Epidemiology, Prevention Communicable Diseases

Article Author:
Peter Edemekong
Article Editor:
Ben Huang
Updated:
10/27/2018 12:31:33 PM
PubMed Link:
Epidemiology, Prevention Communicable Diseases

Introduction

Communicable diseases are illnesses caused by viruses or bacteria that people spread to one another through contact with contaminated surfaces, bodily fluids, blood products, insect bites, or through the air. There are many examples of communicable diseases, some of which require reporting to appropriate health departments or government agencies in the locality of the outbreak. Some examples of the communicable disease include HIV, hepatitis A, B and C, measles, salmonella, measles and blood-borne illnesses. Most common forms of spread include fecal-oral, food, sexual intercourse, insect bites, contact with contaminated fomites, droplets, or skin contact.

Specifically, hepatitis is a form of a communicable disease that is spread through the oral-fecal route. An individual is exposed to hepatitis by coming in contact with blood products, consuming contaminated water, having sex with another infected person (oral and intercourse), or eating food that is contaminated by the virus. There are six criteria that need to be met to diagnose a hepatitis infection. These criteria include an infection agent, in this case, the hepatitis virus, a reservoir, route of infection, transmission mode, route of entry, and a susceptible subject who becomes infected with the virus.

Hepatitis A virus (HAV) is a communicable disease that is preventable through vaccination. It affects the liver causing jaundice. It is transmitted person-to-person through consumption of food, oral sexual contact, poor hand hygiene after using the bathroom or changing diapers, and water that is contaminated. It is one of the most reported outbreaks in the United States. It is self-limited after ingestion through contaminated food sources. The virus replicates in the liver, is excreted in bile, and can reach high concentrations in the stool.

Stool concentrations are highest 2 weeks after transmission. Patients are considered non-infectious about a week after inoculation or the onset of jaundice. Patients who are symptomatic most often present with acute onset fever, malaise, jaundice, hepatomegaly, and abdominal pain. Jaundice is often followed with marked elevated of serum aminotransferases that is greater than 1000 units/L. The test of choice is IgM anti-hepatitis A virus for diagnostic purposes. There is no specific therapy available. Presently, supportive and conservative management is the mainstay of treatments. Prevention includes personal hygiene or with active or passive immunization.

Function

There are four major patterns of HAV infections worldwide divided into areas of high, intermediate, low, or very low prevalence. Endemic areas of high prevalence include parts of Africa, Asia, and Latin America. Most infections in these areas occur in early childhood. Areas of low prevalence and very low prevalence include North America and Western Europe with few infections during childhood and majority of the population are susceptible throughout adulthood.

In the United States, HAV is one of the most reported diseases among vaccine-preventable diseases. Over 30,000 cases were reported in 1997. An estimated 270,000 HAV infections are said to have occurred each year between 1980 and 1999. A total of 1390 cases of hepatitis A were reported from 50 states to the Centers for Disease Control and Prevention (CDC) in 2015. There was a 12.2% increase from reported cases of HAV in 2014. Of note, the overall incidence in 2015 was 0.4 cases per 100,000 population which was the same as in 2014 (CDC, 2017). Since 1996, the declining incidence in the United States is attributed to the widespread use of HAV vaccination for populations considered high-risk. An incidence of 1 case per 10,000 was notably the lowest recorded in 2007. States with routine vaccination for children also noticeably made the most noticeable difference (Epocrartes, 2017). Overall, there has been a 95% decline in HAV in the United States since the vaccine for HAV became available in 1995.

Globally, the epidemiology of HAV is evolving, in part attributed to improved sanitation standards and living conditions mostly noticeable in developing countries. This has undoubtedly contributed to the global decline in the number of infected children globally. However, the incidence among adults has increased due to the larger population of an adult who lacks antibodies that are protective against HAV.

Issues of Concern

Recently, the Division of Disease Control and Health Protection issued a Healthcare Provider Advisory note on HAV in the State of Florida indicating that 217 cases have been in reported in the State of Florida alone since January 2017, a significant increase when compared to the past 5-year average of 94 cases. Of note was the fact that most HAV cases did not have international travel exposure. Southeast Florida (e.g., Broward and Miami-Dade counties) had the most cases of HAV with 69% among males (most had male sexual contact). The median age of reported cases was 38 years with highest rates of Hepatitis A disease recorded among people ages 25 to 44 years. About 60% of the cases of HAV in Florida required hospitalization.

Also of note is the fact that nearly 1200 outbreaks of HAV were recorded among individuals who are homeless, use intravenous (IV) drugs, men who have sex with men, and their close or direct contacts as investigated by the health departments in Arizona, California, Colorado, Michigan, New York and Utah (DOH, Florida 2017).

Clinical Significance

History and Physical Examination

  • Acute onset fever
  • Fatigue
  • Malaise
  • Nausea and vomiting
  • Jaundice
  • Hepatomegaly
  • Right upper quadrant pain
  • Joint pain
  • Clay-colored bowel movements

Other Clinical Factors

  • Headache
  • Fatigue
  • Dark urine
  • Pruritus
  • Rash
  • Arthralgias and myalgias
  • Cough
  • Bradycardia
  • Diarrhea
  • Constipation
  • Splenomegaly
  • Posterior cervical lymphadenopathy

Diagnostic Tests

  • Serum aminotransferases
  • Serum bilirubin
  • BUN
  • Serum Creatinine
  • Prothrombin time
  • IgM anti-hepatitis A virus (HAV)
  • IgG anti-hepatitis A virus (HAV)
  • Stool and body fluid electron microscopy
  • Hepatitis A virus RNA

Treatment Options

Presumptive: If unvaccinated with recent exposure to HAV less than 2 weeks: HAV or immune globulin

Acute presentation HAV infection

  • Confirmed HAV: Supportive and conservative management
  • Worsening jaundice and encephalopathy: liver transplant

Recommendations of the Advisory Committee on Immunization Practices: DOH Florida, 2017.

  • All children at age 1 year
  • Persons who are at increased risk for infection
  • Persons who are at increased risk for complications from HAV
  • Any person wishing to obtain immunity

Other Issues

Recommendation for two-dose HAV vaccine, 6 to 12 months apart for the following persons:

  • Men who have sex with men
  • Injection and non-injection drugs users
  • Persons with chronic liver disease
  • Persons traveling to or working in countries with high or intermediate endemicity of hepatitis A
  • Persons with clotting-factor disorders
  • Household members and other close personal contacts of adopted children newly arriving from countries with high or intermediate hepatitis A endemicity
  • Persons with direct contact with persons who have hepatitis A