Respiratory Illnesses

Avian Influenza

Avian influenza ("bird flu") is a serious viral infection that occurs mainly in poultry, waterfowl, and migratory birds. Human infection is rare but does occur. Most human cases result from direct contact with infected poultry or their droppings. Exposure can also occur via respiratory secretions or eye secretions of infected birds or through contact with contaminated surfaces. Humans can be exposed by eating undercooked, infected poultry or eggs or duck blood or by inhaling dried, airborne poultry feces. Initial symptoms resemble a severe case of regular influenza: fever, chills, cough, runny nose, sore throat, muscle aches, and headaches; however, the person then deteriorates rapidly, suddenly developing severe pneumonia and respiratory distress about 3 to 5 days into the illness.

Prevention: If traveling in an area where avian influenza is occurring in poultry or humans (mainly in Southeast Asia and China), follow preventive measures. Observe respiratory hygiene (cough and sneeze etiquette) and hand hygiene (frequent, thorough handwashing); carry and use alcohol-based hand sanitizers or towelettes. Avoid all contact with birds and poultry, any surface that may be contaminated, live animal markets ("wet markets"), and poultry farms. Avoid consumption of poultry in affected areas because it is difficult to determine visually whether the meat is fully cooked. Get vaccinated against regular influenza before leaving; it will not protect against avian influenza but may decrease the chance of confusing seasonal influenza with avian influenza if illness occurs.


Coronavirus disease 2019 (COVID-19)−an acute viral respiratory infection that originated in China in late 2019−is responsible for a global pandemic causing hundreds of millions of cases and millions of deaths. Risk should be assumed present in all countries of the world and is higher with contact exposure and inpatient or outpatient visits to health care facilities in an affected area. Transmission occurs from exposure to infectious respiratory fluids (droplets and particles) from an infected person via inhalation, direct deposition of particles on mucous membranes by splashes and sprays, and contact (touching mucous membranes with contaminated hands). Risk of transmission is greatest within 1 to 2 m (3-6 ft) of an infectious source, where the concentration of these very fine droplets and particles is greatest. Symptoms commonly include fever and dry cough, progressing to shortness of breath; chills, muscle pain, headache, sore throat, congestion, and runny nose may occur. Loss of smell and/or taste is an early and highly specific symptom. Some infected persons have no symptoms. Consequences of infection include severe pneumonia, respiratory failure, liver and heart damage, prolonged fatigue, altered mental status, memory loss, and possibly death. Risk of poor outcome increases with age and is higher in persons (regardless of age) with underlying medical conditions (e.g., cancer, obesity, pregnancy, diabetes, sickle cell disease, solid-organ transplantation, or cardiac or kidney disease). A variety of variants of the original virus have been identified and mutations will continue to occur, which will affect the severity and transmissibility of the virus and the potential effectiveness of vaccines. Two types of COVID-19 tests are available, a viral (PCR or antigen) test for current acute infection using respiratory samples (e.g., swabs of the nose, mouth, or throat or saliva) and an antibody (serology) test for a previous infection using blood samples (e.g., finger stick or blood draw). The detection of antibodies does not necessarily indicate protective immunity and should not be used to detect acute infection when viral tests were negative or were not performed early after symptom onset.

Prevention: Vaccination with an authorized COVID-19 vaccine is recommended for all eligible travelers; all travel (domestic and international) during the pandemic should be postponed until fully vaccinated. Observe social distancing, respiratory hygiene, and hand hygiene and wear a mask; community wearing of an appropriate mask (ideally either a tightly fitting surgical mask or 2 separate masks) substantially reduces transmission. Unvaccinated travelers and vaccinated travelers with significantly weakened immune systems should always mask.


Diphtheria is an acute bacterial disease transmitted through respiratory droplets and contact with skin lesions. Symptoms include sore throat, hoarseness, nasal drainage, fever, difficulty swallowing, and a thick, gray membrane covering the back of the throat. It can be fatal. Diphtheria occurs worldwide, but mostly in developing countries.

Prevention: Vaccination with a primary series of diphtheria, tetanus, and pertussis vaccine is recommended. See Tetanus for booster doses.


Classic (seasonal) influenza is an acute highly contagious, viral respiratory illness transmitted via inhalation of aerosolized respiratory droplets or direct contact with contaminated surfaces. Influenza is the most common vaccine-preventable disease among travelers, including passengers on cruise ships. Influenza affects the entire body, causing significant illness and possibly death. Symptoms start suddenly, usually with a high fever, chills, severe body aches, extreme tiredness, headache, and a dry cough.

Prevention: Annual vaccination with influenza vaccine is recommended for all travelers 6 months and older. Because of year-round circulation of influenza virus in tropical and subtropical regions and an influenza season that occurs in winter in temperate regions in the southern hemisphere (which is summer in the northern hemisphere), all travelers going to the tropics at any time of year and to temperate destinations where it is currently winter should receive the most current influenza vaccine available in their home country before traveling. Travelers should observe respiratory hygiene and hand hygiene at all times because influenza vaccine is generally only about 60% effective. Travelers who cannot get vaccinated due to imminent departure or unavailability of vaccine at the time of year of travel should speak to their health care provider about a prescription for oseltamivir to carry for self-treatment.

Legionella Infection

Legionella infection or Legionnaires' disease is a bacterial pneumonia caused by Legionella pneumophilia, which is spread through the inhalation of infected aerosolized water from a variety of sources, such as air-conditioning and cooling systems, water-cooling towers, and whirlpool baths. Symptoms include high fever, chills, headache, respiratory symptoms, chest pain, and muscle aches.

Prevention: Avoid whirlpool-type spas and be aware of risk factors (e.g., male, age 40-70 years, smoker, chronic illness).

Meningococcal Disease

Meningococcal disease is a potentially fatal infection caused by the Neisseria meningitidis bacteria, which enter the body through the upper respiratory tract. Most people who become infected develop very mild upper respiratory symptoms or no symptoms at all. Severe cases can lead to meningitis (infection of the membranes covering the spinal cord and brain); symptoms of meningitis include severe headache, stiff neck, high fever, nausea and vomiting, and sensitivity to light. If the disease progresses, it can lead to convulsions, coma, and death. Meningitis can progress rapidly, so prompt treatment with antibiotics is extremely important. Risk to travelers is generally low but increases as length of stay increases and level of contact with the local population increases. Meningococcal infections occur most commonly in poor, overcrowded areas. Epidemics occur each year in the "meningitis belt" of Africa (especially during the December through June dry season).

Prevention: Vaccine is available to protect against meningococcal disease and is routinely recommended for some persons in developed countries and for others traveling to certain developing countries, notably in the meningitis belt of sub-Saharan Africa. Persons participating in an annual pilgrimage to Mecca (Hajj or Umra) are required to produce a certificate of vaccination against meningococcal meningitis issued not more than 5 years and not less than 10 days before arrival in Saudi Arabia. Observe respiratory and hand hygiene, especially when traveling to developing countries.

Middle East Respiratory Syndrome Coronavirus

Middle East respiratory syndrome coronavirus (MERS-CoV) is an acute viral respiratory infection that has caused more than 2,500 cases and many deaths (mainly in the Arabian Peninsula) since April 2012. Camels are likely the source of MERS-CoV; however, camel-to-human transmission is rare. Most cases have been transmitted from human to human in hospitals with poor infection-control procedures. Pneumonia in young healthy individuals is generally mild.

Prevention: Observe respiratory and hand hygiene; avoid all wild and farm animals, especially camels; and social distance (> 1 m [> 3ft]) from ill-appearing persons in affected areas of the Middle East. Travelers should avoid hospitals that may have substandard infection-control standards. If respiratory symptoms arise after travel to an area where cases have been reported, seek medical care.


Pertussis (whooping cough) is a highly contagious bacterial disease that is spread through inhalation of bacteria from an infected person and is most common in countries where vaccination is not generally provided. Pertussis is characterized by mild upper respiratory symptoms resulting in coughing spells so extreme that it is hard to eat, drink, or breathe, followed by a high-pitched "whoop" when breathing in. Pertussis can lead to pneumonia, seizures, brain damage, and death.

Prevention: The best prevention is childhood vaccination, which is usually given in combination with diphtheria and tetanus vaccines to children younger than 7 years. A Tdap booster is recommended for all travelers every 10 years (assuming receipt of an adequate primary series) because of increasingly frequent pertussis outbreaks worldwide. Those who received a tetanus booster that didn't contain a pertussis component for their most recent booster should receive a dose of Tdap immediately, regardless of the interval since the last tetanus dose. (See Tetanus.)


Tuberculosis (TB) is an infectious disease caused by bacteria (Mycobacterium tuberculosis). TB most commonly affects the lungs, but any organ of the body can be affected. TB is usually spread when infected people cough and droplets are inhaled by those nearby. Persistent cough, fever, night sweats, weight loss, fatigue, chest pain, and bloody sputum are symptoms of infection, but they are not always present. TB is a risk for travelers going to areas where TB is endemic, especially for persons who will be in the area for longer than 1 month, health care providers, and persons working in aid situations. Drug-resistant TB, which is becoming more prevalent in almost all countries, makes treatment more difficult.

Prevention: Avoid close physical contact with persons who are coughing or otherwise obviously ill. Long-stay travelers should screen domestic help for TB. A vaccine called Bacille Calmette-Guérin (BCG) is used in many developing countries and is also recommended in some industrialized countries for long-stay traveling children under the age of 5 years going to highly endemic areas. BCG is ineffective in adults. Pre- and posttravel TB screenings with a skin test or blood test are recommended for long-stay travelers going to moderate- or high-risk areas.