H. influenzae type B can cause life-threatening infection of the epiglottis, a condition that is rare over the age of 5 years. The young child becomes extremely ill with a high fever, and severe airflow obstruction may rapidly occur. This is a life-threatening emergency and requires urgent edotracheal intubation and intravenous ceftazidime (25-150 mg kg-l in children). Chloramphenicol (SOlDO mg kg-l in children) can also be used. The epiglottis, which is red and swollen, should not be inspected until facilities to maintain the airways are available. Other manifestations of H. influenzae type b (Hib) are meningitis, septic arthritis and osteomyelitis. All can be prevented by immunization with a purified polyribosylribitol phosphate from the capsule of Hib linked to a non-toxic diphtheria toxin PRP- T to increase immunogenicity. It is highly effective when given to infants at 2, 3 and 4 months with primary immunization against diphtheria, tetanus and pertussis (DTP) reducing death rates from Bib infections virtually to zero.
• Influenza
The influenza virus belongs to the orthomyxovirus group and exists in two main forms-A and B. Influenza B is associated with localized outbreaks of milder nature, whereas influenza A is the cause of worldwide pandemics. Influenza A has a capacity to develop new antigenic variants at irregular intervals. Human immunity develops against the haemagglutinin (H) antigen and the neuraminidase (N) antigen on the viral surface. Major shifts in the antigenic make-up of influenza A viruses provide the necessary conditions for major pandemics, whereas minor antigenic drifts give rise to less severe epidemics because immunity in the population is less blunted. The most serious pandemic of influenza occurred in 1918, and was associated with more than 20 million deaths worldwide. More recently, in 1957, a major shift in the antigenic make-up of the virus led to the appearance of influenza A2 type H2-N2, which caused a worldwide pandemic. A further pandemic occurred in 1968 owing to the emergence of Hong Kong influenza type H3-N2, and minor antigenic drifts have caused outbreaks around the world ever since.
CLINICAL FEATURES
The incubation period of influenza is usually 1-3 days. The illness starts abruptly with a fever, shivering and gen- .eralized aching in the limbs. This is associated with severe headache, soreness of the throat and a persistent dry cough that can last for several weeks. Influenza viruses can cause a prolonged period of debility and depression that may take weeks or months to clear; this is known as the postviral syndrome.
COMPLICATIONS
Secondary bacterial infection, particularly with Strep. pneumoniae and H. influenzae, is common following influenza virus infection. Rarer, but more serious, is the development of pneumonia caused by Staph. au reus, which has a mortality of up to 20%. Postinfectious encephalomyelitis rarely occurs after infection with influenza virus
DIAGNOSIS
Laboratory diagnosis of all cases is not necessary. Definitive diagnosis can be established by demonstrating a fourfold increase in the complement-fixing antibody or the haem agglutinin antibody when measured before and after an interval of 1-2 weeks. Viral cultures are still a research procedure.
TREATMENT
Treatment is bed rest and aspmn, together with antibiotics for individuals with chronic bronchitis, or heart or renal disease.
PROPHYLAXIS
Protection by influenza vaccines is only effective in up to 70% of people and is of short duration, usually lasting for only a year. Influenza vaccine should not be given to individuals who are allergic to egg protein as some are manufactured in chick embryos. New vaccines have to be prepared to cover each change in viral antigenicity and are therefore in limited supply at the start of an epidemic. Routine vaccination is reserved for susceptible people with chronic heart, lung or kidney disease, and the elderly. In pandemics key hospital and health service personnel are also vaccinated.
Amantadine hydrochloride 100-200 mg daily may attenuate influenza A infection and should be reserved for individuals with chronic respiratory or cardiovascular disease who have not previously been immunized. Inhalation of foreign bodies Children inhale foreign bodies, frequently peanuts, more commonly than adults. In the adult, inhalation often occurs after an excess of alcohol or under general anaesthesia (loose teeth or dentures).
When the foreign body is large it may impact in the trachea. The person chokes and then becomes silent; death occurs unless the material is quickly removed.
Impaction usually occurs in the right main bronchus and produces:
• Choking
• Persistent monophonic wheeze
• Later, persistent suppurative pneumonia
• Lung abscess (common)
