Friday, March 23, 2018

Netherlands Reports A Reassorted H1N2 Flu Virus


Influenza reassortment - also known as Antigenic Shift - is something we've discussed often in the blog, albeit mostly in birds, swine, and other mammals.  This reshuffling of influenza genes is the primary force behind the creation of novel or pandemic flu (see NIAID Video: How Influenza Pandemics Occur).
While less commonly reported in humans, as any virologist will tell you; shift happens. 
A couple of months ago, in Double-Whammied By Influenza, we looked at the relatively common occurrence of human dual infection with two types of flu - the prerequisite for reassortment.

The biggest concern is of seeing a humanized (H1N1 or H3N2) influenza virus reassort with a novel flu, like H7N9 or H5N1, potentially producing a highly virulent and easily transmitted hybrid.  
While we've seen co-infections (see Lancet: Coinfection With H7N9 & H3N2), a viable novel-seasonal reassortment has not emerged.
While rare, the same can not be said for reassortments between seasonal flu subtypes.
In 1988-1989 in China (see Human influenza A (H1N2) viruses isolated from China), and again between 2000 and 2003 in the Northern Hemisphere, we saw the brief appearance of a human H1N2 virus - a reassortment between seasonal H1N1 and H3N2.
While a minor player in most regions, H1N2 was the predominant Influenza A(H1) virus reported during the UK's 2001–02 influenza season (cite).
These were human-origin H1N2 viruses, not to be confused with the swine-origin variant H1N2 viruses that have circulated in pigs for decades and that we've seen occasionally jump to humans over the past decade.

From a 2014 EID Journal article -  A Historical Perspective of Influenza A(H1N2) Virus - we learn that this reassorted virus vanished in early 2003, as suddenly as it arrived:
By early 2003, A(H1N2) viruses were no longer being isolated from human samples. In 2006, an A(H1N2) virus that was a triple reassortant-like virus and, with the exception of the matrix gene, genetically similar to A(H1N2)pdm09 viruses, was isolated from swine in China (41).
In late 2009, a novel A(H1N2) virus was isolated from a human in India (5). This H1N2 virus was a reassortant of A(H1N1)pdm09 and A(H3N2) viruses co-circulating in the population. Although this virus had a similar genetic makeup to previously observed A(H1N2) viruses, the source of the HA component differed and was derived from the A(H1N1)pdm09 virus (5).

While ultimately unable to compete against the more biologically `fit' wild H1N1 and H3N2 viruses, both of these incidents suggest H1N2 wasn't that far off the mark.  It obviously transmitted well enough in China and the UK to become - at least for a time - widespread. 
As noted above, rare `one-offs' of H1N2  have been detected in recent years, but we've seen no signs of ongoing transmission.
In late 2016, in EID Journal: Characterization of a Novel Human Influenza A(H1N2) Virus Variant, Brazil, we looked at a triple reassortant H1N2 variant with genetic contributions from swine H1N2 (hemagglutinin), H3N2 (neuraminidase), and pandemic H1N1 (remaining genes) in a teenage pig farm worker. 
All of which brings us to a report today from the Netherlands of a single detection of a reassorted H1N2 virus in a hospitalized patient, who has since recovered. 
This report from NIVEL (Dutch Institute For Health Services Research).

New variant flu virus found

In the Netherlands, it has been found a particularly influenza virus in a general medical practice; a new strain of influenza A (H1N2). The patient was seriously ill and has been restored. The doctor took a nose and throat of sample for influenza surveillance NIVEL Care Records - sentinel. There are no other patients were found with the virus.
The new flu virus consists of parts of two currently circulating influenza viruses. Probably someone infected with both viruses and is hereby created a new combination. This is called a reassortant virus. It's not very common that a reassortant virus, but happens often. Researchers do not expect this virus makes people more ill or can spread faster than the regular flu viruses now. The flu shot this season probably provides protection against this variant.

General complaints

The patient visited in early March 2018 a doctor who participates in the sentinel stations of NIVEL Care Registrations first line . These GPs report weekly on people with flu-like symptoms and taking nose and throat samples off at some of these patients. These samples are sent to the RIVM laboratory for research on viruses that can cause flu-like symptoms. In the laboratory and confirmed by further research at the Erasmus Medical Center found the patient to wear a new strain of influenza virus with them. The patient had general flu-like symptoms such as fever, cough, shortness of breath, sore throat and diarrhea. The patient has fully recovered and is no longer contagious.
Further research

in order to identify possible spread family members are investigated if they develop flu-like symptoms. Within that general practice in the Netherlands and elsewhere are no other infections this flu virus found. According to protocol also informed the health authorities, laboratories and international organizations on this finding.

Peilstations NIVEL care registrations

NIVEL care registrations first line makes use of data which are collected routinely in the care sector at different primary disciplines. Including at nearly 500 general practices with over 1.8 million registered patients. Over forty of these practices - the sentinel stations - also report weekly on the occurrence of a number of diseases, events and transactions that are missing from routine records and are not easy to include, such as influenza. These sentinel existence since 1970.

More information
12th newsletter influenza season 2017-2018
RIVM new flu virus
Frequently asked questions about the new flu virus

While likely a one-off, H1N2 has shown enough tenacity in the past that we'll be keeping out eye out for more reports in the months ahead.

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