WHAT IS IT ?

Typhoid fever is a bacterial infection that has become rare in industrialized countries, but that is still common in countries with poor hygiene where it is responsible for 600,000 cases each year.

SYMPTOMS

- Following a 7 to 14-day incubation period, typical signs, including diffuse abdominal pain, possibly high fever, anorexia, and very often diarrhea, progressively appear.

- Daytime drowsiness and nighttime insomnia are characteristic signs.

- Possible complications include gastrointestinal hemorrhage and perforation, heart failure, and encephalitis.

- Effective antibiotics are available, and the prognosis in patients under treatment is usually favorable.

Nevertheless, recovery may be followed by chronic carriage during several months. Moreover, the emergence of drug-resistant strains makes the treatment more complex.

EPIDEMIOLOGY AND VACCINATION

- The reservoir of the pathogen is strictly human.

- Transmission usually occurs through the fecal-oral route by ingestion of contaminated food or water.

- Prevention relies on good hygiene and vaccination.

- Several vaccines against typhoid fever are available.

WHAT IS IT?

Pertussis is a highly contagious infection of the lower respiratory tract caused by the bacterium Bordetella pertussis. Pertussis is a slowly progressing disease (several weeks) that is particularly severe among young infants.

 

SYMPTOMS

- Typical pertussis is characterized by a persistent cough (over three weeks) in most cases in the absence of fever. Paroxysmal cough is associated with the typical inspiratory whoop, apnea, cyanosis or post-tussive vomiting.

- The disease may be particularly severe and even fatal in infants.

- Adolescents and adults usually present atypical forms of the disease associated with a persistent cough.

 

EPIDEMIOLOGY AND VACCINATION

- Pertussis is a strictly human disease. It is easily transmitted by close contact, mainly through coughing.

- Since the 1920s, the incidence of pertussis has decreased by more than 90% in countries that have introduced vaccination (19-20). Unfortunately, the disease still raises concern due to the increase in the proportion of cases occurring in infants too young to be vaccinated and in adolescents and adults in whom the protection provided by the disease or vaccination during their childhood is waning. The latter group may serve as a reservoir for the transmission to young infants.

- Vaccination against pertussis is included in the routine vaccination of infants and children from 2 months to 6 years of age.

- The availability of acellular pertussis vaccines now allows the administration of boosters for adolescents and adults.

WHAT IS IT?

Diphtheria is a bacterial infection caused by Corynebacterium diphtheriae. Before the introduction of routine vaccination, the disease ranked among the leading causes of infant mortality.

 

SYMPTOMS

- Following a 1-to-5 day incubation period, typical diphtheria presents as pharyngitis with seudomembranes that can spread, obstruct the airways and eventually lead to death by asphyxia. Complications of diphtheria include potentially fatal heart and neurological disorders.

- Diphtheria-related mortality remains high, with rates ranging from 5 to 20% during recent outbreaks.

- Diphtheria must be treated as an emergency in order to reduce the risk of complications and death. Treatment relies mainly on the administration of diphtheria antitoxin by the intramuscular or intravenous route. Antibiotics are also used to contain bacterial growth, but they have no effect whatsoever on toxin-induced symptoms.

 

EPIDEMIOLOGY AND VACCINATION

- Humans are the only natural reservoir of Corynebacterium diphtheriae. Transmission occurs through respiratory droplets and close physical contact.

- Before vaccination against diphtheria became readily available in the 1980s, it was estimated that approximately 1 million cases occurred in the developing countries of Eastern Europe each year.

- Diphtheria is still present in many countries and epidemics have broken out during the last decade.

- Diphtheria vaccines are produced from diphtheria toxoid, a non-toxic form of the toxin.

WHAT IS IT?

Cholera is caused by a bacterium,vibrio cholerae, which produces a toxin that affects the intestines.

This bacterium has been at the origin of devastating epidemics worldwide throughout history.

 

SYMPTOMS

After an incubation period ranging from a few hours to 4 days, cholera is mainly characterized by acute watery diarrhea associated with vomiting.

- The severity of the disease is mainly correlated to the risk of severe dehydration, which can lead to death in a few hours.

- Treatment thus relies on a rehydration adapted to the patient?s condition.

 

EPIDEMIOLOGY AND VACCINATION

- Cholera is a strictly human disease that is transmitted from person to person through fecally contaminated food and water and thus affects mainly developing countries in Asia, South America, and Africa. It is estimated to cause 120,000 deaths annually.

- Hygiene and sanitation are the cornerstones in the fight against this disease.

- Vaccination against cholera is available but provides only limited protection.

WHAT IS IT?

Haemophilus influenzae type b infections are widespread throughout the world. Hib infections may develop under various forms but meningitis is the most frequent one. Hib infections occur in children under the age of 5 years, and mostly during the first year of life.

 

SYMPTOMS

- Following colonization of the pharynx, the bacterium may enter the bloodstream, and subsequently spread to reach various target organs resulting in different clinical forms of Hib disease:meningitis, pneumonia, epiglottitis, arthritis, cellulitis, osteomyelitis.

- Hib meningitis is often fatal (in 5 to 40% of cases depending on the country) and may lead to neurological sequelae such as deafness, motor deficit, or mental retardation.

- Medical management relies on intensive care and appropriate antibiotic therapy.

 

EPIDEMIOLOGY AND VACCINATION

- Hib infections are strictly human. Children infect each other through saliva droplets or by playing with contaminated toys.

- Worldwide, Hib infections account for 3 million cases of severe illness, and 400,000 to 700,000 deaths annually, with a peak of incidence among infants of age 4 to 18 months. (4)

- The Hib vaccine is usually administered along with the other vaccines included in the childhood vaccination schedule. This vaccine has led to a rapid decline in the number of cases in industrialized countries, but its use is unfortunately not widespread in developing countries.

WHAT IS IT?

Meningococci are a major cause of bacterial meningitis and septicemia. There are several meningococcal serogroups, but serogroups A, B, C, Y, and W135 account for 99% of cases of invasive infection.

 

SYMPTOMS

- Meningococcal meningitis usually occurs during infancy, adolescence and young adulthood and is characterized by an infectious syndrome (fever, severe headaches, vomiting) with meningismus (stiffness of the neck, lethargy, consciousness disorder, and even coma).

- Purpura fulminans (or fulminant meningococcal septicemia) is seen in 10 to 20% of patients (15). It is characterized by infectious shock and extensive, often ecchymotic, purpura. The mortality rate is high and the sequelae drastic.

 

EPIDEMIOLOGY AND VACCINATION

- Although invasive meningococcal infections mostly appear in the form of sporadic cases or minor epidemics, unpredictable and devastating epidemics do occur in certain geographical areas, such as the ?African meningitis belt.?

- Transmission of meningococci occurs via airborne respiratory droplets expelled by infected patients or healthy carriers.

- Several types of meningococcal vaccines are available.

WHAT IS IT?

Pneumococcal bacteria can cause various invasive (meningitis, bacteremic pneumonia and bacteremia) and non-invasive (pneumonia, otitis, sinusitis, and bronchitis) infections caused by any serotype of the bacterium Streptococcus pneumoniae.

 

SYMPTOMS

- Pneumococcal pneumonia is the most common form of bacterial pneumonia. Symptoms include high fever, chills, and a productive cough accompanied by pulmonary pain and breathing difficulties. Pneumococcal pneumonia is frequently associated with bacteremia (i.e., the presence of bacteria in the blood).

- The associated mortality is increased by the presence of pre-existing risk factors such as underlying disease, malnutrition or age.

- Symptoms of pneumococcal meningitis are undistinguishable from those of other bacterial meningitis and include fever, headaches, vomiting, and stiffness of the neck. The associated mortality is high, especially among infants and the elderly.

 

EPIDEMIOLOGY AND VACCINATION

- Pneumococci are transmitted by direct contact with respiratory secretions of infected patients or healthy carriers. Pneumococcal infections occur in all age groups, but their severity is highest in the very young and elderly.

- Pneumococcal infections are significant in both developing and industrialized countries.

- Several types of pneumococcal vaccine are available.

WHAT IS IT?

Tetanus is an often fatal infectious disease caused by the toxigenic strains of the tetanus bacillus. Tetanus is a devastating disease in developing countries and has not yet entirely disappeared from industrialized countries.

 

SYMPTOMS

- The bacterium penetrates the body through lesions (e.g., soiled wounds, open fractures, chronic ulcers?) or as a result of medical acts performed under insufficient aseptic precautions.

- Following an incubation period of 4 to 21 days, tetanus most often presents as a generalized spastic disease. Contractions of the jaw muscle (or trismus) are a characteristic feature and are followed by spasms of the back muscles (opisthotonos) and sudden generalized convulsions.

- In the absence of treatment, the outcome is almost always fatal, particularly in the very young or the elderly.

- Even after appropriate treatment, tetanus-related mortality remains high.

 

EPIDEMIOLOGY AND VACCINATION

- Tetanus bacillus is ubiquitous and present in the soil in the form of highly resistant spores. Its reservoir can thus not be eliminated, but vaccination is a very effective weapon in the prevention of the disease.

- In 2002, over 200,000 tetanus-related deaths were estimated to occur worldwide, of which approximately 180,000 were due to neonatal tetanus. (26)

- Tetanus vaccines are based on tetanus toxoid, and are usually combined with other valences (e.g., diphtheria, pertussis, polio, Hib?).

WHAT IS IT?

Tuberculosis is a contagious bacterial disease caused by the bacillus Mycobacterium tuberculosis. With 8 million new cases each year, tuberculosis is the second leading cause of death from infectious diseases throughout the world, after acquired immune deficiency syndrome (AIDS).

 

SYMPTOMS

- Following infection, usually through the airborne route, the bacteria grow within the pulmonary alveoli and macrophages. When bacterial multiplication can no longer be contained by the immune system (in 5 to 10% of patients), the active disease develops.

- The most common form of active tuberculosis is the pulmonary form. Symptoms include chronic cough, moderate fever, nighttime sweats, fatigue, decreased appetite and weight loss.

- Miliary (diffuse impairment of lungs, spleen, liver, and bone marrow) and meningeal tuberculosis are the most severe forms of the disease.

- Treatment relies on the administration of anti-tuberculosis drugs for many months.

 

EPIDEMIOLOGY AND VACCINATION

- Approximately one third of the people on the planet are infected by the bacillus but the infection remains latent. Among them, only 5 to 10% will go on to develop an active form of the disease.

- A tuberculosis vaccine is administered in many countries by the intradermal route, at birth, during infancy or before school entry.

- The tuberculosis vaccine does not prevent reactivation of the latent forms and has no impact on the transmission of the disease, but it is of great value in the prevention of the most severe forms of the disease (e.g., childhood meningeal tuberculosis).