WER: Update On Human Cases Of Influenza At Human-Animal Interface

H5N1 activity by year – Credit WER

 

 

# 8825

This week the World Health Organization’s Weekly Epidemiological Record (WER) is devoted to a detailed review of human infections by novel (swine & avian) flu viruses over the course of 2013.

As in the past, a good deal of time is spent on the H5N1 virus, but last year also saw the emergence of a new contender for the dominant avian flu throne – H7N9 -  the return of H3N2v and H1N1v swine variant flu viruses, a smattering of H7 cases, H9N2, and the surprise human infections from H6N1 and H10N8 detected in Taiwan and China.

 

The formatting of the WER is such that it is far more practical for you to download and read the PDF file than for me to try to reproduce it here, so I’ll simply provide a link.

 

Human cases of influenza at the human–animal interface, 2013

11 July 2014, vol. 89, 28 (pp. 309–320) 11 July 2014

Issues of the WER are in Adobe™ Acrobat™ portable document format (.pdf). To view the WER, the programme Acrobat Reader is required.

WHO Avian Flu Risk Assessment - December

Seasonality of H5N1 – Credit WHO

 

# 8081

 

 

With winter setting in the northern hemisphere, and two novel avian flu viruses (H5N1 & H7N9) in circulation, it is a pretty good bet that we will be hearing about increased outbreaks in poultry, and scattered human infections, over the coming months.

 

If fact, it would be a big surprise if we didn’t see more cases over the next 5 or 6 months.  As the chart at the top of this blog indicates, avian influenza cases historically go up during the winter and spring.

 

Whether any of these outbreaks will lead to a larger public health concern, remains to be seen.  But right now, neither of these viruses has demonstrated the ability to spread efficiently from human-to-human.  That could change over time, of course, which is why we watch these cases carefully for any signs the virus is better adapting to human physiology.

 

The World Health Organization has released their monthly Influenza at the human - animal interface report, dated December 10th,  2013, which reviews the avian flu activity over the previous month, and looks ahead to what we might see over the winter.

 

Influenza at the human-animal interface 
Summary and assessment as of 10 December 2013

Human infection with avian influenza A(H5N1) viruses 

From 2003 through  10  December  2013,  648  laboratory-confirmed human cases with avian influenza A(H5N1) virus infection have been officially reported to WHO from 15 countries. Of these cases, 384 died.

Since the last WHO Influenza at the Human Animal Interface update on 7 October 2013, seven new laboratory-confirmed human cases of influenza A(H5N1) virus infection were reported to WHO from Cambodia (6) and Indonesia (1). 

In Cambodia, the reported incidence of human cases has increased in 2013 (26 cases in 2013 compared with 21 cases from 2005 through December 2012). This might be due to improvements in surveillance and physician awareness or to a potential increased circulation of the virus in poultry. The case fatality rate among reported cases, however, has decreased (54% in 2013 compared with 90% over all previous years).

Before 2013, H5N1 viruses from clade 1.1 predominated in Cambodia. Analysis of isolates from human cases and birds from the beginning of 2013 revealed the emergence of a new H5N1 genotype resulting from the reassortment of clade 1.1 and clade 2.3.2.1 viruses.

The link between the emergence of this reassortant virus and the increase in human cases observed in 2013 is yet to be determined.

All seven human cases reported in this summary are considered to be sporadic, with no evidence of  community-level transmission. As influenza A(H5N1) virus is thought to be circulating widely in poultry in Cambodia and Indonesia, additional sporadic human cases or small clusters might be expected in these countries in the future.

Overall public health risk assessment for avian influenza A(H5N1) viruses: Whenever influenza viruses are circulating in poultry, sporadic infections or small clusters of human cases are possible, especially in people exposed to infected household poultry or contaminated environments. However, this influenza A(H5N1) virus does not currently appear to transmit easily among people. As such, the risk of community-level spread of this virus remains low. 

Human infection with other non-seasonal influenza viruses

Avian influenza A(H7N9) in China

Since the last update of 7 October 2013, China has reported six new cases of human infection with avian influenza A(H7N9) virus, from Zhejiang (5) and Guangdong (1) provinces, with onset dates between 8 October and 29 November. In addition, the Centre for Health Protection, China, Hong Kong SAR has reported two human cases, one with an onset date of 21 November 2013 and the other with onset at  the beginning of December. Both cases had been in Guangdong province in China in the week before clinical onset. Most patients presented with pneumonia.

 

Most human A(H7N9) cases have reported contact with poultry or live bird markets. Knowledge about the main virus reservoirs and the extent and distribution of the virus in animals remains limited and, because this virus causes only subclinical infections in poultry, it is possible that the virus continues to circulate in China and perhaps in neighbouring countries without being detected. As such, reports of additional human cases and infections in animals would not be unexpected, especially with onset of winter in the Northern Hemisphere.

Although five small family clusters have been reported (including one among recent reported cases in Zhejiang province), evidence does not support sustained human-to-human transmission of this virus.

Overall public health risk assessment for avian influenza A(H7N9) virus: Sporadic human cases and small clusters would not be unexpected in previously affected and possibly neighbouring areas/countries of China. The current likelihood of community-level spread of this virus is considered to be low.

 

Continued vigilance is needed within China and neighbouring areas to detect infections in animals and humans. WHO advises countries to continue surveillance and other preparedness actions, including ensuring appropriate laboratory capacity. All human infections with non-seasonal influenza viruses such as avian influenza A(H7N9) are reportable to WHO under the IHR (2005). 

 

 

The bottom line – particularly for those who were not following H5N1 in the `wild days’ of 2005-2008 - is that sporadic cases - and even a few clusters of cases - don’t tell us a whole lot about where any novel influenza virus is headed.  The dramatic outbreaks in Indonesia, Turkey, and Vietnam in the middle of the last decade taught us that much.

 

If the transmissibility of avian flu among humans changes, I fully expect the WHO and the newshounds of Flublogia will pick up on it fairly quickly.  For now, that doesn’t appear to be the case.

 

In the meantime, we should not be surprised to see a steady parade of scattered avian flu reports over the next few months. While a personal tragedy for those affected – and a serious concern to local public health authorities -  they do give us an opportunity to better study and understand the virus, and how it spreads.

 

Something that could pay big dividends if either virus ever adapts successfully to humans.

WER: Update On Human Cases Of Influenza At Human-Animal Interface

 

# 7041

 

This week the World Health Organization’s Weekly Epidemiological Record (WER) is devoted to a review of human infections by novel (swine & avian) flu viruses over the course of 2012. 

 

The bulk of this epidemiological analysis focuses on the 32 lab-confirmed H5N1 cases reported last year, but attention is also paid to a pair of H7N3 last year in Mexico, and a spate of swine H1N1v, H1N2v, and H3N2v (variant) infections across North America, as well.

 

 

The full report is called: 

 

Update on human cases of influenza at the human–animal interface, 2012

This report describes the epidemiology of the 32 laboratory-confirmed human infections with highly pathogenic avian influenza (H5N1) virus that were reported to WHO from 6 countries during 2012, and summarizes the information on other zoonotic influenza infections – A(H3N2) variant, A(H1N1), A(H1N2) and A(H7N3) – reported in 2012 in humans.

 

Some highlights follow regarding the H5N1 virus (slightly reparagraphed for readability):

 

The epidemiological curve of human cases follows the same seasonal pattern seen in previous years, with larger numbers of cases in the months December to March (Figure 1). This curve follows the seasonal curve  of reported outbreaks in poultry. Of the human cases for the year, 72% (23/32 cases) were reported in the first 3 months of 2012 (1 January to 31 March).

Distribution by age and sex

In 2012, most cases occurred in children and young adults; 90% (29/32) were in people aged <40 years and 34% (11/32) in children aged <10 years. Cases ranged in age from 6 months to 45 years, with a median age of 18 years.

 

The median age of reported cases has varied annually since 2009: 5 years of age in 2009, 25 years in 2010 and 13 years in 2011. The median age of cases in Egypt remained high for the third consecutive year.

 

The median age in Egypt in 2009 was 3 years but rose to 27 years in 2010 and 21 years in 2011 and continued to increase in 2012 to 31 years. In 2012, Egypt reported fewer cases of H5N1 infection (11 cases) compared with previous years (39 cases in 2011, 29 cases in 2010, 39 cases in 2009).

 

In the past few years, the trend in Indonesia has been towards progressively younger cases. In 2012, the median age was 12 years, up from 8 years in 2011, but considerably down  from 34 years in 2010 and 20 for 2005–2011. Indonesia also reported a relatively low number of human cases in 2012: 9 cases were reported in 2012, 12 cases in 2011, 9 cases in 2010 and 21 cases in 2009, compared with 55 cases reported in 2006.

 

In 2012, equal numbers of male and female cases were reported overall, although this pattern was not uniform across countries or age groups. The sex difference was most prominent in Egypt where 82% (9/11) of cases were female. Data from all cases reported during 2003– 2012 show a similar 1:1.2 male:female ratio.

 

Clinical outcome

In 2012, the overall proportion of fatal cases among
those reported was 62.5% (20/32), slightly higher thanin the previous 3 years (55% in 2011, 50% in 2010, 44% in 2009) but similar to the average of all cases reported to WHO since 2003 (59% [360/610]). The proportion of confirmed cases with fatal outcomes varied among countries and age groups. The proportion of fatal cases among those reported was 100% in Indonesia (9/9) and Cambodia (3/3), and 0 (0/3) in Bangladesh. Considerable differences were also found across age groups.

While the number of confirmed human infections with the H5N1 virus have declined over the past several years, this report cautions:

Although the proportion of reported fatal human cases remains high, the finding of 3 human cases in 2012 with mild infection reinforces concerns that many milder cases of infection occur undetected. Recent reviews of H5 seroprevalence studies found little evidence that large numbers of cases of H5N1 infection are missed.12, 13

 

However, because of the variation in protocols and standards in the serological studies, as well as persistent questions about serological responses in exposed or infected humans, the frequency of subclinical infection or mild illness remains uncertain.

 

It is also likely that some severe and fatal cases were not diagnosed and thus missed.

The risks posed by the H5N1 virus, along with other emerging influenza viruses, remains very real.  In the discussion portion of this report, the authors write:

 

Influenza viruses are unpredictable. Their constant evolving nature raises concerns that these viruses could adapt or reassort with other influenza viruses, thereby gaining potential to become more transmissible to or more pathogenic in humans.

 

Continued monitoring of the occurrence of human infections with non-seasonal influenza viruses and ongoing characterization of the viruses to assess their pandemic risk are therefore critically important for public health.

 

Close collaboration with animal health partners allows information regarding viruses circulating in animal populations and human populations worldwide to be shared to improve assessment of global influenza risks to health.

 

WHO continues to stress the importance of global
monitoring of influenza viruses and recommends all
Member States to strengthen routine influenza surveillance. All human infections with non-seasonal influenza viruses should be reported to WHO under the International Health Regulations (2005).

A WHO Flu Review

 

 

 

# 6602

 

Each month the World Health Organization releases a Monthly Risk Assessment Summary on influenza at the human-animal interface. 

 

That is, influenza viruses that currently reside primarily in non-human hosts, but pose a threat of jumping to humans.

 

With the Northern Hemisphere flu season soon upon us, conditions for the spread of influenza viruses grow more favorable.  So today, some excerpts from the latest assessment from the WHO.

 

Influenza at the human-animal interface

Summary and assessment as of 10 September 2012

Human infection with avian influenza A(H5N1) virus and associated animal health events

From 2003 through 10 September 2012, 608 laboratory-confirmed human cases with avian influenza A(H5N1) virus infection have been officially reported to WHO from 15 countries, of which 359 died. 

Since January 2012, 30 human cases of influenza A(H5N1) virus infection have been reported to WHO.
Since the last update, no new laboratory-confirmed human cases with influenza A(H5N1)virus infection
were reported to WHO.

 

The epidemiologic curve of recent human cases (Figure 1) follows the same pattern seen in previous
years, with larger numbers of cases in the winter months, decreasing towards summer in the northern
hemisphere. This curve follows the seasonal curve of outbreaks in birds.

 

An increase in the number of H5N1 poultry outbreaks would be expected to occur over the coming
months, with the arrival of winter, and there are indications that the normal seasonal increase in
outbreaks in poultry in endemic countries is beginning. Human infections can be expected any time the virus is circulating in poultry.

Human infection with other non-human  influenza viruses

A(H3N2) variant virus infection

The United States of America (USA) continues to report an increase in the number of human cases of
A(H3N2)v virus infection. The recent increase in cases is likely due to an increased exposure associated with numerous state and local agricultural fairs and events, and improvements in testing protocols, including improved diagnostic protocols and testing of the contacts of patients.

 

Up to 7 September, 16 human cases have been hospitalized as a result of their illness and one H3N2v-associated death has been reported. The large majority of cases have been associated  with swine exposure though instances of likely human-to-human  transmission have been identified.

 

No sustained human-to-human transmission has been reported. Limited serological studies indicate that adults may have some pre-existing immunity to this virus but children do not. Seasonal vaccines do not provide cross-protection to influenza A(H3N2)v in adults or children. WHO has identified several candidate vaccine viruses specific for A(H3N2)v that could be used to produce an (H3N2)v vaccine if needed.

Overall public health risk assessment for influenza A(H3N2)v viruses : Further human cases and small
clusters may be expected as this virus is circulating in the swine population in the USA and people may
continue to be exposed, especially through the fall. Close monitoring of the situation is warranted as
schools have started again and changing weather conditions may favor influenza transmission.

 

A(H1N2) variant virus infection

As a result of enhanced surveillance around the animal fairs, 3 human cases of infection with H1N2
variant influenza virus were detected and reported  from the USA. The cases occurred in a previously
healthy adult, a child with asthma and an elderly person with diabetes. All 3 had prolonged contact with swine at the State fair in Minnesota, USA. All recovered from their illness. The viruses isolated have an hemagglutinin similar to human seasonal influenza viruses circulated in people as recently as 2007, which might suggest some existing population immunity except in young children. Available data
indicates that the virus would be susceptible to the antivirals (neuraminidase inhibitors; oseltamivir and
zanamivir). Investigation around these cases is ongoing.

 
Overall public health risk assessment for influenza A(H1N2)v viruses : Further human cases and small
clusters of human infection with the virus may be expected as this virus is circulating in the swine
population in the USA.

 

A(H7N3) influenza virus infection

Two cases of human infection with avian influenza A(H7N3) virus were reported from Mexico. The two
cases presented with conjunctivitis without fever or respiratory symptoms and fully recovered. Both
cases were exposed while working on a farm where poultry was infected with H7N3. No further
epidemiologically linked human cases have been reported. Sporadic human cases of influenza A(H7N3) virus infection linked with outbreaks in poultry have been reported previously in Canada, Italy and the UK, with H7N2 in US and the UK, and with H7N7 in the UK and the Netherlands. Most H7 infections in humans have been mild with the exception of one fatal case in the Netherlands, in a veterinarian who had close contact with infected birds.

 

Overall public health risk assessment for influenza H7N3 viruses: Further human cases and small
clusters may be expected as long as the virus is circulating in poultry. Countries experiencing outbreaks of influenza virus infection in animals should implement appropriate biosafety measures to protect people working with or living nearby infected and potentially infected animals. Collaboration with animal health partners is necessary to optimally control this disease and decrease risks to public health.

 

Because influenza viruses evolve constantly and change characteristics and behavior unpredictably, WHO continues to stress the importance of global monitoring of variant influenza viruses and recommends to all Member States to strengthen routine surveillance activities. 

 

 

Not mentioned in this report is The Return Of H1N1v in Missouri and in Ontario, as both reports came after its release date. 

 

As I discussed a month ago in An Increasingly Complex Flu Field, the past few years have seen an expansion of the number of zoonotic influenza threats, particularly from avian and swine hosts.

 

 

And there are other flu threats out there, that have yet to infect man, but are worthy of our attention.  One of those was detected in more than a hundred dead seals last year along the New England coastline (see mBio: A Mammalian Adapted H3N8 In Seals).

 

For now, there are no signs that we are on the verge of another pandemic. 

 

But the fact remains these viruses continue to change and evolve, and the threat they may pose tomorrow, next month, or next year could differ from threat they pose today.