Medical News Blog

Case number changes between Ebola virus disease reports...

Ebola virus, Graphs, outbreaks, reporting, West Africa, WHO

This is one of my favourite charts for following the Ebola virus disease outbreak in West Africa because it shows how things are changing from report to report.

It plots the total number of suspected, probable and laboratory-confirmed cases between reports - which is a measure of change over time that is not cumulative.

That's not to say that understanding this chart is easy for everyone...as with everything, what you take away from it may be heavily influenced by your own perspective and your background in reading graphs. I have written something about how to read some of the graphs on my blog here, which may be helpful too.

Uses World Health Organization data up to and including the Situation Report from the 5th-Sept, 2014.
Click on chart to enlarge.

I've marked up the last three periods between reports to highlight that the time changes differently. You can see this for yourself if you look carefully at the horizontal or "x" axis (the one that has the dates) and look at where each dot lines up with its date. Some are further apart than others.

You can also mouse over the dots on the interactive version of the graph here. That will tell you the dates. THe subtraction is up to you though!

The lines joining the dots here suggest what is happening between the WHO Reports, but the line do not actually use any real collected values...because we don't have them to plot.

Technically, a bar graph would be more accurate, but I find a line graph easier to read at a glance. So do remember - we don't know what is happening between those dots. We're just presuming it.

Editor's Note #20: Tweepidemiology...

Editor's Note, SoMe, Tweepidemiology, Twitter

Updated 05JUL2015

Followers of my @MackayIM Twitter account (and this blog which gets promoted through it) since I started tweeting. It shows the cumulative rise and rise of followers and the relationship of the rate of those rises to very active periods of infectious disease outbreaks and epidemics over the past 18-months or so.
Click on the graph to enlarge

While it's hard to separate whether I pick up followers because of the delivery of specific content or because as you pick up followers, they help spread the word and you pick up more followers, to simple old me this cumulative graph looks like MERS-CoV and the West African Ebola virus disease outbreaks drove people to seek information. Sometimes those people have done me the honour of following me on Twitter, accompanying me on my own journey to understand what's going on. I'm constantly amazed at that, let me assure you.

I thought it worth having a look at the Tweepidemiology of my Twitter account. That is, the epidemiology of my Twitter followers - a bit of a long bow - but you follow me because I talk about infectious disease outbreaks and stuff and because I like my new word...I'm keeping with it!

I paid Twitter Counter to get my Twitter data, plotted it in Excel, tidied it using Illustrator and here it is.

I started Tweeting a little after I started blogging - this Twitter thing is for the young people and their constant need to take selfies and update the world on their lives...live and learn.

Despite VDU blog posts on the emergence of influenza A(H7N9) virus in China dating back further in time, I came to Twitter well after H7N9's Wave 1 was engaged. So the slow burn could have been due to that or just because no-one knew me or that I could generally be trusted and generally don't spout drivel.

Generally.

So there ya go - Tweepidemiology - a way of looking at when and perhaps why one gains followers through social media when it's used to engage the public and try and help people understand what's happening with new or emerging viruses and diseases . Perhaps I should check what happens when I post photos of my cat too.

Updates...

Corrected some typos and grammatical errors

Ebola: Blood, sweat and tears...

acquisition, Ebola virus, risks, Saliva, Sweat, Tears, transmission, West Africa, Zaire ebolavirus

This post follows up the recent one on convalescent semen being able to harbour infectious Ebola virus (EBOV; although I am not aware of any infection resulting from this route of transmission there has been at least one report for Marburg virus [4]).

I thought I'd give the same treatment to tears and sweat which are also fluids intermittently listed as possible sources of EBOV infection for humans. Some examples of the scientific literature which support the risk messaging, follow.

Blood...

I think we are all pretty clear that the blood of an advanced case of Ebola virus disease (EVD) is heavily laden with virus and is the most serious of the risk factors for acquiring infection by an ebolavirus.

Viral loads (amount of virus in the sample) in blood can be above 10⁶-10⁸ plaque forming units or copies (pfu; a measure of infectious virus present using a lab test that measure the impact of virus on infected cells; copies measure viral genome and cannot prove infectious virus is present) per millilitre of blood in acute phase disease patients and non-human primates.[5,6]

Sweat...

There is not a lot on sweat containing signs of an ebolavirus.

Bausch and colleagues found no trace of EBOV in a single acute sweat sample.[1]
Jaax and colleagues found that in experimentally infected non-human primates (NHPs; rhesus macaques), that connective tissues next to hair follicles and sweat glands in the skin as well as the cells lining ducts of glands in the skin were sometimes positive for EBOV antigens (proteins).[2]
Davis and colleagues infected NHPs (African green monkeys) and found signs of EBOV antigens in the cells lining the sweat gland ducts and in cells in the connective tissues next to hair follicles, but no virus particles by electron microscopy.[3]
Zaki and colleagues found heavy signs of EBOV antigens (proteins) in the tissues around the sweat glands, but rarely also within sweat glands and ducts.[8] No virus particles were seen in the sweat glands or ducts when examined by electron microscopy.

Tears...

There is also very little I have found on this one.

Bausch and colleagues found EBOV RNA in tears from 1 sample, but no infectious virus could be isolated.[1]
Jaax and colleagues found some signs of virus in macrophages in the ciliary body of the eye of experimentally infected NHPs

Spit...

Bausch and colleagues found infectious EBOV in 1 of 12 acute saliva samples (from 10 patients; none from 4 convalescent samples) and EBOV RNA in 8 of 12 (67%) of acute samples (none from convalescent samples).[1] RT-PCR positivity was significantly associated with fatal outcome.
Formenty and colleagues found EBOV antigens and EBOV RNA in oral fluids from fatal cases and those who survived infection.[7]

References...

The fifth I give you...[UPDATED]

Ebola virus, EVD, Guinea, Liberia, Nigeria, Senegal, Sierra Leone, West Africa, Zaire ebolavirus

Senegal.
According to it's Minister of Health, Awa Marie Coll Seck[1,2], a case of Ebola virus disease (EVD) has been imported from Guinea and it is confirmed by testing at the World Health Organization's collaboration Centre, the Pasteur Institute in Dakar.

Interesting that this occurred one week after Senegal closed its borders (again) with Guinea.[3,4] The infected 21-year old Guinean student travelled on 21-August to Dakar. On the 23rd he presented to a hospital but did not admit to being in contact with known EVD cases; Guinea issued an alert that a person with EVD contact has escaped surveillance 27-Aug; Senegal closed its borders around 22-August.[5,6,7,8].
[WHO Disease Outbreak News places his movements ahead of the closure of the border, arriving in Senegal 20-Aug [8]]

These borders are leaky and so the effect of "closure" essentially hinders aid, trade and economy (all very important to the region, especially right now) but ~~very clearly~~ ~~does~~ may not stop the spread of human hosts~~-as we have seen here~~.

Humans are the variable in outbreaks.

They behave differently each time.

They respond differently each time.

This is why no two outbreaks are identical.

It's why you're a mug to assume this outbreak will be like the last outbreak.

While it looks like this is now a case study in why closing a border is ineffective, I maintain a position that border closures can't contain infectious disease. And please, do not point me to "temperature measurement" as a way to ensure capture of infected individuals. You could easily be harbouring an infection that does not yet express the symptom of fever.

Click on image to enlarge.
Graphic lifted from a great CNN video narrated by
Dr Sanjay Gupta. The video describes an example of
contact tracing and its importance to the fight
to contain EVD.[2]

The contact tracing starts in Senegal now. A 42-day clock starts for the country and a signs and symptoms watch continues on all this case's contacts for 21-days.

References...

MERS-CoV around the house-yes, it does transmit at home

contacts, household, MERS, MERS-CoV, seroprevalence

Click on graph to enlarge.

Some Middle East respiratory syndrome coronavirus (MERS-CoV) questions remain stubbornly unanswered even after two and a half years.

Today comes a study from Prof Christian Drosten and colleagues, including Prof Ziad Memish, released by the New England Journal of Medicine.[1] This study takes a look at MERS-CoV infection among the contacts of MERS cases.

We already know that asymptomatic or "silent" MERS-CoV infections are not rare. At least 17% of detections of this virus have occurred in people with no overt signs or reported symptoms of disease. That's not to say that they didn't have a slightly raised temperature, headache, sniffle or something very mild that got overlooked or forgotten, but nothing noted or noteworthy. I'd love to see a study on asymptomatic MERS-CoV infected people that looked into fine detail signs and symptoms by the way-that might tell a nice little story about "silent" infections.

This new study looks at the contacts of infected cases from 26 different households, each with a single confirmed MERS-CoV infected case, with MERS. These households provided throat swabs from 280 contacts and antibody test results on at least 1 sample (only 44 permitted a second voluntary blood sample be taken-a shame) from the 280 contacts as well.

Some interesting findings included:

Median age of cases (65.4% male) was 55-years
Median age of contacts (52% male) was 29-years
Cases 7 household contacts (2.5%) were viral RNA-positive (RT-PCR) within 2-weeks of the index patient's illness onset. Similar to what PCR-based studies conducted previously have yielded.
5 household contacts (1.7%) were considered antibody positive after a series of different tests were used. 3 were positive between 2-3 weeks after the index case's onset, and 1 each before or after that period.
some indication that neutralizing antibodies against MERS-CoV might be low level and short lived in mild or asymptomatic infections and that previous antibody studies may have missed some cases if the took blood too long after a mild infection

Overall, 12 (4%) contacts acquired MERS-CoV infection from an index case, across 6 of 26 households (23.1%).

Among others, one question I'd like answered is whether symptomatic cases being kept in home isolation, which was occurring during the Jeddah-2104 outbreak when they don't need hospital-based supportive care, is the best option for stopping transmission? We don't know whether mild or silent infections can transmit virus, which remains another important question. While 4% seems like a small proportion, it's big enough to perhaps explain some of the sporadic case occurrences. Also, we should be mindful that MERS-CoV infection is associated with the death of a third of the people it infects. I'd want to be pretty sure I wasn't letting a house-bound shedding mild/silent person spread MERS-CoV to a visiting old uncle with a co-morbidity.

References

http://www.nejm.org/doi/full/10.1056/NEJMoa1405858
If this is what MERS-CoV detections look like with more testing...what is the "normal" community level of virus?? [UPDATED]
http://newsmedicalnet.blogspot.com.au/2014/04/if-this-is-what-mers-cov-detections.html
Guidelines for home isolation related to MERS Corona Virus infections | May 2014http://www.moh.gov.sa/en/Documents/3-Isolation.pdf

The battle of Ebola gains a second front...the Democratic Republic of Congo (DRC; formerly Zaire) [UPDATE #3]

Democratic Republic of the Congo, Ebola virus, Hammer-headed bat, Hypsignathus monstrosus, Sudan ebolavirus, West Africa, Zaire ebolavirus

So there are three reasons for this post.

It may be a little while before we get solid confirmed information from the DRC and I think maps are useful for those of us who are ignorant of where countries live! [See below for update from WHO]
I'm looking for a quick post so I can move the previous post's grisly pictures down the page!
Mike Reid (see comments below; many thanks) brought to my attention that the range of the hammer-headed bat (Hypsignathus monstrosus; [5]) overlays the current ebolavirus outbreak areas strikingly well. I lifted that range graphic and (imperfectly, in pink) overlaid it onto my map - et voila!

Data for the hammer head bat's (Hypsignathus monstrosus) range come from The International Union for Conservation of Nature (IUCN) Red List of Threatened Species. I adapted the graphic for VDU from Wikipedia [3]

An 24-Aug report quoted the Minster for Heath, Felix Kabange Numbi.[2] This latest outbreak occurs in a country that was the site of the first (known) outbreak of a virus of species Zaire ebolavirus (called Ebola virus [1] or EBOV), and which has had six other battles with Ebola virus disease (EVD).

One of the two viruses was reported to have been genotyped as a member of the species Sudan ebolavirus (SUDV) and the second was a "mixed" infection of SUDV and an EBOV.[2] A mixed natural infection of a human would be very...unheard of. Can't really say much more though, until we get this all clarified.

A 26-Aug WHO-AFRO update noted that the index case, a woman from Ikanamongo village, died 11-Aug sometime after butchering a bush animal.[6] 24 suspected cases of haemorrhagic fever occurred between 28-Jul and 18-Aug.

The latest updates define that the outbreak is solely due to viruses from the species Zaire ebolavirus.[7,8,9] The EBOV viral variants share 99% nucleotide identity with the Kikwit lineage of viruses from this same species (not "strain"). Put simply, this is the evidence needed to be able to state that the two concurrent EVD outbreaks (indicated in the map above as distinct events), are indeed due to genetically distinct viral variants of Zaire ebolavirus and are not related outbreaks.

For more on naming ebolaviruses - check out my earlier post "Behind the naming of ebolaviruses".[10]

This latest outbreak was previously and relatively quickly (too quickly? Perhaps a message in there for all of us) described by the World Health Organization as being due to gastroenteritis with haemorrhaging...

.@Fla_Medic It is febrile gastroenteritis with haemorrhaging. If i can find the notice, I will posting. DRC is definitely not #Ebola. Best
� Gregory H�rtl (@HaertlG) August 21, 2014

SitRep on #DRC and febrile gastroenteritis with haemorrhaging is only available in French. I can send by email if u ask me. It is not #Ebola
� Gregory H�rtl (@HaertlG) August 21, 2014

...but subsequently we learn today that...

.@Potrblog @WHO I was given premature information from the field. National lab has now tested + for #Ebola. Will be confirmed in a 2nd lab.
� Gregory H�rtl (@HaertlG) August 24, 2014

The outbreaks share at least one common potential animal vector range. This is one of three bat species often pointed to as a possible natural host for ebolaviruses.

Since this is not the first time concurrent outbreaks of ebolaviruses have occurred, I was wondering about seasonal factors and whether they attract or affect bats. This new information adds another piece of of the puzzle.

References

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