More background to pertussis with thanks to Dr Rupa Vora

• whooping cough is caused by Bordetella pertussis, a gram negative pleomorphic bacillus. It is spread by aerosol transmission and the bacteria cause damage by attaching to the respiratory cilia
• it occurs in clusters every 2-5 years during the summer months. We currently have an outbreak with the HPA provisionally reporting 665 cases in the first quarter of 2012 (cf. 1040 cases in 2011, 421 in 2010)
• cases have dropped dramatically since pertussis vaccinations have been introduced. Acellular pertussis vaccination is given at 2 and 3 months, followed by a pre-school booster.  However, protection wanes quickly and has virtually disappeared by 12 years old
• incubation period is 3-12 days and children are most infectious in the first 2-3 weeks. They are most likely to present in the second phase of illness at 3-4 weeks
• can present with coryza (1^st stage which lasts a couple of weeks), paroxysms of cough, difficulty feeding and pneumonia. Younger infants (<6months) may not present with the characteristic ‘whoop’. Older children and adults often present with a persistent cough
• complications include chronic cough (“100 day cough”), hypoglycaemia, seizures, encephalopathy and intracranial haemorrhage
• any infant is vulnerable and up to 50% may need hospitalisation.  Especially vulnerable are ex-prems and those with underlying cardiology, respiratory or neurological problems.  
• In England and Wales, whooping cough is statutorily notifiable.  The diagnosis is usually made on clinical grounds without the requirement for laboratory confirmation
• The UK Health Protection Agency advises a 7 day course of erythromycin or clarithromycin (or azithromycin for 3-5 days if under 4 weeks) to reduce spread.  A pernasal swab to confirm or refute B. pertussis as the causative organism can be carried out.  If the cough has been present for more than two weeks and the child is in the community, serum serology can be sent to Colindale.  See table below:

Appropriate laboratory tests for a sporadic case of pertussis reported to HPA on clinical suspicion (with thanks to Dr Maria O’Callaghan): 

 NPA – nasopharyngeal aspirate; PNS – pernasal swab;

RSIL – Respiratory and Systemic Infections Laboratory, Colindale

Useful websites:

HPA: www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/WhoopingCough/

NHS Choices: www.nhs.uk/Conditions/Whooping-cough/Pages/Introduction.aspx