Infectious and Communicable Diseases

Etiology of Infectious and Communicable Diseases

• Infectious diseases are caused by microorganisms that can be transferred to new individuals.
• Communicable diseases are easily transmitted from one person to another.
• Reservoir species involved in disease transmission include wild vertebrate animals.
• Intermediate/amplifier species in disease transmission include domesticated vertebrate animals.
• Vector species involved in disease transmission are biting arthropod animals.

Transmission and Incubation Periods for Selected Diseases

• AIDS is transmitted through intimate sexual contact, semen, blood, blood products, contaminated needles, placental transmission, and breast milk; antibodies appear within 1-3 months of infection
• Anthrax is transmitted through breaks in the skin, inhalation, or consumption of contaminated meat; incubation is 1-43 days, varying with exposure strength.
• Botulism is transmitted by eating contaminated food; incubation is 6-10 hours after exposure.
• Common cold (coryza) is transmitted through airborne respiratory droplets, hand-to-hand contact, and contaminated items; incubation is 2-5 days.
• COVID-19 is transmitted through airborne respiratory droplets; contact with contaminated items; incubation is 2-14 days.
• Diphtheria is transmitted through intimate contact with discharges from the nose, throat, eye, and skin lesions; incubation is 2-5 days.
• E. coli O157:H7 is transmitted by eating/drinking contaminated food/water, or swimming in sewage-contaminated water; incubation is 1-8 days.
• Erythema infectiosum (fifth disease) is transmitted through respiratory secretions or direct contact; incubation is generally 4-14 days.
• H1N1 influenza is transmitted through respiratory secretions or hand-to-hand contact; incubation is 1-7 days.
• Infectious diarrheal diseases are transmitted via the oral-fecal route; incubation is 48 hours.
• Influenza is transmitted through respiratory secretions, hand-to-hand contact, and contaminated items; incubation is 1-3 days.
• Methicillin-resistant Staphylococcus aureus (MRSA) is transmitted through close contact with infected persons or indirect contact with towels, wound dressings, or sports equipment; incubation is unpredictable, usually 1-10 days after the MRSA enters the bloodstream.
• Mumps is transmitted by droplets of saliva or airborne; incubation is 18 days.
• Pertussis (whooping cough) is transmitted by droplets of respiratory secretions or contact with contaminated items; incubation is 7-10 days.
• Plague (pneumonic) is transmitted by close contact with infected individuals or respiratory droplets; incubation is 1-6 days.
• Rubeola (hard measles) is transmitted by respiratory droplets from the nose and throat; incubation is 8-13 days, with a rash appearing around 14 days.
• Rubella (3-day measles) is transmitted by respiratory droplets from the nose and throat; incubation ranges from 14-23 days, commonly 16-18 days.
• Smallpox is transmitted by respiratory droplets or infected dried scales from lesions, contact with contaminated items; incubation is 10-14 days after exposure.
• Varicella (chickenpox) is transmitted by respiratory secretions and direct contact; incubation is usually between 13 and 17 days.
• Viral hemorrhagic fevers are transmitted through airborne transmission or contact with infected hosts (animals, flies, mosquitoes); incubation is 2-21 days.

Emerging and Reemerging Infections

• A list of emerging and reemerging infections is created by the National Institute of Allergy and Infectious Diseases (NIAID).
• The NIAID list changes regularly.
• Some emerging and reemerging infections could be weaponized.

Pandemics

• Pandemics are epidemics that have crossed international boundaries, affecting people worldwide.
• Antimicrobial resistance is increasing among nosocomial infections that cause sepsis or bacteremia.
• The CDC encourages providers not to prescribe antibiotics for viral illnesses.
• Overuse of antibiotics can cause them to lose their effectiveness.
• The CDC website lists common organisms that develop resistance to antibiotics.
• COVID-19 is caused by SARS-CoV-2, possibly originating from bats.
• H1N1 (swine flu) is a mix of pig, bird, and human viruses.
• Escherichia coli are bacteria in the intestinal tract of humans and animals.
• Lyme disease is caused by a tick-borne spirochete.
• Severe Acute Respiratory Syndrome (SARS) is caused by the coronavirus SARS-CoV.
• Middle East Respiratory Syndrome (MERS) is caused by the coronavirus MERS-CoV.
• MERS is a recent emerging infection with a 30% death rate.
• MERS was first seen in Saudi Arabia.
• MERS can transfer from person to person and may have come from camels or bats.

Infectious Diseases as Potential Weapons

• Anthrax is an acute bacterial infection that occurs in cutaneous, intestinal, or inhalation forms.
• Botulism is a bacteria that causes muscle paralysis.
• Plague (pneumonic) is a bacteria that spreads through respiratory secretions.
• Smallpox (variola) is a variola pox virus that spreads through respiratory secretion.
• Tularemia (rabbit or deer-fly fever) is a bacteria that causes pneumonia-like infection.
• Viral hemorrhagic fevers are highly infectious viruses that damage multiple organ systems.

Mosquito Borne Diseases

• West Nile Virus is transmitted by the bite of an infected mosquito.
• Malaria is caused by protozoa from an infected mosquito.
• Malaria parasites travel to the liver, changing into merozoites that enter and destroy red blood cells.

Viral Infections and MRSA

• Viral infections include the common cold (coryza) and influenza.
• The common cold is a virus of the upper respiratory tract.
• Influenza is an acute viral infection of the respiratory system.
• Multidrug-resistant organisms include Methicillin-resistant Staphylococcus aureus (MRSA).

Immunosuppressant Diseases

• Chronic fatigue syndrome is characterized by persistent, debilitating fatigue and is difficult to treat.
• HIV infection/AIDS is a viral infection that destroys T4 lymphocytes, and has no cure, but antiviral medications can suppress the virus.

Infectious and Communicable Diseases of Childhood and Adolescence

• Infectious diarrheal disease is transmitted through the fecal-oral route, affecting 20 million cases a year.
• Rubeola (measles) is a highly communicable respiratory infection preventable by vaccine.
• Rubella (3-day measles) is caused by the rubella virus and characterized by fever and rash; dangerous to pregnant women.
• Mumps is characterized by inflammation of the parotid salivary glands caused by mumps paramyxovirus; preventable by vaccine.
• Varicella (chickenpox) is caused by the varicella-zoster virus, causing a rash that goes from macule to papule to vesicles, then crusts; prevented by vaccine; reappears as shingles in later life.
• Erythema infectiosum (Fifth disease) is caused by human parvovirus B19, transmitted by respiratory secretions, and is characterized by facial rash.
• Pertussis (whooping cough) is a bacteria that causes a highly infectious respiratory disease with a repetitive, paroxysmal cough and prolonged harsh or shrill sound during inhalation; preventible by vaccine.
• Diphtheria creates a membrane-like coating over mucous membrane surfaces, which can block airways; preventable by vaccine.
• Tetanus (Lockjaw) is a life-threatening disease causing skeletal muscle contractions; comes from the environment (Clostridium tetani); preventable by vaccine.

Immunizations

• Immunizations provide protection against certain communicable diseases.
• Vaccines are suspensions of infectious agents, components of the agents, or genetically engineered antigens to establish resistance to an infectious disease.
  • The two general classes of vaccines are live attenuated agents and inactivated agents obtained through genetic mutation.

COVID-19

• Only confirmed cases can be coded.
• Suspected or inconclusive cases should not be used.
• Manifestations of COVID-19 include other respiratory syndromes coded according to their description.