Contagious diseases

	Disease and synopsis of symptoms	Incubation period	Mode of transmission	Period of communicability

Actinomycosis
Chronic disease most frequently	Irregular; probably years	Contact from person to	Time and manner in which
	localized in jaw, thorax, or		after colonization in oral		person as part of normal		A. israelii  becomes part of
	abdomen; septicemic spread with		tissues, plus days or		oral flora.		normal flora is unknown.
	generalized disease may occur.		months after precipitating
	Lesions are firmly indurated areas		trauma and actual
	of purulence and fibrosis.		penetration of tissues.

Amebiasis
Infection with a protozoan parasite	Variation¾from a few days	Contaminated water or food	During period of cyst
	that exists in two forms: the		to several months or		containing cysts from		passing, which may
	hardy, infective cyst and the		years. Commonly 2 to 4		feces of infected persons,		continue for years.
	more fragile, potentially invasive		weeks.		often as complication of
	trophozoite. Parasite may act as a				another infection such as
	commensal or invade tissues,				shigellosis.
	giving rise to intestinal or
	extraintestinal disease.

Ascariasis (roundworm infection)
Helminthic infection of small	Worms reach maturity about	By ingestion of infective	As long as mature female
	intestine. Symptoms are variable,		2 months after ingestion		eggs from soil		worms live in intestine.
	often vague or absent, or		of embryonated eggs.		contaminated with human		Maximum lifespan of
	ordinarily mild; live worms,				feces containing eggs, but		adult worms is under 18
	passed in stools or regurgitated,				not directly from person		months; however, female
	are frequently first recognized				to person.		produces up to 200,000
	sign of infection.						eggs a day that can
							remain viable in soil for
							months or years.

Balantidiasis
Disease of colon characteristically	Unknown; may be only a	By ingestion of cysts from	As long as infection persists.
	producing diarrhea or dysentery		few days.		feces of infected hosts; in
	accompanied by abdominal colic,				epidemics, mainly by
	tenesmus, nausea, and vomiting.				fecally contaminated
					water.

Candidiasis (moniliasis, thrush,
	candidosis)
Mycosis usually confined to	Variable, 2 to 5 days in	Through contact with	Presumably for duration of
	superficial layers of skin or		thrush of infants.		excretions of mouth, skin,		lesions.
	mucous membranes with patients				vagina, and especially
	who have oral thrush, interterigo,				feces from patients or
	vulvovaginitis, paronychia, or				carriers; from mother to
	onychomycosis.				infant during childbirth;
					and by endogenous
					spread.

Carditis, Coxsackie (viral carditis,
	enteroviral carditis)
Acute or subacute myocarditis or	Usually 3 to 5 days.	Fecal-oral or respiratory	Apparently during acute
	pericarditis, which occurs as the				droplet contact with		stage of disease.
	only manifestation, or may				infected person.
	occasionally be associated with
	other manifestations.

Chickenpox, herb zoster
	 (varicella shingles)
Acute generalized viral disease with	From 2 to 3 weeks;	From person to person by	As long as 5 days but
	sudden onset of slight fever, mild		commonly 13 to 17 days.		direct contact, droplet, or		usually 1 to 2 days before
	constitutional symptoms, and a				air-borne spread of		onset of rash, and not
	skin eruption that is				secretion of respiratory		more than 6 days after
	maculopapular for a few hours,				tract of chickenpox cases		appearance of first crop of
	vesicular for 3 to 4 days, and				or of vesicle fluid of		vesicles.
	leaves a granular scab.				patients with herpes
					zoster.

Cholera
Acute intestinal disease with sudden	From a few hours to 5 days,	Through ingestion of food or	Thought to be for duration
	onset, profuse watery stools,		usually 2 to 3 days.		water contaminated with		of stool-positive stage,
	occasional vomiting, rapid				feces or vomitus of		usually only a few days
	dehydration, acidosis, and				infected persons or with		after recovery. Carrier
	circulatory collapse. Death may				feces of carriers.		stage may last for several
	occur within a few hours.						months.

Conjunctivitis, acute bacterial
Clinical syndrome beginning with	Usually 24 to 72 hours.	Contact with discharges	During course of active
	lacrimation, irritation, and				from conjunctivae or		infection.
	hyperemia of the palpebral and				upper respiratory tract of
	bulbar conjunctivae of one or				infected persons through
	both eyes, followed by edema of				contaminated fingers,
	lids, photophobia, and				clothing, or other articles.
	mucopurulent discharge.

Conjunctivitis, epidemic hemorrhagic 
	(Apollo 11 disease)
Virus infection with sudden onset of	1 to 2 days or even shorter.	Through direct or indirect	Unknown, but assumed to
	pain or sensation of a foreign				contact with discharge		be for period of active
	body in eye. Disease rapidly				from infected eyes and		disease, usually 1 to 2
	progresses (1 to 2 days) to full				possibly by droplet		weeks.
	case of swollen eyelids,				infection from those with
	hyperemia of the conjunctivae,				virus in throat.
	often with a circumcorneal
	distribution, seromucous
	discharge, and frequent
	subconjunctival hemorrhages.

Dermatophytosis
A. Ringworm of scalp and beard	10 to 14 days	Direct or indirect contact	As long as lesions are
	(tinea capitis, tinea kerion,				with articles infected with		present and viable fungus
	favus)				hair from humans or		persists on contaminated
Begins as small papule and spreads				infected animals.		materials.
	peripherally, leaving scaly
	patches of temporary baldness.
	Infected hairs become brittle and
	break off easily. Kerions
	sometimes develop.
B. Ringworm of nails (tinea	Unknown.	Presumably by direct	Possibly as long as infected
	unguium, onychomycosis)				extension from skin or		lesion is present.
Chronic infectious disease involving				nail lesions of infected
	one or more nails of hands or				persons. Low rate of
	feet. Nail thickens becoming				transmission.
	discolored and brittle with an
	accumulation of
	caseous-appearing material
	beneath nail.
C. Ringworm of groin and perianal	4 to 10 days.	Direct or indirect contact	As long as lesions are
	region (dhobie itch, tinea cruris)				with skin and scalp		present and viable fungus
D. Ringworm of the body (tinea				lesions of infected persons		persists on contaminated
	corporis)				or animals.		materials.
Characteristically appears as flat,
	spreading, ring-shaped lesions.
	Periphery is usually reddish,
	vesicular, or pustular and may be
	dry and scaly or moist and
	crusted.
E. Ringworm of the foot (tinea	Unknown.	Direct or indirect contact	As long as lesions are
	pedis, athlete's foot)				with skin lesions of		present and viable spores
Scaling or cracking of skin,				infected persons or		persist on contaminated
	especially between toes, or				contaminated floors or		materials.
	blisters containing this watery				shower stalls.
	fluid are characteristic. In severe
	cases vesicular lesions appear on
	various parts of body.

Diphtheria
Characteristic lesion marked by	2 to 5 days, sometimes	Contact with patient or	Variable, until virulent
	patch or patches of grayish		longer.		carrier; more rarely with		bacilli have disappeared
	membrane with surrounding dull				articles soiled with		from discharge and
	red inflammatory zone. Throat is				discharges from lesions of		lesions. Usual period is 2
	moderately sore in faucial				infected persons. Raw		to 4 weeks, but chronic
	diphtheria, with cervical lymph				milk has been a vehicle.		carriers may shed
	nodes enlarged and tender;						organisms for 6 months or
	occasionally swelling and edema						more.
	of neck.

Gastroenteritis, viral
A. Epidemic viral gastroenteritis	24 to 48 hours; in volunteer	Unknown; probably by	During acute stage of
Usually self-limited mild disease		studies with Norwalk		fecal-oral route. Several		disease and shortly
	that often occurs in outbreaks		agent range was 10 to 51		recent outbreaks strongly		thereafter.
	with clinical symptoms of		hours.		suggest food-borne and
	nausea, vomiting, diarrhea,				water-home transmission.
	abdominal pain, myalgia,
	headache, malaise, low-grade
	fever, or a combination thereof.
B. Rotavirus gastroenteritis	Approximately 48 hours.	Probably fecal-oral and	During acute stage of
	(sporadic viral gastroenteritis of				possibly respiratory		disease and later while
	infants and children)				routes.		virus shedding continues.
Sporadic severe gastroenteritis of						Virus is not usually
	infants and young children						detectable alter eighth day
	characterized by diarrhea and						of illness.
	vomiting, often with severe
	dehydration and occasional
	deaths.

Giardiasis (Giardia enteritis,
	lambliasis)
Protozoan infection principally of	In a water-home epidemic in	Localized outbreaks occur	Entire period of infection.
	upper small bowel; often		United States, clinical		from contaminated water
	asymptomatic, it may also be		illnesses occurred 1 to 4		supplies. By ingestion of
	associated with a variety of		weeks after exposure;		cysts in fecally
	intestinal symptoms such as		average 2 weeks.		contaminated water and
	chronic diarrhea, steatorrhea,				occasionally by fecally
	abdominal cramps, bloating,				contaminated food.
	frequent loose and pale, greasy,
	malodorus stools, fatigue, and
	weight loss.

Hepatitis, viral
A. Viral hepatitis A (infectious	From 15 to 50 days,	Person to person by	Studies indicate maximum
	hepatitis, epidemic hepatitis,		depending on dose;		fecal-oral route.		infectivity during latter
	epidemic jaundice, catarrhal		average 28-30 days.		Common-vehicle		half of incubation period,
	jaundice, Type A hepatitis)				outbreaks have been		continuing for a few days,
Onset is usually abrupt with fever, 				related to contaminated		after onset of jaundice.
	malaise, anorexia, nausea, and				water and food.
	abdominal discomfort, followed
	within a few days by jaundice.
B.Viral hepatitis B (Type B	Usually 45 to 160 days,	HBSAg, the infectious	From several weeks before
	hepatitis, serum hepatitis)	average 60 to 90 days.	agent, has been found in	onset of symptoms
Onset is usually insidious with	Variation is related in part	virtually all body	through clinical course of
	anorexia, vague abdominal	to amount of virus in	secretions, but only blood,	disease; carrier state can
	discomfort, nausea, and	inoculum, mode of	saliva, and semen have	last for years.
	vomiting, sometimes arthralgias	transmission, and host	been shown to be
	and rash, often progressing to	factors.		infectious. Transmission
	jaundice. Fever may be absent or	usually by percutaneous
	mild.	inoculation of infected
	blood and blood products;
	contaminated needles,
	syringes, and IV
	equipment.
C. Hepatitis, non-A, non-B (non-B	2 weeks to 6 months, model	Most common	Degree of immunity
	transfusion-associated hepatitis,		6 to 8 weeks.		posttransfusion hepatitis in		following infection is not
	hepatitis C)				United States and is more		known.
Chronic infection may be				common when paid
	symptomatic or asymptomatic.				donors are used.
	Differential diagnosis depends on				Percutaneous transmission
	exclusion of hepatitis types A and				documented and other
	B.				modes similar to those of
					hepatitis B virus arc
					suspected.

Herpangina; hand-foot-and-mouth
	disease, acute lymphonodular
	pharyngitis
Herpangina¾grayish	3 to 5 days for herpangina	Direct contact with nose and	During acute stage of illness
	papulovesicular pharyngeal		and hand-foot-and-mouth		throat discharges and		and longer because virus
	lesions on an erythematous base.		disease. Five days for		feces of infected (possibly		persists in stools for as
	Hand-foot-and-mouth		acute lymphonodular		asymptomatic) persons		long as several weeks.
	disease¾more diffuse oral		pharyngitis.		and by droplet spread.
	lesions on buccal surfaces of
	cheeks, gums, and tongue. Acute
	lymphonodular
	pharyngitis¾lesions are firm.
	raised, discrete, whitish to
	yellowish nodules.

Herpes simplex
Viral infection characterized by	2 to 12 days.	HSV Type 1: Direct contact	Secretion of virus in saliva
	localized primary lesion, latency,				with virus in saliva of		has been reported for as
	and a tendency to localized				carriers. HSV Type 2:		long as 7 weeks after
	recurrence. In perhaps 10% of				Sexual contact.		recovery from stomatitis.
	primary infections overt disease						Patients with primary
	may appear as illness of varying						lesions are infective for
	severity marked by fever and						about 7 to 12 days, with
	malaise lasting 1 week or more.						recurrent disease for 4
							days to 1 week.

Influenza
Acute viral disease of respiratory	Usually 24 to 72 hours.	By direct contact through	Probably limited to 3 days
	tract characterized by fever,				droplet infection; probably		from clinical onset.
	chilliness, headache, myalgia,				airborne among crowded
	prostration, coryza, and mild sore				populations in enclosed
	throat. Cough is often severe and				spaces.
	protracted.

Measles (rubeola, hard measles, 
	red measles, morbilli)
Acute, highly communicable viral	About 10 days varying from	By droplet spread or direct	From slightly before
	disease with prodromal fever,		8 to 13 days from		contact with nasal or		beginning of prodromal
	conjunctivitis, coryza, bronchitis,		exposure to onset of fever;	throat secretions of		period of 4 days after
	and Koplik's spots on the buccal		about 14 days until rash		infected persons. Measles		appearance of rash;
	mucosa. A characteristic red		appears; uncommonly		is one of most readily		communicability is
	blotchy rash appears on third to		longer or shorter human		transmitted communicable		minimal after second day
	seventh day, beginning on face,		normal immune globulin		diseases.		of rash.
	becoming generalized, lasting 4		(IG), given later than third
	to 7 days and sometimes ending		day of incubation period
	in branny desquamation.		for passive protection,
	Leukopenia is common.		may extend the incubation
			period to 21 days instead
			of preventing disease.

Meningitis, meningococcal
	(cerebrospinal fever,
	  meningococcemia)
Characterized by sudden onset of	Varies from 2 to 10 days,	By direct contact, including	Until meningococci are no
	fever, intense headache, nausea		commonly 3 to 4 days.		droplets and discharges		longer present in
	and often vomiting, stiff neck,				from nose and throat of		discharges from nose and
	and frequently a petechial rash				infected persons, more		throat. If organisms are
	with pink macules or, very				often carriers than cases.		sensitive to sulfonamides,
	rarely, vesicles. Delirium and						meningococci usually
	coma often appear; occasional						disappear from
	fulminating cases exhibit sudden						nasopharynx within 24
	prostration.						hours after institution of
							treatment. They are not
							fully eradicated from
							oronasopharynx by
							penicillin.

Meningitis, hemophilus (meningitis
	caused by Haemophilus influenzae)
Most common bacterial meningitis	Probably short¾within 2 to	By droplet infection and	As long as organisms are
	in children 2 months to 3 years		4 days		discharges from nose and		present, which may be for
	old in U.S. Otitis media or				throat during infectious		prolonged period even
	sinusitis may be precursor.				period. May be purulent		without nasal discharge.
	Almost always associated with				rhinitis. Portal of entry is
	bacteremia. Onset is sudden with				most commonly
	symptoms of fever, vomiting,				nasopharyngeal.
	lethargy, and meningeal
	irritation.

Mononucleosis, infectious (glandular
	fever, EBV mononucleosis)
Characterized by fever, sore throat	From 4 to 6 weeks.	Person-to-person spread by	Prolonged; pharyngeal
	(often with exudative				oropharyngeal route via		excretion may persist for
	pharyngotonsillitis), and				saliva. Spread may also		1 year after infection;
	lymphadenopathy (especially				occur via blood		15% to 20% of healthy
	posterior cervical). Jaundice				transfusion to susceptible		adults are oropharyngeal
	occurs in about 4% of infected				recipients.		carriers.
	young adults and splenomegaly in
	50%. Duration is from 1 to
	several weeks.

Mumps (infectious parotitis)
Acute viral disease characterized by	About 2 to 3 weeks,	By droplet spread and by	Virus has been isolated from
	fever, swelling, and tenderness of		commonly 18 days.		direct contact with saliva		saliva from 6 days before
	one or more salivary glands,				of an infected person.		salivary gland
	usually parotid and sometimes						involvement to as long as
	sublingual or submaxillary						9 days thereafter; but
	glands.						height of infectiousness
							occurs about 48 hours
							before swelling begins.
							Urine may be positive for
							as long as 14 days after
							onset of illness.

Paratyphoid fever
Frequently generalized bacterial	1 to 3 weeks for enteric	Direct or indirect contact	As long as infectious agent
	enteric infection, often with		fever; 1 to 10 days for		with feces or urine of		persists in excreta, which
	abrupt onset, continued fever,		gastroenteritis.		patient or carrier. Spread		is from appearance of
	enlargement of spleen, sometimes				is by food, especially		prodromal symptoms,
	rose spots on trunk, usually				milk, milk products, and		throughout illness, and for
	diarrhea, and involvement of				shellfish. Flies may be		periods up to several
	lymphoid tissues of mesentery				vectors.		weeks or months.
	and intestines.						Commonly 1 to 2 weeks
							after recovery.

Pediculosis (lice)
Infestation of head, hairy parts of	Under optimum conditions,	Direct contact with infected	Communicable as long as
	body, or clothing with adult lice,		eggs of lice hatch in 1		person and indirectly by		lice remain alive on
	larvae, or nits (eggs), which		week, reach sexual		contact with personal		infested person or in
	results in severe itching and		maturity in approximately		belongings, especially		clothing, and until eggs in
	excoriation of scalp or scratch		2 weeks.		clothing and head-gear.		hair and clothing have
	marks of body.				Crab lice are usually		been destroyed.
					transmitted through sexual
					contact.

The pneumonias
A. Pneumococcal pneumonia	Not well determined;	By droplet spread; by direct	Presumably until discharges
Acute bacterial infection		believed to be 1 to 3		oral contact or indirectly,		of mouth and nose no
	characterized by sudden onset		days.		through articles freshly		longer contain virulent
	with single shaking chill, fever,				soiled with respiratory		pneumococci in significant
	pleural pain, dyspnea, cough				organisms is common.		numbers. Penicillin will
	productive of "rusty" sputum and						render patient
	leukocytosis.						noninfectious within 24 to
							48 hours.
B. Mycoplasmal pneumonia	14 to 21 days.	Probably by droplet	Probably less than 10 days;
	(primary atypical pneumonia)				inhalation, direct contact		occasionally longer with
Predominantly afebrile lower				with infected person or		persisting febrile illness or
	respiratory infection. Onset is				with articles freshly soiled		persistence of the
	gradual with headache, malaise,				with discharges of nose		organisms in
	cough often paroxysmal, and				and throat from acutely ill		convalescence (as long as
	usually substernal pain (not				and coughing patient.		13 weeks is known).
	pleuritic). Sputum, scant at first,
	may increase later.
C. Pneumocystis pneumonia	Analysis of data from	Unknown.	Unknown.
	(interstitial plasma cell		institutional outbreaks
	pneumonia)		among infants indicates 1
Acute pulmonary disease occurring		to 2 months.
	early in life, especially in
	malnourished, chronically ill, or
	premature infants. Characterized
	by progressive dyspnea,
	tachypnea, and cyanosis; fever
	may not be present.
D. Chlamydial pneumonia	Not known, but pneumonia	Presumed to be vertically	Unknown, but length of
	(pertussoid eosinophilic		may occur in infants from		transmitted from infected		nasopharyngeal excretion
	pneumonia)		1 to 18 weeks of age		cervix to infant during		can be at least 2 months.
Subacute pulmonary disease		(more commonly between		birth, with resultant
	occurring in early infancy,		4 and 12 weeks).		nasopharyngeal infection.
	primarily in infants of mothers
	with infection of uterine cervix
	with causative organism.

Poliomyelitis (infantile paralysis)
Acute viral infection whose	Commonly 7 to 14 days for	Direct contact through close	Not accurately known. Cases
	symptoms include fever, malaise,		paralytic cases, with a		association. In rare		are probably most
	headache, nausea, vomiting, and		range from 3 to possibly		instances milk, foodstuffs.		infectious during first few
	stiffness of neck and back with or		35 days.		and other fecally		days after onset of
	without paralysis.				contaminated materials		symptoms.
					have been incriminated as
					vehicles. Fecal-oral is
					major route when
					sanitation is poor, but
					during epidemics and
					when sanitation is good,
					pharyngeal spread
					becomes relatively more
					important.
Respiratory disease (excluding
	influenza)
A. Acute febrile respiratory disease	From a few days to 1 week	Directly by oral contact or	For duration of active
Viral diseases of respiratory tract		or more.		by droplet spread,		disease; little is known
	are characterized by fever and				indirectly by hands or		about subclinical or latent
	one or more constitutional				other materials soiled by		infections.
	reactions such as chills or				respiratory discharges of
	chilliness, headache, general				infected person.
	aching, malaise, and anorexia; in
	infants by occasional
	gastrointestinal disturbances.
B. Common cold (acute coryza)			Presumably by direct oral
Acute catarrhal infections of upper				contact or by droplet
	respiratory tract characterized by				spread; indirectly by
	coryza, sneezing, lacrimation,				hands and articles freshly
	irritated nasopharynx, chilliness,				soiled by discharges of
	and malaise lasting 2 to 7 days.				nose and throat of infected
	Fever is uncommon in children				person.
	and rare in adults.

Rubella (German measles)
A. Congenital rubella	From 16 to 18 days, with a	Contact with nasopharyngeal	For about 1 week before and
Mild febrile infectious disease with		range of 14 to 21 days.		secretions of infected		at least 4 days after onset
	diffuse punctate and macular				person. Infection is by		of rash. Highly
	rash. Sometimes resembling that				droplet spread or direct		communicable. Infants
	of measles, scarlet fever, or both.				contact with patients and		with congenital rubella
	May be few or no constitutional				indirect contact.		syndrome may shed virus
	symptoms in children, but adults						for months after birth.
	may experience 1- to 5-day
	prodrome characterized by
	low-grade fever, headache,
	malaise, mild coryza, and
	conjunctivitis. As many as 20%
	to 50% of infections may occur
	without evident rash; overall 50%
	are not recognized.
B. Erythema infectiosum (fifth
	disease)
Mild nonfebrile erythematous
	eruption occurring as epidemics
	among children. Characterized by
	striking erythema of cheeks,
	reddening of skin, and lacelike
	serpiginous rash of body.
C. Exanthema subitum (roseola
	infantum)
Acute illness of probable viral cause
	characterized by high fever that
	suddenly appears and lasts 3 to 5
	days. A maculopapular rash on
	trunk and later on rest of body
	ordinarily follows lysis of fever.

Shigellosis (bacillary dysentery)
Acute bacterial disease primarily	1 to 7 days, usually 1 to 3	By direct or indirect	During acute infection and
	involving large intestine,		days.		fecal-oral transmission		until infectious agent is no
	characterized by diarrhea,				from patient or carrier.		longer present in feces,
	accompanied by fever, nausea,				Infection may occur after		usually within 4 weeks of
	sometimes vomiting, cramps, and				ingestion of very few		illness.
	tenesmus. In severe cases stools				organisms.
	contain blood, mucus, and pus.

Staphylococcal disease
A. Staphylococcal disease in	Variable and indefinite.	Major site of colonization is	As long as purulent lesions
	community, boils, carbuncles,		Commonly 4 to 10 days.		anterior flares.		continue to drain or
	furuncles, impetigo, cellulitis,				Autoinfection is		carrier state persists.
	abscesses, staphylococcal				responsible for at least
	septicemia, staphylococcal				one third of infections.
	pneumonia, osteomyelitis,				Person with draining
	endocarditis				lesion or any purulent
Staphylococci produce variety of				lesion or who is
	syndromes with clinical				asymptomatic (usually
	manifestations that range from				nasal) carrier of
	single pustule to impetigo to				pathogenic strain.
	septicemia to death. Lesion or				Air-home spread is rare.
	lesions containing pus are
	primary clinical finding, abscess
	formation is typical.
B. Staphylococcal disease in	Commonly 4 to 10 days but	Spread by hands of hospital	Same.
	hospital nurseries, impetigo,		may occur several months		personnel is primary mode
	abscess of breast		after colonization.		of transmission within
Characteristic lesions develop				hospitals, to a lesser
	secondary to colonization of nose				extent, air-borne.
	or umbilicus, conjunction,
	circumcision site, or rectum of
	infants with pathogenic strain.
C. Staphylococcal disease in	Variable and indefinite.	Major site of colonization is	As long as purulent lesions
	medical and surgical wards of		Commonly 4 to 10 days.		anterior nares.		continue to drain or
	hospitals				Autoinfection is		carrier state persists.
Lesions vary from simple furuncles				responsible for at least
	or stitch abscesses to extensively				one third of infections.
	infected bedsores or surgical				Person with a draining
	wounds, septic phlebitis, chronic				lesion or any purulent
	osteomyelitis, fulminating				lesion or who is an
	pneumonia, endocarditis, or				asymptomatic (usually
	septicemia.				nasal) carrier of a
					pathogenic strain.
					Air-borne spread is rare.

Streptococcal sore throat
Fever, sore throat, exudative	Short, usually 1 to 3 days,	Transmission results from	In untreated uncomplicated
	tonsillitis or pharyngitis and		rarely longer.		direct or intimate contact		cases 10 to 21 days; in
	tender anterior cervical lymph				with patient or carrier,		untreated conditions with
	nodes				rarely by indirect contact		purulent discharges,
					through objects or hands.		weeks or months.
					Nasal carriers are
					particularly likely to
					transmit diseases.

Syphilis, nonvenereal endemic
Acute disease of limited	2 weeks to 3 months.	Direct or indirect contact	Until moist eruptions of skin
	geographical distribution,				with infectious early		and mucous patches
	characterized clinically by				lesions of skin and		disappear¾sometimes
	eruption of skin and mucous				mucous membranes.		several weeks or months.
	membrane, usually without				Congenital transmission
	evident primary sore.				does not occur.

Trachoma
Communicable keratoconjunctivitis	5 to 12 days (based on	By direct contact with ocular	As long as active lesions are
	characterized by conjunctival		volunteer studies).		discharges and possibly		present in the conjunctivae
	inflammation with papillary				mucoid or purulent		and adnexal mucous
	hyperplasia, associated with				discharges of nasal		membranes.
	vascular invasion of cornea and				mucous membranes of
	in later stages by conjunctival				infected persons or
	scarring that may eventually lead				materials. Flies (Musca
	to blindness.				sorbens) may contribute to
					spread of disease.

Tuberculosis
Mycobacterial disease. Initial	From infection to	Exposure to bacilli in	As long as infectious
	infection usually goes unnoticed;		demonstrable primary		air-borne droplet nuclei		tubercle bacilli are being
	tuberculin sensitivity appears		lesion, about 4 to 12		from sputum of persons		discharged.
	within a few weeks; lesions		weeks. Whereas		with infectious
	commonly heal, leaving no		subsequent risk of		tuberculosis. Bovine
	residual changes except		progressive pulmonary or		tuberculosis results from
	pulmonary or tracheobronchial		extrapulmonary		exposure to tubercular
	lymph node calcification. May		tuberculosis is greatest		cattle and ingestion of
	progress to pulmonary		within 1 or 2 years after		unpasteurized dairy
	tuberculosis or, by		infection, it may persist		products.
	lymphohematogenous		for a lifetime as latent
	dissemination of bacilli, to		infection.
	produce miliary, meningeal, or
	other extrapulmonary
	involvement.

Typhoid fever (enteric fever,
	typhus abdominalis)
Systemic infectious disease	Depends on size of infecting	By food or water	As long as typhoid bacilli
	characterized by sustained fever,		dose; usual range 1 to 3		contaminated by feces or		appear in excreta; usually
	headache, malaise, anorexia,		weeks.		urine of patient or carrier.		first week throughout
	relative bradycardia, enlargement						convalescence; variable
	of spleen, rose spots on trunk,						thereafter. About 10% of
	nonproductive cough,						untreated patients will
	constipation more commonly than						discharge bacilli for 3
	diarrhea, and involvement of						months after onset of
	lymphoid tissues.						symptoms; 2% to 5%
							become permanent
							carriers.

Whooping cough (pertussis)
Acute bacterial disease involving	Commonly 7 days; almost	Primarily by direct contact	Highly communicable in
	tracheobronchial tree. Initial		uniformly within 10 days,		with discharges from		early catarrhal stage
	catarrhal stage has insidious onset		and not exceeding 21		respiratory mucous		before paroxysmal cough
	with irritating cough that		days.		membranes of infected		stage. For control
	gradually becomes paroxysmal,				persons by air-borne		purposes, communicable
	usually within 1 to 2 weeks, and				route, probably by		stage extends from 7 days
	lasts for 1 to 2 months.				droplets. Frequently		after exposure to 3 weeks
					brought into home by		after onset of typical
					older sibling.		paroxysms in patients not
							treated with antibiotics; in
							patients treated with
							erythromycin, period of
							infectiousness extends
							only 5 to 7 days after
							onset of therapy.