Tuesday, November 22, 2005

ProMED round up on avian influenza in Canadian birds (domestic and wild)

ProMED had a couple stories on the findings of low pathogenic avian influenzas in Canada.

Here is a snippet:

Tests revealed low pathogenic strains of H5N9 in 2 birds and H5N2 in
5 birds in the western province of British Columbia, H5N1 in 2 birds
from the central province of Manitoba and H5N3 in 2 birds from the
eastern Quebec province, officials said.

(original source here)

Damien

Saturday, November 19, 2005

CP: H5N1 avian flu viruses found in Manitoba, but not Asian form of virus: source

Two of the wild "ducks" in the 2005 Interagency Wild Bird Influenza Survey have turned out to be low pathogenic H5N1 ( story):

TORONTO (CP) - The Canadian Press has learned wild ducks in Manitoba have tested positive for H5-N1 avian flu viruses, but not the dangerous form of the virus circulating in Southeast Asia.

The findings will be reported by federal officials at a news conference Saturday afternoon.


Specifically,

the genetic code of the two proteins on the surface of the Manitoba H5-N1 viruses have confirmed these viruses are from the family of North American H5-N1 viruses, not the strains circulating in Southeast Asia

Damien

CTV: H5 bird flu found in B.C. duck; strain uncertain

Story here, and press release from the BC Ministry of Agriculture here.

According to a post on CurEvents, the H5 positive duck was from a free-ranging duck farm (no idea if this is true). It will be interesting to learn whether this appearance of H5 is related to the presence of H5 in wild waterfowl. If so, this event underscores the need for biosecurity on poultry farms, whether in Asia or North America. Once again, we are seeing the importance of controlling disease at the livestock, wildlife and human health interface (boy, readers of this blog must get tired of me writing this!)

We should hear in a week or so what the neuraminidase subtype is.

Damien

Friday, November 18, 2005

Please support ProMED

Click here to support ProMED.

Here is commentary from Michael Osterholm, Director of the Center for Infectious Disease Research and Policy:

"I just went online and made my contribution to the ProMED
Internet-a-thon. But I'd be remiss if I didn't also take
time to thank you and the other editors for your wonderful
and invaluable service. I can't imagine a world today
without ProMED. You are an invaluable part of the
international public health infrastructure. And I never
take for granted all the efforts that you and the other
editors put in to make this a seamless and everyday service."

Damien

Nature: Superspreading and the effect of individual variation on disease emergence

New paper here by Lloyd-Smith et al. on the effect of individual variation in infectiousness. I haven't read it yet, but by the abstract it looks very interesting.

From the editor's summary:

From Typhoid Mary to SARS, it has long been known that some people spread disease more than others. But for diseases transmitted via casual contact, contagiousness arises from a plethora of social and physiological factors, so epidemiologists have tended to rely on population averages to assess a disease's potential to spread. A new analysis of outbreak data shows that individual differences in infectiousness exert powerful influences on the epidemiology of ten deadly diseases.

Damien

Thursday, November 17, 2005

Weekly Standard: Fuss and Feathers

Interesting and informative article here by Michael Fumento.  He addresses some of the hyperbole in the media.

Here's a snippet from the end of the article:

Bottom line? We are all going to die. But from various causes. There probably will be another pandemic, but nobody knows when or what its origin will be. We do know that with every month that passes, we'll be better prepared. Unless the current panic, having failed to materialize, makes us overly complacent. That's a real possibility. In 1976, swine flu went from "next pandemic" to laugh line on Saturday Night Live in record time. And as for those anointed experts, public health officials, and reporters whose wall calendars always read "1918"--it's time to buy a new one.

Damien

WCS: Urge Congress to Establish an Early Warning System for Avian Influenza that Includes Wild Bird Surveillance

The Wildlife Conservation Society has a campaign to support the development of a global network for wild bird disease surveillance, including avian influenzas.  People can follow this link to a site where, with one click you can send correspondence to US Federal government representatives in support of developing such a network.

I really believe that we need to be looking at wild bird health, and wildlife health in general, to protect human health.  When over 60% of the 1400 human pathogens can transmit among humans and animals (e.g., are zoonotic), and over 75% of emerging infectious diseases zoonotic in origin (reference), we can little afford to ignore animal diseases.  This program would provide an early warning system for new pathogens, such as avian influenza.

Damien

Wednesday, November 16, 2005

Why is it taking so long to figure out which AI subtypes were in the Canadian samples?

A story from the Canadian press here.

Here is a snippet:

Teasing out flu viruses found in ducks taking longer than expected: officials

Helen Branswell, CP

TORONTO (CP) - It's proving harder than anticipated to type the avian flu viruses wild ducks sampled in Canada were carrying because a number were co-infected with several strains, creating a viral "soup" that is difficult to separate down to its basic ingredients, government officials have admitted.

They say, however, that it appears that none of the viruses are highly pathogenic, a finding that would support the suggestion none of the birds were carrying the worrisome Asian H5N1 flu virus, which is a so-called high path virus.


Damien

Tuesday, November 15, 2005

Taiwan CDC: no birds have tested positive for H5N1 in Taiwan.

From a press release (or at least I think that's what this is...)

CDC INSISTS NO TAIWAN BIRDS INFECTED WITH H5N1

2005-11-15 23:22:03

Taipei, Nov. 15 (CNA) No bird in Taiwan has so far tested positive for H5N1, the most virulent strain of avian flu, the Center for Disease Control (CDC) under the Department of Health said Tuesday.

I noted this previously, but will reiterate.  The birds from Taiwan must have contacted other, infected birds en route at some point.  Who knows where those birds are now?

Damien

How does high pathogenicity evolve in avian influenzas?

Here's my hypothesis, for what it's worth....

In its simplest terms, evolution works by two processes. First, mutation and reassortment provide genetic variation. Second, selection favours the sets of genetic material that are most fit (i.e., will leave more progeny than other sets of genetic material). These processes work with all living things, whether they are influenza viruses or humans.

With respect to influenzas, wild birds of various species are the reservoir for all avian influenzas. However, these viruses tend to be of low pathogenicity (LPAI), causing only mild transient illnesses. Until this year, science had described only one outbreak of a high pathogenic avian influenza (HPAI) in wild birds in the absence of affected poultry populations - an outbreak of HPAI in common terns in South Africa in the 1960s. Since its emergence in 1996, H5N1 had been isolated from a few wild birds that clearly obtained the virus from nearby infected domestic bird populations. However, these were local spill-over events, and the virus was not sustained.

So how do you get HPAI in poultry from LPAI in wild birds. My hypothesis, and I don't claim that this is original, when HPAI strains appear through mutation and/or reassortment, the conditions do not favour the HPAI strains over endemic LPAI strains (see figure below). In contrast, in the wildlife and poultry trade, the high turnover of susceptibles, poor sanitary conditions, and high stress fuel the fire, so to speak, and HPAI strains become dominant through natural selection. This is why HPAI H5N1 first appeared in the markets of southern China.

However, something has changed this year. HPAI H5N1 seems to be persisting in wild bird populations, at least long enough to get to Mongolia and perhaps to Eastern Europe. Now this is totally speculation, but perhaps the evolutionary landscape for influenza is such that HPAI is unlikely to evolve in wild birds, but now that it has evolved in poultry and domestic waterfowl, it is capable of persisting in wild birds. It remains to be seen how long it will persist.


UK DEFRA: An epidiomological report on avian influenza in a quarantine premises in Essex

The UK Department of the Environment, Food and Rural Affairs has released a report on the H5N1 discovered in quarantine in the UK. The PDF can be accessed here. It seems the parrot from Surinam was likely not H5N1 positive: samples from the parrot were pooled with the Taiwanese birds (pooling samples is standard procedure), and so when the pool was positive, they could not determine which of the birds actually had the virus.

Here are the conclusions from the report:

• The parrot and budgerigar kept as pets by the keeper at the adjoining premises were not infected with an AI virus.
• No isolates of avian influenza virus were made from the birds imported from Surinam or the sentinel chickens other than the initial pooled sample, which included a mesia.
• Within the species imported from Taiwan the virus (H5N1) was only detected in the Mesias.
• H5N1 virus was only isolated from a proportion of the stored dead birds. Autolysis may have precluded virus isolation from some of these birds.
• No virus was isolated from the healthy Mesias that were humanely put down on 21 October. This suggests that mortality in this species was associated with H5N1 infection, but it is uncertain whether it was the only cause of death
• H5N1 infection was, on the balance of probabilities, introduced into the facility by the Mesias
• Infection with H5N1 was transmitting between the Mesias, but from the evidence of the virological examinations it had not transmitted to the other species in the facility.
• The molecular genetic characterization isolate of H5N1 examined so far has indicated that it is most closely associated with an isolate from Chinese ducks.
• The mortality in the Surinamese Caiques does not appear to be associated with H5N1 infection – the bird that was dead on arrival was virus negative.

Damien

Monday, November 14, 2005

H7N3 in a Taiwanese "migratory bird"

From Reuters:

TAIPEI, Nov 14 (Reuters) - Taiwan found a highly pathogenic strain of avian flu, H7N3, in droppings left by a migratory bird and is carrying out tests to see if the virus has spread to nearby poultry farms, the agriculture department said on Monday. Like the deadly H5N1 strain of bird flu, which has killed more than 60 people around Asia, the H7N3 strain can infect humans, said an official at the Council of Agriculture.

From AFX:

'It is not sure if the strain is a virulent or less virulent form,' Huang Kuo-ching, a bureau section chief, told Agence france-Presse, adding that no dead birds have been found in the area.


Finding H7N3 in a "migratory bird" (what species?!) is not particularly surprising - avian influenzas are quite common in migratory birds. It would be unusual if this is a highly pathogenic strain of H7N3, as high path avian influenzas have been rarely isolated from wild birds (summary of 04/05 isolations in this ProMED post). Aside from an outbreak in South Africa in common terns in the early 1960s, 2005 was the first year where significant numbers of wild birds were affected by high pathogenic avian influenza in the absence of nearby infected poultry populations (i.e., the Mongolia outbreak and possibly the QInghai outbreak).

As with the low path H5N1 in Italy, this strain could turn out to be low path H7N3.

For info on the high path H7N3 outbreak in British Columbia in 2004, click here.

Damien

Sunday, November 13, 2005

CDC EID: Host Range and Emerging and Reemerging Pathogens

An update of a previous review of factors associated with emergence of diseases is in upcoming issue of the CDC journal Emerging Infectious Diseases.  Here's the abstract

Host Range and Emerging and Reemerging Pathogens

Mark E.J. Woolhouse* and Sonya Gowtage-Sequeria*
*Centre for Infectious Diseases, University of Edinburgh, Edinburgh, United Kingdom

An updated literature survey identified 1,407 recognized species of human pathogen, 58% of which are zoonotic. Of the total, 177 are regarded as emerging or reemerging. Zoonotic pathogens are twice as likely to be in this category as are nonzoonotic pathogens. Emerging and reemerging pathogens have not been strongly associated with particular types of nonhuman hosts, but they are most likely to have the broadest host ranges. Emerging and reemerging zoonoses are associated with a wide range of drivers, but changes in land use and agriculture are most commonly cited. However, although zoonotic pathogens do represent the most likely source of emerging and reemerging infectious disease, only a small minority have proved capable of causing major epidemics in the human population.


Damien

ProMED: Italian H5N1 confirmed as LPAI

From ProMED:

Date: Sat, 12 Nov 2005
From: Communications Office, Istituto Zooprofilattico Sperimentale
delle Venezie (IZSVe) <comunicazione@izsvenezie.it>


Report on the H5N1 Low Pathogenic Avian Influenza (LPAI) Isolate in
Italy - November 2005
--------------------------------------------------
On 8 Nov 2005, a type A influenza virus isolate was submitted to the
National Reference Laboratory for Avian Influenza in Legnaro (Padova,
Italy) for detailed characterization. The virus was isolated from a
cloacal swab collected from a wild duck hunted in an area located in
the municipality of Mirandola, province of Modena, in Emilia-Romagna
Region.[Lat: 4:53:16N (44.8878), Lon: 11:04:03E (11.0674), about 45
km north of the city Modena].

On 9 Nov 2005, the isolate was typed as a Low Pathogenic H5N1 by
haemagglutination inhibition test, neuraminidase inhibition test, and
genetic analysis.

The amino acids sequence deduced from the cleavage site of the
haemagglutinin molecule (PQRETRG) is typical of low pathogenicity
avian influenza viruses (LPAI). Therefore it is a completely
different pathotype than the Asiatic highly pathogenic (HPAI) H5N1
viruses.

The Italian H5N1 represents a different virus, not related
genetically to the aggressive Asiatic H5N1. This has been
demonstrated by the analysis of the HA gene. The preliminary results
indicate that the Italian virus is genetically related to other LPAI
viruses commonly isolated in wild birds in Europe. The HA gene of the
isolate correlated with the following LPAI strains sequences
deposited in international databases: A/mallard/NL/3/99(H5N2);
A/mallard/Sweden/7/02(H5N2); A/mallard/DK/64650/03(H5N7).

More than 1000 samples collected from wild waterfowl in Italy have
previously been tested with negative results for H5N1 HPAI.

--
Dr. Romano Marabelli
General director
Directorate General for Veterinary Health and Food
Ministry of Health, Rome - Italy

This report illustrates that while all pathogenic strains of avian influenza found to date have been either H5 or H7, not all H5 or H7 strains are pathogenic.

Once again, the species involved was not reported. "Wild duck" is not informative!

Modification: the "wild duck" was a mallard (ProMED)

Damien

Saturday, November 12, 2005

What's in a name?

"Wild bird flu" vs. "Poultry flu" ...

There seems to be (at least a small) battle over the moniker for the current highly pathogenic avian influenza A(H5N1) strain circulating in Eurasia. Henry Niman over at Recombinombics prefers the former, while the folks over at Birds Korea prefer the latter.

It probably doesn't matter what we call it (the virus certainly doesn't care), but I find it interesting that there seems to be an overtone of blame associated with each name. For Dr. Niman, wild birds are apparently going to take this global and seed the pandemic that will kill us all, while for Birds Korea, it is poultry that is the culprit.

I admit that the greatest risk to humans (albeit a very small one at this point) of becoming infected with HPAI H5N1 is contact with infected poultry - there are just so many more infected domestic ducks and chickens than free-ranging waterfowl at this point, and humans generally do not come into close contact with wild birds in the same way they do their domestic ducks. Furthermore, until this year, most of the spread of HPAI H5N1 has been through movement of domestic birds.

That been said, I think it's important to avoid blaming one group or another. We should identify the risk factors and take steps to mitigate them - "blaming" this or that implies that there is intent, and consequently this or that must be "bad". As far as we can tell, it's the same virus (granted continually changing) in both wild and domestic birds. This is a classic "spillover/spillback" of a disease between domestic animals and wildlife.

Furthermore, as there are 140 odd possible subtypes of avian influenza, the monikers "wild bird flu" or "poultry flu" are vague at best and misleading at worst.

Personally, I think we should stick to using the precise, if not cumbersome, "highly pathogenic avian influenza A(H5N1)", or even the shorter HPAI H5N1.

Helen Branswell also comments here.

Damien

For students interested in wildlife epidemiology

The University of Calgary is opening a new veterinary school, with a "population medicine" stream:

  • Population Medicine: Public Health, Eco-Health and Zoological Medicine: This stream will focus on veterinary practice and research as it relates to wildlife conservation and management. Graduates of this program will enter veterinary practice in wildlife management organizations, zoos, or related research institutions.
I'm not saying that you have to go to vet school to have a career in wildlife diseases (I sure didn't!), but this program does seem pretty exciting.

Damien

Some links to wildlife disease sites

The whole bird flu situation is bringing the whole wildlife disease issue to the forefront of people's minds.  I thought I would provide a few links to some good sites with wildlife disease information in case people were interested in other diseases. 

Most provincial and state wildlife agencies have wildlife disease web pages as well.  If people have suggestions for links, I'd be happy to add them here.

Damien

Global surveillance for avian influenza wild birds?

Rob Fergus over at "The Birdchaser" posted a story about a plan by Senator Lieberman to create a global network for avian influenza surveillance in wild birds.
 
With about $10 million slated for wild bird surveillance out of $8 billion targetted for pandemic influenza preparedness in the Harkin-Specter amendment, this is a cost-effective way to counter this threat upstream before a global pandemic.  Surveillance in wild birds will provide an early warning system for viral changes, provide new strains for vaccine production,  help mitigate risk of new outbreaks, and generally improve our understanding of the epidemiology of avian influenzas.

If this gets through committee, I hope the plan includes surveillance of birds in the wildlife trade as well.

Damien

No word on neuraminidase subtype for CDN H5 influenzas from wild birds

This article from the Vancouver Sun is mainly about the pathology of H5N1 and SARS in humans, but there is one line indicating that the results from tests for the neuraminidase subtype for the H5 positive birds in Canada (previous comments here, here, and here) are yet to come:

Meanwhile, the Canadian Food Inspection Agency said Thursday it is still not known what type of bird flu strain has infected wild migratory ducks in Quebec and Manitoba. Preliminary results found the birds were infected with the H5 subtype. Officials are still awaiting tests to determine the "N" type of the virus.

I don't agree with the abundant conspiracy theories (e.g., on this curevents thread) about why the results haven't been yet released. I think they really don't have them yet.

I've heard rumours that many of the sampled birds had multiple infections with several strains of influenza, as might be expected. I am not a virologist and so my understanding of the technical aspects of this is limited, but I understand the testing is done by identifying the "H" subtype and the "N" subtype independently, so perhaps it is taking a while to figure out which "H" goes with which "N".

This is just a supposition however. I do think the rapidity and openness with which the Canadian Food Inspection Agency (CFIA) released information on finding H5 is really good evidence that there is no conspiracy. If the CFIA really wanted to hide something, why would they publicly announce the discovery of the H5?

Damien

Friday, November 11, 2005

CBC: Kuwait confirms flamingo had H5N1 virus

The CBC is reporting today that the flamingo found on a Kuwaiti beach had H5N1, while the peacock in quarantine had H5N2, in contrast to yesterday's report. No word if the flamingo had a high or low path H5N1. I suspect it was high path ... why else would they test it if weren't sick?

Damien

Thursday, November 10, 2005

New findings: Kuwait and Italy

Two new reports today of findings of H5 influenzas, both apparently of low pathogenicity.

First Kuwait:

Sheikh Fahd Salem Al-Ali Al-Sabah, the head of agriculture and fisheries in Kuwait, said the first case was discovered in a peacock held in quarantine at the airport. The bird had been imported from Asia, but Mr Al-Sabah did not specify the country it came from.
The second case was a migratory flamingo that had been found on a beach.

"Immediate action was taken and the situation is under control," said Mr Al-Sabah. "All of our national production of poultry and eggs are free of the disease."

No cases of bird flu among humans have been reported in Kuwait.

Another official from the same authority said laboratory tests on the birds identified the flu strain as H5, but it was not the deadly N1 variety.

"The strain was H5N2 which is less harmful than H5N1," he said. "We are satisfied with our tests, and we find no need for further investigations."

Next Italy:

Italy has found a form of the H5N1 virus in a wild duck, but the Health Ministry said on Thursday it was not dangerous and bore no relation to the strain of Asian avian influenza that has killed more than 60 people.

The H5N1 virus was identified on Wednesday in a testing center in northern Italy, the health ministry said. It added the virus was genetically similar to strains frequently found among wild waterfowl in Europe, and not highly pathogenic.

"There is no alarm. There is no new concern," ministry official Elisabetta Alberti Casellati said.

"The case of H5N1 identified yesterday ... has nothing to do with the cases of Avian influenza registered in Asian countries, because it deals with a low pathogenic strain."

The virus was found in only one bird in the more than a thousand tested so far, the ministry said.


On a related topic, here is a great article by Helen Branswell that explains some of the terminology of avian influenza.


Damien

Monday, November 07, 2005

Conservation International: New Study Uncovers Major Inaccuracies In Global Wildlife Trade Monitoring

Text of the press release here.

I guess I agree that it is important to have good records of the legal wildlife trade. However, it's the illegal trade, that dwarves the legal trade in volume and money, that is the real problem from a health perspective. It's the illegal trade for which we have no good numbers.

Damien

Thursday, November 03, 2005

WCS press release: Avian flu vaccine under development with help of WCS

I've often argued here the importance of studying disease issues at the wildlife/livestock/human interface.  We just can't ignore livestock and wildlife health if we really want to protect human health as over 60% of the 1400 known human pathogens and and ~75% of emerging infectious diseases  transmit between people and animals.

A new press release from the Wildlife Conservation Society outlines how the virus samples they collected during their expedition to Mongolia will be used in part of a human pandemic influenza vaccine. 

I still think it's more important, and cost-effective, to stop avian flu before it becomes a pandemic, through improved biosecurity to reduce transmission: 1) within and among poultry and domestic duck production facilities, and 2) between domestic and wild birds.  This is currently largely a domestic bird disease, and the best way to stop its spread (and therefore reduce opportunities for it to evolve the ability to transmit among humans) is in domestic birds.

However, if we are unable to stop it from going pandemic, having the best vaccine possible to protect humans is critical.  The work to obtain samples of the H5N1 virus from Mongolia by WCS will help in this endeavour. 



New book: Conservation and Development Interventions at the Wildlife/Livestock Interface

A new book is out on the relationships between wildlife, livestock and human health, particularly with respect to economic growth in the developing world. Published by the World Conservation Union, it is available for free download here (links to PDFs way at the bottom).

Damien

Two US Government plans to contain bird flu

Finally, we have the answer to bird flu.  Here are two brilliant plans to protect us all ...

The Borowitz Report: U.S. PLANS TO MAKE BIRDS OBESE - Would Slow the Spread of Avian Flu, President Asserts

and

The Onion: Bush Orders Mass Bald Eagle Slaughter To Stop Spread Of Bird Flu


Damien

CDC: Bushmeat hunting and deforestation in prediction of zoonoses emergence

Interesting review of disease emergence and bushmeat coming up in Emerging Infectious Diseases.

Bushmeat Hunting and Deforestation in Prediction of Zoonoses Emergence

Nathan D. Wolfe, Peter Daszak, A. Marm Kilpatrick, and Donald S. Burke*

Abstract:
Understanding the emergence of new zoonotic agents requires knowledge of pathogen biodiversity in wildlife, human-wildlife interactions, anthropogenic pressures on wildlife populations, and changes in society and human behavior. We discuss an interdisciplinary approach combining virology, wildlife biology, disease ecology, and anthropology that enables better understanding of how deforestation and associated hunting leads to the emergence of novel zoonotic pathogens.

Damien

H5N1 and Canada's First Nations

Good commentary on the potential effects of a pandemic flu on aboriginal communities in Canada here.

Damien

Wednesday, November 02, 2005

H5 avian influenza in British Columbia

Not surprisingly, avian influenza of the H5 subtype have been found in "ducks" in British Columbia .  The neuraminidase subtype is currently being determined. 

"I can tell you right off the top, there's no question we were surprised by the large number of H5 samples [25% of 700 samples],'' British Columbia's Chief Veterinarian Dr. Ron Lewis told a teleconference call from Victoria.

"But having said that, we've never tested birds in this flyway before, so we really don't have any idea whether this is a normal factor or whether these are increased numbers or whether they're decreased numbers. It is just a snapshot surveillance at one particular point in time.''

I agree with both statement - in the Central Flyway, H5 is much less common that what was seen in this sample, but as this is the first time the Pacific Flyway has been sampled in British Columbia, it is hard to say what this high percentage means.

I would be very surprised if this strain turns out to be the same H5N1 that is widely distributed in Eurasia. 

Damien

Tuesday, November 01, 2005

More comments on the H5 positive birds from Canada

I believe Henry Niman, who maintains the Recombinomics blog, is overstating the significance of the recent finding of H5 influenza in wild birds in Manitoba and Quebec.  His comments are here, here, and here.

His main point is that H5 subtypes are hardly ever isolated from wild birds in Canada, and cites only 2 deposits in Genbank as evidence for this statement.  Therefore, he argues " ... H5 serotypes in Canada a rare, raising concerns that the 33 H5 isolates are HPAI H5N1."

I disagree with him.  Although rare, low pathogenic H5 avian influenzas have been isolated several times from migratory birds in Canada, forming 2-3% of all isolations of influenza from wild ducks and shorebirds in North America (Webster et al. 1992). 

The Canadian study is not yet complete so we don't know how many samples have been taken and what other serotypes have been found - we just don't have all the information to put these isolations into context yet.  When the study is complete, we may find that the handful of H5 positives reported by the Canadian government is perfectly in line with what would be expected from previous surveys.  Ultimately, determining the neuraminidase (N) subtype, followed by pathogenicity trials to determine if this is high or low pathogenic influenza, is necessary to settle question.

There is nothing to be gained by making alarmist and speculative statements from less than all the data.  The Canadians should be commended for conducting this study and reporting the results in a timely, open manner.  We need more baseline data like these to put the emergence of new viruses in perspective.

Damien