Two weeks ago, in Netherlands: RIVM Reports Patient With Severe Swine Variant (H1N1) Infection, we looked at a brief report on a recent severe infection with an H1N1v (swine variant) virus in a child with swine exposure.
This year we've also seen 23 - mostly mild or moderate - swine variant flu infections reported in the United States, the largest number since 2012.
While avian influenza currently has most of our attention, the evolution of influenza A viruses in pigs remains a serious concern. First some excerpts from today's Eurosurveillance Report, then I'll have a bit more.
Eurosurveillance, Volume 21, Issue 48, 01 December 2016
Severe acute respiratory infection caused by swine influenza virus in a child necessitating extracorporeal membrane oxygenation (ECMO), the Netherlands, October 2016
Correspondence: Pieter L. Fraaij (firstname.lastname@example.org)
Citation style for this article: Fraaij PL, Wildschut ED, Houmes RJ, Swaan CM, Hoeben CJ, de Jonge HEC, Tolsma P, de Kleer I, Pas SD, Munnink BBO, Phan MV, Bestebroer TM, Roosenhoff RS, van Kampen JJ, Cotten M, Beerens N, Fouchier RA, van den Kerkhof JH, Timen A, Koopmans MP. Severe acute respiratory infection caused by swine influenza virus in a child necessitating extracorporeal membrane oxygenation (ECMO), the Netherlands, October 2016. Euro Surveill. 2016;21(48):pii=30416. DOI: http://dx.doi.org/10.2807/1560-7917.ES.2016.21.48.304160
Received:14 November 2016; Accepted:30 November 2016
In October 2016, a severe infection with swine influenza A(H1N1) virus of the Eurasian avian lineage occurred in a child with a previous history of eczema in the Netherlands, following contact to pigs. The patient’s condition deteriorated rapidly and required life support through extracorporeal membrane oxygenation. After start of oseltamivir treatment and removal of mucus plugs, the patient fully recovered. Monitoring of more than 80 close unprotected contacts revealed no secondary cases.
We here report a patient with severe acute respiratory infection as a result of swine influenza virus (SIV) infection in the Netherlands.
A school-aged patient with a previous history of mild eczema developed a respiratory tract infection in October 2016, a couple of days after visiting a pig farm. The child had entered the pigsty but had not been in direct contact with pigs. Despite early prescription of antibiotics by the general practitioner the child’s clinical situation rapidly deteriorated.
Within three days after onset of disease the child was transferred to a paediatric intensive care unit (PICU) for non-invasive ventilation support and intensive monitoring. Despite these efforts, the patient deteriorated further and was intubated in order to start mechanical ventilation. Bronchoscopy following intubation revealed large amounts of highly viscous mucus in the airways.
Efforts to remove this mucus failed to improve ventilation. Mechanical ventilation became increasingly complex and it was decided to initiate veno-venous extracorporeal membrane oxygenation (ECMO) and to transfer to a quaternary PICU. Due to ECMO, blood oxygenation was secured and extensive bronchoscopy could be performed, during which topical DNAse (Dornase alpha, Pulmozyme, Roche) was instilled to decrease viscosity and facilitate removal of obstructing mucus plugs. On the following day, bronchoscopy was repeated and additional mucus was removed.
In the days following these procedures, the patient improved rapidly. ECMO was discontinued five days after start and the patient could be extubated. For the entire duration of hospitalisation, the patient had received broad-spectrum antibiotics, although all bacterial cultures remained negative.
Throat swabs had been collected at initial admission and tested positive for influenza A virus, of which the quaternary PICU was informed on the day after the patient transfer. Oseltamivir treatment (60 mg twice daily) was started hours after initiation of ECMO and transport. It was continued for a total of 7 days when a nasal swab tested negative for influenza virus. At the time of submission of this report, the child was recovering well.
Swine variant viruses continue to spread and evolve around the world, and while surveillance is non-existent in many regions, we manage to keep an eye on several different lineages.
Last December, in PNAS: The Pandemic Potential Of Eurasian Avian-like H1N1 (EAH1N1) Swine Influenza, we looked at the isolation and characterization of a number avian H1N1 virus variants circulating in Chinese pigs that researchers there believe have considerable pandemic potential.
In the `Significance' section the authors boiled it down to this:
Here, we found that, after long-term evolution in pigs, the EAH1N1 SIVs have obtained the traits to cause a human influenza pandemic.
Similarly, in August of 2015, we looked at a study that examined two recently discovered swine variant strains (see J. Virol: Novel Reassortant Human-like H3N2 & H3N1 Influenza A Viruses In Pigs) in North America. They described both of these novel subtypes as:
“. . . virulent and can sustain onward transmission in pigs, and the naturally occurring mutations in the HA were associated with antigenic divergence from H3 IAV from human and swine’” and goes on to warn that ``. . . the potential risk of these emerging swine IAV to humans should be considered”.
And just last October, in MMWR: Investigation Into H3N2v Outbreak In Ohio & Michigan - Summer 2016, we looked at the CDC's investigation into a cluster of 18 H3N2v cases across two states during the month of August. This was the biggest outbreak of swine variant infections we'd seen since 2012, when more than 300 cases were reported across 10 states.
The `headline' in that report was that 16 of the 18 cases analyzed belonged to a new genotype not previously detected in humans.
Swine influenza viruses – while usually less virulent than avian flu - are worrisome because they are already adapted to mammals, and are believed to have less of a `leap’ to make in order to adapt to humans.
For more on swine as potential `flu factories’, you may wish to revisit: