138 Workplace Hygiene and Illness Prevention

Communicable Diseases

In the workplace, communicable infectious diseases are most commonly spread through respiratory droplets and airborne particles containing pathogens, such as viruses and bacteria, that are released when an infected person breathes, talks, coughs, or sneezes. Examples of communicable infectious diseases include:

• Influenza (flu): A contagious respiratory illness caused by influenza viruses. It affects the nose, throat, and sometimes the lungs. The World Health Organization (WHO) estimates about 1 billion seasonal influenza infections each year, including 3–5 million severe cases.
• Coronavirus Disease 2019 (COVID-19): A contagious respiratory illness caused by the SARS-CoV-2 virus. Although the global public health emergency has ended, COVID-19 continues to circulate and can cause mild to severe illness, including long COVID in some people. It spreads mainly through virus-containing droplets and tiny airborne particles released when an infected person breathes, talks, coughs, or sneezes. People can spread the virus even if they have no symptoms. Surface transmission is possible but is not considered a common route of infection.
• Norovirus: The norovirus, also known as the stomach flu, is a highly contagious virus that causes acute gastroenteritis (inflammation of the stomach and intestines). It is the leading cause of foodborne illness worldwide and is responsible for an estimated 685 million cases of acute gastroenteritis each year, including approximately 200 million cases in children under age 5. Norovirus spreads easily through contaminated food or water, direct contact with an infected person, or by touching contaminated surfaces and then touching the mouth.
• Measles: A highly contagious, serious disease that is spread through the coughing and sneezing of individuals infected by the measles virus. Prior to vaccinations in 1963, 3-4 million infections were reported each year, but the statistics were under-reported. Prior to vaccinations, nearly every child in the U.S. contracted measles before age 15. Those who had contracted measles also achieved permanent immunity from the disease. In the decades prior to the vaccinations, mortality had already fallen substantially due to better nutrition, supportive care, and antibiotics for secondary infections, but case numbers and non-fatal complications remained high until vaccination.
• Strep Throat: A contagious bacterial infection caused by Group A Streptococcus (Streptococcus pyogenes) that affects the throat and tonsils. It is estimated that tens to hundreds of millions of cases occur worldwide each year, with the highest rates among school-aged children (5–15 years old). Strep throat spreads through respiratory droplets released when an infected person coughs, sneezes, or talks, and through direct contact with contaminated hands or objects.
• Food Poisoning (Gastroenteritis): Food poisoning symptoms include severe stomach cramps, diarrhea (which may become bloody), nausea, vomiting, and sometimes a low-grade fever. It is caused by Escherichia coli (E. coli) bacteria found in the environment, food, and intestines of people and animals. It causes millions of foodborne illnesses worldwide each year, but far fewer than respiratory viruses. Most strains of E. coli are harmless, but others can make you sick.
• Mumps: Mumps is caused by a virus (a paramyxovirus) and spreads primarily through respiratory droplets (coughing, sneezing, talking) or direct contact with an infected person’s saliva. It can also spread through shared items contaminated with saliva. Before widespread vaccination, mumps was a common childhood illness that caused epidemics. Complications can include orchitis (testicular inflammation), meningitis, encephalitis, hearing loss, and (rarely) more serious outcomes, though most cases are mild or moderate.

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