includes  excessive  bleeding  at  venipuncture  sites, the nose, and gums. Tissue is easily bruised. In some  patients,  after  a  few  days  of  fever,  their  con- dition deteriorates into sudden shock (known as the  dengue  shock  syndrome)  with  blotchy  cool skin,  cyanosis  around  the  mouth,  rapid  pulse,  and abnormally  low  blood  pressure.  In  untreated  cases of  the  dengue  shock  syndrome,  the  fatality  may be  as  high  as  40  to  50  percent. Outbreaks of dengue hemorrhagic fever have been  reported  throughout  Southeast  Asia  and Cuba.  The  occurrence  is  during  the  wet  season when  the  Aedes  aegypti  population   is   highest. About a third of all deaths are under 15 years of age. This disease primarily affects the indigenous population. The  infectious  agent  is  the  dengue  virus  (types 1, 2, 3, and 4). The reservoir is  Aedes  aegypti  mos- quito  and  man,  and  it  is  transmitted  by  a  mos- quito bite. The disease is believed to occur by an immunological  reaction  from  a  second  or  subse- quent  infection  with  the  dengue  virus.  See  the Dengue  Fever  section  for  method  of  control. Giardiasis Giardiasis is a parasitic infection of the small intestine.  Symptoms  may  include  chronic  diar- rhea, excess fat in the stools, abdominal cramps, bloating, frequent loose pale stools, fatigue, and weight loss. The diagnosis is established by iden- tification  of  cysts  or  trophozoites  in  feces. Giardiasis  occurs  worldwide  and  in  children more  often  than  in  adults.  More  cases  occur  in areas with poor sanitation, in institutions, and in day-care  centers.  Waterborne  outbreaks  have  been frequently seen in the United States. The infectious agent is  Giardia  lamblia,  a pro- tozoa. Reservoirs include man, beavers, and other wild  or  domestic  animals. Local outbreaks occur when the cysts are in- gested with contaminated water and less often in fecally contaminated food. Transmission may oc- cur from person to person by the fecal-oral route in day-care centers. The  incubation  period  ranges  from  5  to  25 days.   Giardiasis   is   communicable   during   the period  of  infection;  undiagnosed  carrier  states  are common.  Treat  the  infection  as  directed  by  a  med- ical  officer.  Quinicrine  hydrochloride  (Atabrine) or  metronidazole  (Flagyl)  are  drugs  of  choice. Preventive  measures  for  control  include  (1) filtering of public water supplies suspected to be at risk from human or animal fecal contamination; (2)  ensuring  that  families,  inmates,  and  personnel concerned with institutions and day-care centers receive training in personal hygiene after defeca- tion; and (3) ensuring that emergency water sup- plies taken from suspected sources are boiled or treated  with  chlorine  or  iodine. Management  of  patients,  contacts,  and  the nearby  environment  include  (1)  enteric  precau- tions  for  patients  and  (2)  investigating  contacts and the environment for the source of infections. There  is  no  requirement  for  quarantine. Epidemic  measures  include  investigating  cases to  determine  a  common  source,  such  as  water, food, or direct contact, and instituting measures to  prevent  transmission. Viral Hepatitis Several  different  illnesses  are  considered  as viral  hepatitis;   they  have  similarities  and  dif- ferences. This section will discuss the two major types. VIRAL   HEPATITIS   A.—   The  onset  is gradual  over  several  days  with  symptoms  of  fever, malaise,  loss  of  appetite,  nausea,  abdominal discomfort,  and,  a  few  days  later,  jaundice.  The course of this disease varies from the commonly seen mild form (lasting for 1 to 2 weeks) to the uncommonly  seen  severe  form  (lasting  several months).  A  convalescence  of  several  weeks  can be expected. Complete recovery without sequelae can  be  expected.  Many  cases  are  mildly  symp- tomatic  with  no  jaundice.  Viral  hepatitis  A  oc- curs  worldwide  in  epidemics  and  is  endemic  in many  developing  countries.  Many  outbreaks  oc- cur in institutions, housing areas, and in military forces,  This  disease  is  more  common  in  school- age  children  and  young  adults. The infectious agent is the hepatitis A virus. The  reservoir  is  man.  The  average  incubation period  is  about  28  to  30  days,  but  it  will  range from 15 to 50 days, depending on the virus dosage received. Transmission is from person to person by the fecal-oral route. Hepatitis A virus is at the highest levels in feces 1 to 2 weeks before the symptoms occur  and  decreases  rapidly  after  the  onset  of jaundice. Many outbreaks are spread by food and water.  Raw  or  under-cooked  clams  and  oysters have  been  incriminated.  Viral  hepatitis  A  appears to  be  most  communicable  during  the  2  weeks before  the  symptoms  occur  and  is  probably  not transmitted after the first week of illness. There is  no  specific  treatment,  except  for  supportive measures. 11-11