal)	No	High-risk residents only	Until stool is free of the infecting organism on two consecutive cultures not less than 24 hours apart
Other enteric pathogens²	No
Enteroviral infections	No	Personnel should not take care of infants	Until symptoms resolve
Hepatitis A	Yes		Until after onset of jaundice
Hepatitis B, acute	No	Proper barriers such as gloves for procedures that involve trauma to tissues or contact with mucous membranes or non-intact skin³	Until antigenemia resolves
Chronic antigenemia	No	Same as acute illness	Until antigenemia resolves
Hepatitis C	No	Same as hepatitis B
Hepatitis D	No	Standard Precautions
Hepatitis E	No	Standard Precautions
Herpes Simplex - genital	No
Herpes Simplex - skin lesions (herpetic whitlow)	Yes	Gloves may not prevent transmission	Until lesions heal
Herpes, orofacial	No	High risk residents only	Until lesions heal
HIV-Ab +	No		Facility’s policy on exposure-prone procedures should be evaluated
Measles - active	Yes		Until 7 days after the rash appears
Measles - post exposure susceptible personnel	Yes		From the 5^th through the 21^st day after exposure and/or 7 days after the rash appears
Mumps - active	Yes		Until 9 days after onset of parotitis
Mumps - postexposure (susceptible personnel)	Yes		From the 12^th through the 26^th day after exposure or until 9 days after onset of parotitis
Pertussis - Active	Yes		From the beginning of the cararrhal stage through the 3^rd week after onset of paroxysms or until 7 days after start of effective therapy⁴
Pertussis - postexposure (asymptomatic)	No
Pertussis - postexposure (symptomatic)	Yes		Same as active pertussis
Rubella - active	Yes		Until 5 days after the rash appears
Rubella -postexposure (asymptomatic personnel)	Yes		From the 7^th day through the 21^st day after exposure and/ or 5 days after rash appears
Scabies	Yes		Until properly treated⁵
Staphylococcus aureus (skin lesions)	Yes		Until lesions have resolved⁶
Streptococcus pyogenes (Group A)	Yes		Until 24 hours after adequate treatment is started⁷
Tuberculosis - pulmonary	Yes		After adequate therapy has been given⁸, three consecutive daily acid-fast smears are negative and no cough
Upper respiratory tract infections	yes	High risk patients such as neonates, or residents with chronic obstructive pulmonary disease	Until acute symptoms have resolved
Zoster - shingles (active)	No	Proper barriers - should not care for high risk residents	Until lesions are dry and crusted
Zoster - shingles - (postexposure asymptomatic personnel)	Yes		From the 10^th through the 21^st day after exposure or if varicella occurs, until all lesions dry and crusted

^{1From: Modified from APIC: Infection Control and Applied Epidemiology. Principle
and Practice. Mosby. Pp. 21-5 to 21-7. 1996 and Immunization of Health-care workers, MMWR.
Volume 46/No. RR-18. 1997.
^{2Good personal hygiene such as handwashing before and after all patient/resident
contact.
^{3Standard Precautions.
^{4Antibiotic of choice is erythromycin.
^{5Close supervision of treatment and bathing is recommended. Itching may persist
for 1 - 2 weeks and it should not be regarded as a sign of drug failure or reinfestation.
^{6Susceptibility testing must be performed to determine treatment course.
^{7Penicillin is the primary drug of choice, erythromycin is secondary.
^{8One can not rely on a certain period of time for therapy, i.e., 2 weeks of
medication; negative smears and an improvement of clinical symptoms are important.

D. Immunization of health-care workers

According to the Centers for Disease Control and Prevention, maintenance of immunity is
an essential part of prevention and infection control programs for health-care workers
(MMWR, 46/No. RR-18, 1997). All health-care workers having contact with patients or
residents are at risk for exposure to and possible transmission of vaccine-preventable
diseases. Regardless of the type of health-care facility, there is a specific need for a
comprehensive immunization policy for all health-care workers. Table 4
lists the immunizing agents that are strongly recommended for health-care worker.

Table 4 - Immunizing agents and schedules for health-care workers(HCWs)¹}}}}}}}}

Immunizing agent	Primary schedule and boosters
Hepatitis A vaccine²	Two doses of vaccine either 6-12 months apart.
Hepatitis B (recombinant ) vaccine³	Two doses IM 4 weeks apart; third dose 5 months after second; booster doses not necessary.
Influenza vaccine (inactivated whole-virus and split-virus vaccines)⁴	Annual vaccination with current vaccine. Administered IM.
Measles live-virus vaccine⁵	One dose SC; second dose at least 1 month later.
Mumps live-virus vaccine⁶	One dose SC; no booster.
Pneumococcal polysaccharide vaccine (23 valent)⁷	One dose, 0.5 ml, IM or SC; revaccination recommended for those at highest risk >5 years after the first dose.
Rubella live-virus vaccine⁸	One dose SC; no booster.
Tetanus and diphtheria toxoids vaccine⁹	Two IM doses 4 weeks apart; third dose 6-12 months after second dose; booster every 10 years.
Varicella-zoster vaccine¹⁰	Two 0.5 ml doses SC 4-8 weeks apart if > 13 years of age.

^{1From: Immunization of Health-care workers. MMWR. December 26, 1997. 46/No.RR-18.
^{2Not routinely indicated for HCWs in the United States. Persons who work with
HAV-infected primates or with HAV in a research laboratory setting should be vaccinated.
The safety of the HAV vaccine in pregnant women has not been determined.
^{3On the basis of limited data, no adverse effects to developing fetuses is
apparent. Pregnancy should not be considered a contraindication to vaccination of women.
The vaccine produces neither therapeutic nor adverse effects on HBV infected persons.
Prevaccination serologic screening is not indicated for persons being vaccinated for
occupational risk.
^{4HCWs who have contact with patients at high risk for influenza or its
complication; HCWs who work in chronic care facilities; HCWs who work with high-risk
medical conditions or who are aged >65 years. No evidence of risk to mother or
fetus when the vaccine is administered to a pregnant woman with an underlying high risk
condition. The vaccine is recommended during the 2^nd and 3^rd
trimesters of pregnancy because of increased for hospitalization.
^{5HCWs born during or after 1957 who do not have documentation of having received
two doses of live vaccine on or after the 1^st birthday or a history of
physician-diagnosed measles or serologic immunity should be vaccinated. Vaccination should
be considered for all HCWs who lack proof of immunity, including those born before 1957.
^{6HCWs believed to be susceptible can be vaccinated. Adults born before 1957 can
be considered immune.
^{7Adults who are at increased risk of pneumococcal disease and its complications
because of underlying health conditions; older adults especially those age >65
who are healthy. The safety of the vaccine in pregnant woman has not been evaluated. It
should not be administered during pregnancy unless the risk of infection is high. Previous
recipients of any type of pneumococcal vaccine who are at highest risk for fatal infection
or antibody loss may be revaccinated >5 years after first dose.
^{8Indicated for HCWs, both men and women, who do not have documentation of having
received live vaccine on or after 1^st birthday or laboratory evidence of
immunity. Adults born before 1957, except woman who can become pregnant, can be considered
immune. The risk for rubella-vaccine associated malformations in the offspring of women
pregnant when vaccinated, or who become pregnant within 3 months after vaccination is
negligible. Such women should be counseled regarding the theoretical basis of concern for
the fetus.
^{9All adults. Except in the 1^st trimester, pregnancy is not a
precaution.
^{10Indicated for HCWs who do not have either a reliable history of varicella or
serologic evidence of immunity. Because 71% - 93% of persons without a history of
varicella are immune, serologic testing before vaccination is likely to be cost-effective.
All healthcare workers, i.e., medical or nonmedical, paid or volunteer, full time or
part-time, student or nonstudent, with or without patient-care responsibilities who work
in health-care institutions, i.e., inpatient and outpatient, public and private, should be
immune to measles, rubella and varicella.

E. Summation

Recognition of the epidemiology of diseases by health-care workers is important for a
variety of reasons. The primary one of course is to prevent the transmission of organisms
to their patients or to themselves. But also understanding how organisms are transmitted
can reduce anxiety levels. To often health-care facilities over isolate which causes
emotional distress to the patient/resident and to their families as well as to visitors
and other patients/residents and their visitors. Presentations on this very subject should
be given during employee orientation and reinforced during employment. Health-care cost as
everyone knows has sky rocketed to a point that many can not afford health insurance. All
of us can help in the reduction of health-care cost by decreasing infections among
patients and protecting ourselves against vaccine-preventable diseases.}}}}}}}}}}