Diseases

Influenza and Contagious Respiratory Illnesses

Last Updated: June 10, 2025
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​​Several respiratory illnesses have symptoms such as runny or stuffy nose and coughing that may at first seem like the common cold but are more serious and even fatal in certain persons. These diseases are all contagious (can be passed from one person to another) through the air (usually from tiny droplets in the air when a sick person coughs, sneezes, or talks). People may also become infected when touching objects contaminated with the viruses or bacteria and then touching their eyes, nose, or mouth.

Key illnesses identified in the military population include these infections:

  • Viral: influenza (flu), COVID-19, respiratory syncytial virus (RSV), and measles
  • Bacterial: whooping cough (pertussis)

While risks among service members are lowered because of vaccine requirements, there is a potential for outbreaks on ships and in other close-quartered environments. Also, family members may be at increased risk, especially those who are less-than-fully-​vaccinated because of young age, medical conditions, or other reasons.

While both the Centers for Disease Control and Prevention (CDC) and military public health tracking data show these acute respiratory diseases occur throughout the year, they are more common in fall and winter. It is possible to experience more than one of these diseases at the same time.

Children are often exposed to and infected these diseases outside the home such as in school or childcare centers, they can then transmit the virus to other members of the family. Some disease organisms can survive for many hours on hard surfaces such as tables and crib rails; it typically lives on soft surfaces such as tissues and hands for shorter amounts of time. These diseases tend to be more dangerous to children and infants and those over 65 years, or those with weakened immune systems.​ 

Prev​​ention

While there are some differences in symptoms and treatment, prevention measures are similar for all these repiratory illnesses.

Do your part to protect yourself and reduce the spread of these diseases:

The first and most critical prevention measure is to get vaccinated for each disease.  For some diseases, vaccines will prevent the disease from occurring altogether. In some cases, such as with the flu, the vaccine may not always prevent the illness completely but can reduce the severity of symptoms or length of illness and prevent risk of related complications including death.

Other actions include:

  • Avoid close contact with people who are sick.
  • If you are sick, stay home and limit contact with others.
  • Avoid touching your eyes, nose, and mouth.
  • Clean hands often with soap and warm water or alcohol-based hand cleaners.
  • Use a tissue to cover your mouth and nose when you sneeze or cough. Throw the tissue in the trash after you use it. If a tissue is not available, then sneeze or cough into the inside of your elbow, not your hand.​

Specific diseases are discussed below.  

Influenza (Flu)

Military occurrence and impact of the flu is moderate (seasonal). Flu vaccinations reduce impacts, but illness can result in lost duty time. Cases that result in hospitalizations are required to be reported. 

  • Cause/Exposure: A contagious (human to human, airborne) illness caused by influenza viruses. Flu season in the U.S. usually occurs during the winter months, however cases can occur throughout the year. 
  • ​Symptoms: Common symptoms, listed below, usually come on suddenly. Most people who get the flu will recover in a few days to less than two weeks.
    • Fever (not everyone with flu will have a fever)
    • Headache
    • Fatigue (tiredness)
    • Cough
    • Sore throat
    • Runny or stuffy nose
    • Muscle or body aches
    • Some people may experience vomiting and diarrhea, but this is more common in children than adults.
  • Vaccine (annual): The best way to prevent flu is by getting a flu vaccine each year along with preventive actions like handwashing and covering coughs and sneezes. The flu vaccine is updated each year based on changes to the virus – an annual vaccine is needed. Flu vaccines help to reduce the military medical burden of flu illnesses, doctors' visits, hospitalizations, and deaths each year. Military facilities can encourage vaccination with this DHA Flu Vaccine Poster
  • Treatment: As a viral infection, antibiotics are not an effective form of treatment. However, antibiotics may be useful in treating secondary bacterial infections that can result from or occur with the flu. Most treatment for flu is symptomatic though doctors may prescribe an antiviral if caught early. 
  • Additional influenza information sources: 
  • Military cases and clinician/provider guidance:

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COVID-19

  • Cause/Exposure: A contagious (human to human, airborne) illness caused by a virus, COVID-19 commonly occur at times or locations that large groups of people are in close contact, such as outdoor event (summer) and holidays (winter) but cases can occur throughout the year.
  • ​Additional COVID information sources: 


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Measles

Military occurrence and impact of the measles is rare but a recent decline in measles vaccination rates worldwide have led to the increased risk of measles cases in the U.S.

While measles in service members is rare because of vaccine requirements, there is a potential for outbreaks on ships and in other close-quartered environments. Family members may be at increased risk, especially those who are less-than-fully-vaccinated because of young age, medical conditions, or other reasons.



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Respiratory Syncytial Virus (RSV) Infection

Respiratory Syncytial Virus (RSV)External Link is a common respiratory virus that causes mild, cold-like symptoms. Most people recover from RSV in 1 to 2 weeks but it can be especially dangerous for infants and young childrenExternal Link​and adults over 65,External Link​ especially those​ with certain high risk medical conditions such as chronic lung or heart conditions, weakened immune systems, or neuromuscular disorders.

  • Cause/Exposure: People are typically infected with RSV for the first time as an infant or toddler, and nearly all children are infected before their 2nd birthday.External Link However, repeat infections may occur throughout life, and people of any age can be infected. People infected with RSV are assumed contagious for 3 to 8 days including 1 to 2 days before they start showing signs of illness. However, some infants, and people with weakened immune systems, can still spread the virus even after they stop showing symptoms, up to 4 weeks. ​
  • Symptoms: Symptoms of RSV infection usually include runny nose, decrease in appetite, coughing, sneezing, fever, and wheezing. In very young infants with RSV, the only symptoms may be irritability, decreased activity, and breathing difficulties. These symptoms usually appear in stages and not all at once. People infected with RSV usually show symptomsExternal Link within 4 to 6 days after getting infected. Infections in healthy children and adults are generally less severe than among infants and older adults with certain medical conditions. However, some severe effects such as pneumonia can occur in older and high-risk adults. 
  • Vacci​​nesExternal Link​: High risk persons should consider RSV vaccines (talk to your provider)
  • Treatment: As a viral infection, antibiotics are not an effective form of treatment. However, antibiotics may be useful in treating secondary bacterial infections.

 

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​Whooping Cough (Pertussis)

Whooping cough, also known as pertussis, is a highly contagious respiratory illness caused by a type of bacteria called Bordetella pertussis. Babies younger than 1 year old are at greatest risk for getting whooping cough, developing severe complications, and needing hospitalization. See Whooping Cough Poster. 

  • Cause/Exposure: The bacteria that cause whooping cough spread easily from person to person through the air when a person with whooping cough coughs or sneezes. 
  • Symptoms: Early symptoms of whooping cough can look like a common cold. Early symptoms can appear 5 to 10 days after exposure to the bacteria that cause whooping cough and can last for 1 to 2 weeks. Symptoms can include: 
    • ​Runny or stuffy nose
    • Low-grade fever (less than 100.4℉) 
    • Mild, occasional cough 
    • Though many infants with whooping cough do not cough or may have short bursts of coughing others may experience apnea, which is a pause in breathing. 
    • Later symptoms usually appear 1 to 2 weeks after the first symptoms start. Rapid, violent, and uncontrolled coughing fits called paroxysms are the most notable symptom of whooping cough. Coughing fits usually last 1 to 6 weeks but can last up to 10 weeks and can cause people to: 
      • Make a “whoop” sound as they inhale after a coughing fit 
      • Vomit during or after coughing fits 
      • Feel exhausted​ 
  • ​Vaccine: The best way to prevent whooping cough is to get vaccinated. There are two types of vaccines that include protection against whooping cough, DTaP and Tdap. Together, these vaccines provide protection against pertussis, diphtheria, and tetanus. Infants and children younger than 7 years old receive the DTaP vaccine, while older children and adults receive the Tdap vaccine. Vaccine protection for pertussis, tetanus, and diphtheria fades over time, but adults can protect themselves and the children they are in close contact with by getting a booster vaccine.
  • ​Treatment: It is important to treat whooping cough early, before coughing fits begin. Since this is a bacterial infection, whooping cough is typically treated with antibiotics. Most symptoms can be managed at home but treatment in a hospital may be necessary if symptoms become serious. Early diagnosis and treatment of whooping cough may make the infection and symptoms less severe and help reduce the spread of whooping cough. 
  • Additional whooping cough resources:

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Additional Resources