Tag Archives: Zika

Infection Sensitisation

A previous News Blog [1] discussed the finding that a previous infection with one strain of Dengue fever can sensitise a person so that infection with a second strain will be more severe than would otherwise have been the case. There is new evidence that such Antibody Dependent Enhancement (ADE) may cross species barriers, such that a person sensitised with one type of flavivirus, say Dengue, is more likely to have a severe illness if inflected with another flavivirus, such as the Zika virus.[2] Such cross species ADE has obvious implications for vaccination programmes. In previous News Blogs [3] we have drawn attention to cross-resistance such that vaccines protect against non-target organisms (e.g. small pox vaccines provide protection against HIV). The above paper shows that the reverse can also occur. This is not the first time that vaccination has been shown to have adverse consequences.[4]

— Richard Lilford, CLAHRC WM Director

References:

  1. Lilford RJ. Three hits hypothesis. NIHR CLAHRC West Midlands News Blog. 7 April 2017.
  2. Cohen J. Dengue may bring out the worst in Zika. Science. 2017; 355(6332): 1362.
  3. Lilford RJ. Two papers try to answer the question – do vaccinations for one communicable disease offer protection against others? NIHR CLAHRC West Midlands News Blog. 27 January 2017.
  4. Guzman MG, Alvarez M, Halstead SB. Secondary infection as a risk factor for dengue hemorrhagic fever/dengue shock syndrome: an historical perspective and role of antibody-dependent enhancement of infection. Arch Virol. 2013; 158(7): 1445-59.
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Update on Zika for News Blog Readers

A recent review of epidemiological evidence from the Center for Disease Control (CDC) in Atlanta confirms the association of Zika arbovirus infections during pregnancy with microcephaly in the infant, with a risk of about one in 100.[1] It is probable that the risk of neurological effects less serious than microcephaly is also increased. A recent BMJ paper [2] analyses a cohort of microcephalic children born of mothers with Zika virus infection in pregnancy. They did not just measure the size of the head relative to length and weight. All babies underwent CT scan, MRI, or both. They all manifested strikingly similar features on neuro-imaging, and these features are largely distinct from the other known causes of microcephaly, including those associated with infections with other viruses, such as cytomegalovirus. The famous philosopher of science William Whewell, argued that if information of different types all corroborate the same theory, then that is powerful support in its favour.[3] The CLAHRC WM Director thinks a causal role for the virus is pretty much settled – we may assume that the Zika virus is indeed a cause of severe (and perhaps less severe) neurological damage in the foetus.

— Richard Lilford, CLAHRC WM Director

References:

  1. Rasmussen SA, Jamieson DJ, Honein MA, Petersen LR. Zika Virus and Birth Defects — Reviewing the Evidence for Causality. N Engl J Med. 2016; 374: 1981-7.
  2. Aragao MFV, van der Linden V, Brainer-Lima AM, et al. Clinical features and neuroimaging (CT and MRI) findings in presumed Zika virus related congenital infection and microcephaly: retrospective case series study. BMJ. 2016; 353: i1901.
  3. Whewell W & Butts RE. William Whewell’s Theory of Scientific Method. Pittsburgh: University of Pittsburgh Press. 1968.