WHAT IS IT ?

Hepatitis A is a virus that causes an acute inflammation of the liver and is the most common form of all viral hepatitis. Hepatitis A is encountered frequently in the most disadvantaged geographical regions.
Improvements in hygiene and sanitation have led to a reduction in the circulation of the virus, but not to its complete disappearance.

SYMPTOMS

- Hepatitis A is often asymptomatic in young children, and more severe in adults. After an incubation period of 15 to 45 days, the onset of the disease is marked by a sensation of generalized malaise including, fever, headache, muscle soreness, fatigue, and gastrointestinal disorders.It is often accompanied by jaundice, particularly in adults.
- The condition may be long-lasting, with an acute phase of approximately one month and a convalescence phase of up to 6 months. - No specific treatment is available.

EPIDEMIOLOGY AND VACCINATION

- Hepatitis A is a strictly human disease. Transmission occurs through the fecal-oral route, from person to person, or by ingestion of contaminated food or drinking water.
- Approximately 1.4 million cases are reported each year, but the true incidence is thought to be 3 to 10 times higher due to the proportion of asymptomatic cases. (5) - Hepatitis A is most common in urban areas but the incidence rates differ according to geographical regions and socio-economic levels. - Hepatitis A vaccines are available.

WHAT IS IT?

Japanese encephalitis is a viral infection that was first observed in Japan in 1870. Japanese encephalitis is a vector-borne disease caused by an arbovirus transmitted by a mosquito.

With approximately 50,000 cases and 15,000 deaths reported each year, Japanese encephalitis is the most frequent and most severe viral encephalitis, and the leading cause of viral neurological infection among children in Asia. (11)

SYMPTOMS

- Encephalitis is the major form of the disease, although other, less severe forms, such as aseptic eningitis or simple febrile syndromes accompanied by headache, are also frequent.

- After an incubation period of 5 to 15 days, the disease is characterized by the abrupt onset of high fever accompanied by headaches, behavioral changes, as well as speech and motor disorders (paralyses).

- The evolution of the disease is marked by the gradual onset of consciousness disorders that can evolve to coma. The mortality rate of Japanese encephalitis is high and sequelae are common, especially among children (up to 50%).

- There is no specific treatment for the disease.

EPIDEMIOLOGY AND VACCINATION

- Japanese encephalitis is mostly seen in rural areas (where humans are in the close vicinity of swine and birds- the main reservoir of the virus), and more particularly in rice fields, an environment favorable to the development of mosquitoes.

- Infection usually occurs between April and December, with peaks during the monsoon season.

- Prevention is possible through the use of inactivated vaccines.

WHAT IS IT?

Yellow fever is a viral hemorrhagic fever that is transmitted by mosquitoes. Each year, 200,000 cases of yellow fever occur of which 30,000 are fatal. The disease is a threat for over 3 million travelers visiting. Endemic regions each year.

SYMPTOMS

- Following an incubation period of one week, the first signs of the disease typically include fever, chills, muscle pain, and headaches, suggestive of flu, dengue or malaria. In the most severe forms of the disease, a transient remission period occurs after 3 days, and is followed by the onset of a hemorrhagic syndrome associated with vomiting of black blood, jaundice (hence the name of the disease), and renal failure. - The outcome is fatal in 50 to 80% of cases. All curable forms of the disease confer lifelong immunity to the patients. - No specific antiviral treatment is available against yellow fever.

EPIDEMIOLOGY AND VACCINATION

- Although the usefulness of vaccination campaigns have been demonstrated to be beneficial over the past 60 years, yellow fever still remains a major concern in tropical regions in both Africa and South America. In countries at risk for yellow fever, vaccination is recommended in order to prevent and fight epidemics. It is also recommended for travelers visiting endemic regions.

WHAT IS IT?

Influenza, commonly known as flu, is an acute viral and highly contagious respiratory infection. Influenza viruses exhibit a high degree of variability. According to the extent of the genetic mutations from one year to another, the degree of protection of the population will vary and epidemics of variable intensity will occur. A pandemic can occur when a totally new influenza virus against which the human population has no immunity emerges, usually from animals.

SYMPTOMS

- After an incubation period of 1 to 5 days, the first symptoms begin to appear with the abrupt onset of fever accompanied by malaise, headaches, muscle pain, sore throat and non-productive cough. Infection usually lasts one week. Pneumonia is the most common complication and mostly occurs among young children, the elderly, and patients suffering from chronic diseases. Complications may lead to death, particularly among the most vulnerable groups. - Antivirals are available and are effective in reducing both the intensity and duration of symptoms provided they are administered early in the course of the disease.

EPIDEMIOLOGY AND VACCINATION

- Influenza viruses are transmitted from one person to another through the inhalation of respiratory droplets or contact with respiratory secretions. - According to World Health Organization (WHO) estimates, the number of influenza-related deaths range between 250,000 and 500,000 per year. - Several types of influenza vaccines are available. - Each year, the composition of influenza vaccines is adapted according to the dominant circulating strains.

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?

Mumps is caused by a virus exhibiting glandular and nervous tissue tropism. Although mumps is considered a rather benign childhood disease, in some instances it can result in severe complications.

SYMPTOMS

- After a mean incubation period of 15 days, mumps begins with general malaise and fever, followed by the swelling of the parotid (salivary) glands. Recovery is usually complete within approximately a week. - Complications such as aseptic meningitis, deafness, orchitis (inflammation of the testis), and pancreatitis may appear, especially among adults. - No specific treatment is currently available.

EPIDEMIOLOGY AND VACCINATION

- Mumps is a strictly human, highly contagious disease. - Transmission occurs through direct contact or inhalation of respiratory droplets from infected patients. Patients with mumps are contagious during the 2 days preceding the swelling of the salivary glands and up to 9 days following the onset of swelling. - In most regions throughout the world, the annual incidence of mumps is estimated between 100 and 1,000 cases per 100,000 people, with epidemic peaks occurring every 2 to 5 years. - Approximately 120 countries have already introduced mumps vaccination into their national immunization program.

WHAT IS IT?

Poliomyelitis is a contagious disease caused by three different serotypes of poliovirus (types 1, 2, and 3). It is responsible for incapacitating paralysis and death.

SYMPTOMS

- In most cases, the infected patient will remain asymptomatic or present only a flu-like syndrome similar to that observed with other benign viral infections. - In less then 1% of cases however, and after an incubation period ranging from several days to one month, incapacitating paralyses develop resulting in sequelae of various intensity and sometimes death. - No specific antiviral treatment is available.

EPIDEMIOLOGY AND VACCINATION

- Transmission is strictly humanto-human, and mainly fecal-oral. Whether symptomatic or not, an infected individual will transmit the virus to close contacts. - Polio still causes epidemic outbreaks in some countries in Sub-Saharan Africa, India, and the Middle East. - Two types of vaccine are being used to eradicate the disease: - Injectable inactivated polio vaccine (IPV), - Live attenuated oral polio vaccine (OPV). -After smallpox, poliomyelitis is projected to be the second infection eradicated from the surface of the earth.

WHAT IS IT?

Measles is an acute, viral, eruptive, and extremely contagious disease which affected practically all children prior to the introduction of vaccination. Today, measles is well controlled and has even been eliminated in many industrialized countries, but remains endemic in many other countries.

SYMPTOMS

- The incubation period is approximately 10 days. The disease is characterized by prodromal fever, conjunctivitis, coryza, cough, and Koplik spots on the buccal mucosa. - An erythematous rash appears between the 3rd and 7th day following onset of the first symptoms, beginning on the face and then spreading to the rest of the body. The rash lasts between 4 and 7 days, the first 4 to 5 of which the patients remains contagious. - Measles may be associated with severe complications such as otitis media, pneumonia, post-infectious encephalitis, and subacute sclerosing panencephalitis. - No specific treatment is available.

EPIDEMIOLOGY AND VACCINATION

- Measles is a strictly human disease responsible for an estimated 400,000 deaths each year, 90% of which occur in Africa and South-East Asia. (13-14) - The measles vaccine may be administered in combination with mumps and rubella vaccines (MMR vaccine). - Eradication of measles is theoretically feasible since the reservoir of the virus is exclusively human.

WHAT IS IT?

Rubella is an acute viral eruptive disease. It is not always symptomatic and goes unnoticed in about half of the cases. Rubella is particularly serious for a fetus when transmission of the virus by the mother occurs during the early stages of pregnancy, a condition known as congenital rubella syndrome or CRS.

 

SYMPTOMS

- The mean incubation period is 18 days. In its typical clinical form, the disease is characterized by a transient erythematous rash with moderate fever, conjunctivitis, coryza, and sub-occipital adenopathy (swelling of neck lymph nodes).

- In the case of CRS, infants develop ophthalmic, auditory, cardiac, and craniofacial malformations, which are more severe when transmission occurs early during pregnancy.

 

EPIDEMIOLOGY AND VACCINATION

- The rubella virus is transmitted from one person to another through respiratory droplets of infected subjects.

- Because the reservoir of the virus is exclusively human, eradication is theoretically possible.

- The rubella vaccine is often used in combination with measles and mumps vaccines (MMR vaccine).

- Within the past few years, vaccination has dramatically reduced, or even eliminated, rubella and CRS in many developed and some developing countries.

WHAT IS IT?

Varicella, better known as chicken pox, is a viral disease caused by the varicella-zoster virus. Although considered a benign childhood disease, varicella may be particularly severe in newborns, adults who have not contracted the disease during childhood, and immunodepressed individuals.

 

SYMPTOMS

- Following a mean incubation period of 15 days, moderate fever usually precedes the onset of a rash.

The first lesions usually appear on the face and scalp, before spreading to the trunk and the rest of the body. The initial macular (red spots) lesions subsequently become vesicular before drying out into scabs. Successive crops of lesions usually appear.

- The severe forms of the disease are treated using an antiviral.

 

EPIDEMIOLOGY AND VACCINATION

- The virus is transmitted through the respiratory route or by direct contact with the lesions. Patients are usually contagious several days before the onset of the rash and up to the formation of scabs.

- Varicella vaccines are available.