VDU's blog: Brazil

Showing posts with label Brazil. Show all posts

Saturday, 20 August 2016

Tests and temps...

From [10]

It's been about 5 weeks since Brazil updated its microcephaly-related-to-Zika-virus reporting index page.

The last post listed (a couple of others made their way out via other channels) was from epidemiological week (EW) No. 26.

For comparison, Colombia is about to post data for EW No. 32. [12]

Interestingly, Colombia's National Institute of Health has not seen any new laboratory confirmed Zika virus disease cases during that same period - so perhaps Brazil is not seeing any either?

Temperature graphs (in Celsius) from
accuweather.com.
Top-Miami Beach, Florida.
Bottom-Rio de Janeiro, Brazil

Meanwhile, more of the US state of Florida is seeing local Zika virus spread.[4,5,6] If we look at the temperature graphs we can see that Miami Beach (around 32'C) is certainly a lot warmer and holding more steady than Rio (around 24'C) in August 2916.

High and fluctuating temperatures are important for flavivirus multiplication in mosquitoes but for the mosquitoes themselves, particularly Aedes aegypti, they can live for about the same period (around 3 weeks) when conditions suit, whether at 26'C or 30'C.[12,13]

As I was recently taught by Rebbeca C Christofferson and Anthony Willson, viral loads do better in mosquitoes living at an optimal temperature. But when more Dengue virus for example, is replicating throughout the mosquito, that can have an effect on the length of their lives, even if not having an immediate impact on mortality.[14]

When you stop and think about it there is a lot going on for a mosquito when it takes a big blood meal.

There could be a huge rapid weight gain, and there can be a 20'C temperature difference between the host's blood and the insect's temperature - that's a big shock at any size! There is also a big osmotic imbalance (difference in osmotic pressure due to the concentration of dissolved solids in the host's blood versus that in the insect's hemolymph [8,9]) and there's a need to get rid of toxic metabolites.[1]

Have you seen that big drop of excreted fluid attached to some species of mosquito's butt? It appears once feeding has started and is something they excrete (urine and concentrated red blood cells; a process called prediuresis) to help them balance osmolarity, offset weight gain and sometimes to regulate their temperature through evaporation.[2,7]

Some mosquito species retain the drop ('drop-keeping') making use of evaporative cooling, some emit new drops.[7] As far as I can tell so far, Aedes species don't make use of the drop for cooling. Male mosquitoes don't heat up because they don't feed on blood so they rely on environmental temperatures for heating and cooling.[7]

So much more reading to be done (apologies for errors above - I'm still learning about mozzies) - just not of data from Brazil.

References...

Tuesday, 5 July 2016

Brazil's microcephaly and CNS disorder (M&CD) monitoring: Report No. 32, 2016-Week No. 25...

These graphs are made by me using data obtained from epidemiological week (EW) number 25's Brazil Ministry of Health microcephaly and foetal and infant microcephaly and central nervous system (CNS) disorders (M&CD) report.[1]

Brazil last reported a total of 120,161 suspected Zika virus detections some weeks back. Around one thousand of these have been confirmed.[2,3]

Suspected M&CD cases...

The total number of suspected M&CD cases increased by 126 to 8,165 this EW (compared to last).

The graph above shows the number of suspected M&CD diagnoses in Brazil up to 25-June-2016. The cumulative curve (yellow dots; left hand axis) is growing, but slowly.

This was another weekly rise (orange bars; right-hand axis). These bars are based on the difference in total suspected cases reported this EW compared to that reported in the last EW. This method may not reflect the diagnoses that occurred during the past EW (some may have come from days or weeks earlier), but that level of detail is not available in the MOH report.

Confirmed and discarded M&CD diagnoses...

M&CD cases under investigation increased by 54 to 3,061 this week.

In the graph above, we can see that 50 (blue bars; right hand axis) suspected M&CD diagnoses were discarded upon closer investigation with a current total of 3,466 removed.

The rate of these resolved diagnoses (line with blue dots, left-hand axis) seems similar to the rate of the smaller overall number of confirmed M&CD diagnoses (red dots, left-hand axis).

As of this EW, 20% of suspected M&CD diagnoses have been confirmed while 42% of suspected diagnoses have been discarded-a percentage that has been steady for 4 EWs.

The cumulative number of confirmed M&CD diagnoses does continue its climb this EW, growing by 22 new diagnoses (red bars; right-hand axis) to total 1,638.

The number of these M&CD diagnoses to be confirmed with a Zika virus infection also grows (green dots; left-hand axis) by 37 new detection (green bars; right-hand axis) to 270 this EW after rising by 7 the preceding EW.

Those confirmed Zika virus infections represent 16% (an increase for the first time about 11 weeks) of all confirmed M&CD diagnoses and 3% of all suspect diagnoses.

References...

Saturday, 11 June 2016

More microcephaly to come..?

The Brazilian Ministry of Health presented some information around Zika virus (ZIKV), June 10. Specifically some good news about its recent steady decline ahead of the Olympics. Good timing, huh?

Its always good to see some data - it's unclear if these are clinically suspected (most probably) or laboratory confirmed cases (highly unlikely given the numbers being so high and lab capacity being reportedly so low) from this graph, but if we look further down at Figure 2, the Pan American Health Organization data, which lists slightly fewer cases each week that Brazil (PAHO figures may need updating?), does not list any confirmed cases, only "suspected". I assume that means rashy febrile people.

If we add up the weeks listed by the Ministry, there have been 159,914 cases in 2016.

Figure 1. From Brazil Ministry of Health slideset, June 10.
Slides No.12 and No. 13 [1]
Click on image to enlarge.

So, if these are ZIKV and not Dengue virus, Chikungunya virus, an enterovirus or some other acute cause of rash [2], then should we expect to see a new wave microcephaly and central nervous system disorders starting from around July? I've said July because that is about 184 days pr 6 months after the rise starts - 184 being the magic number between when ZIKV was first identified in Brazil (although we are pretty sure it was there much earlier[3]) and when the first 141 microcephaly diagnoses were announced.[4]

Meanwhile, Colombia - the elephant that won't leave the room - reports just 6 ZIKV-linked microcephaly diagnoses despite nearly eight months having passed since they first identified local spread of ZIKV and there already being nearly 5,000 pregnant women confirmed as ZIKV infected.[5]

Brazil reports just 3,598 pregnant women clinically, epidemiologically or laboratory (presumably a much smaller number) confirmed as infected with ZIKV yet its population is a quarter of Brazil's (48 versus 200 million according to 2013 data via Google). It's a strange one that could be explained by ZIKV alone not being the cause of microcephaly or else by those extra years during which ZIKV was in Brazil but not yet Colombia being somehow key to the occurrence of microcephaly.

First we need a little more genome sequencing to understand whether ZIKV was also present in Colombia for longer than dictated by its first laboratory confirmed case report. Perhaps a ZiCRA project is required?[5]

Meanwhile, it would be great if Brazil published its national numbers in a weekly report - along with confirmed numbers. The promise of the "Boletins Epidemiológicos de Dengue, Chikungunya e Zika" has not been realised with only two reports over the past 10 epidemiological weeks and no specific listing of laboratory confirmed numbers.[6]

I can't help but recall that some were very upset at The Kingdom of Saudi Arabia for what was, in hindsight, relatively better epidemiology data for MERS-CoV. Strange why this has not been an issue here. One of the many mysteries of Zikasteria? I have no answer.

References...

Brazil's microcephaly and CNS disorder (M&CD) monitoring: Report No. 29, 2016-Week No. 22...

These graphs are made by me using data obtained from epidemiological week (EW) number 22's Brazil Ministry of Health microcephaly and foetal and infant microcephaly and central nervous system (CNS) disorders (M&CD) report.[1]

Brazil last reported a total of 120,161 suspected Zika virus detections some weeks back. Around one thousand of these have been confirmed.[2,3]

Suspected M&CD cases...

The total number of suspected M&CD cases increased by 107 to 7,830 this EW (compared to last).

The graph above shows the number of suspected M&CD diagnoses in Brazil up to 04-June-2016. The cumulative curve (yellow dots; left hand axis) is growing, but slowly.

This was another weekly rise (orange bars; right-hand axis). These bars are based on the difference in total suspected cases reported this EW compared to that reported in the last EW. This method may not reflect the diagnoses that occurred during the past EW (some may have come from days or weeks earlier), but that level of detail is not available in the MOH report.

Confirmed and discarded M&CD diagnoses...

M&CD cases under investigation decreased by 145 to 3,017 this week - the eleventh consecutive decrease.

In the graph above, we can see that 190 (blue bars; right hand axis) suspected M&CD diagnoses were discarded upon closer investigation with a current total of 3,262 removed.

The rate of these resolved diagnoses (line with blue dots, left-hand axis) continues to outpace the rate of the smaller overall number of confirmed M&CD diagnoses (red dots, left-hand axis).

As of this EW, 20% of suspected M&CD diagnoses have been confirmed while 42% of suspected diagnoses have been discarded-a percentage that has increased for 18 weeks.

The cumulative number of confirmed M&CD diagnoses does continue its climb this EW, growing by 62 new diagnoses (red bars; right-hand axis) to total 1,551.

The number of these M&CD diagnoses to be confirmed with a Zika virus infection also grows (green dots; left-hand axis) by 1 new detection (green bars; right-hand axis) to 224 this EW after rising by 15 the preceding EW.

Those confirmed Zika virus infections represent 14% of all confirmed M&CD diagnoses and 3% of all suspect diagnoses.

References...

Wednesday, 25 May 2016

Brazil's microcephaly and CNS disorder (M&CD) monitoring: Report No. 27, 2016-Week No. 20...

These graphs are made by me using data obtained from epidemiological week (EW) number 20's Brazil Ministry of Health microcephaly and foetal and infant microcephaly and central nervous system (CNS) disorders (M&CD) report.[1]

Brazil last reported a total of 120,161 suspected Zika virus detections some weeks back. Around one thousand of these have been portability confirmed.[2]

Suspected M&CD cases...

The total number of suspected M&CD cases increased by 89 to 7,623 this EW (compared to last).

The graph above shows the number of suspected M&CD diagnoses in Brazil up to 21-May-2016. The cumulative curve (yellow dots; left hand axis) is growing, but slowly.

This was another slower weekly rise (orange bars; right-hand axis). These bars are based on the difference in total suspected cases reported this EW compared to that reported in the last EW. This method may not reflect the diagnoses that occurred during the past EW (some may have come from days or weeks earlier), but that level of detail is not available in the MOH report.

Confirmed and discarded M&CD diagnoses...

M&CD cases under investigation decreased by 75 to 3,257 this week - the ninth consecutive decrease.

In the graph above, we can see that 114 (blue bars; right hand axis) suspected M&CD diagnoses were discarded upon closer investigation with a current total of 2,932 removed.

The rate of these resolved diagnoses (line with blue dots, left-hand axis) continues to outpace the rate of the smaller overall number of confirmed M&CD diagnoses (red dots, left-hand axis).

As of this EW, 19% of suspected M&CD diagnoses have been confirmed while 38% of suspected diagnoses have been discarded-a percentage that has increased for 16 weeks.

The cumulative number of confirmed M&CD diagnoses does continue its climb this EW, growing by 50 new diagnoses (red bars; right-hand axis) to total 1,434.

The number of these M&CD diagnoses to be confirmed with a Zika virus infection also grows (green dots; left-hand axis) by 1 new detection (green bars; right-hand axis) to 208 this EW.

Those confirmed Zika virus infections represent 15% of all confirmed M&CD diagnoses and 3% of all suspect diagnoses.

References...

Monday, 23 May 2016

Brazil's microcephaly and CNS disorder (M&CD) monitoring: Report No. 26, 2016-Week No. 19...

These graphs are made by me using data obtained from epidemiological week (EW) number 19's Brazil Ministry of Health microcephaly and foetal and infant microcephaly and central nervous system (CNS) disorders (M&CD) report.[1]

Brazil last reported a total of 120,161 suspected Zika virus detections some weeks back. Around one thousand of these have been portability confirmed.[2]

Suspected M&CD cases...

The total number of suspected M&CD cases increased by 96 to 7,534 this EW compared to last.

The graph above shows the number of suspected M&CD diagnoses in Brazil up to 14-May-2016. The cumulative curve (yellow dots; left hand axis) is growing, but slowly.

This was another slower weekly rise (orange bars; right-hand axis). These bars are based on the difference in total suspected cases reported this EW compared to that reported in the last EW. This method may not reflect the diagnoses that occurred during the past EW (some may have come from days or weeks earlier), but that level of detail is not available in the MOH report.
Confirmed and discarded M&CD diagnoses...

M&CD cases under investigation decreased by 101 to 3,332 this week - the eighth consecutive decrease. This may be occurring for a range of (guessed) reasons including:

improved capacity to address a large volume of request for clinical classification of suspect diagnoses.
streamlining the confirmation processes
retrospective application of changed head circumference definitions resulting in reductions to the number of the microcephaly diagnoses.
This aspect will not reduce the number of cases with structural brain changes that occur in the absence of a decreased head size - which are reportedly also related to Zika virus and/or other causal influences.
There is time involved in making these diagnoses because of the need for detailed ultrasound and other diagnostic investigations to identify congenital infection outcomes including intracranial calcifications, dilation of cerebral ventricles or posterior fossa changes and other issues.

In the graph above, we can see that 139 (blue bars; right hand axis) suspected M&CD diagnoses were discarded upon closer investigation with a current total of 2,818 removed.

The rate of these resolved diagnoses (line with blue dots, left-hand axis) continues to outpace the rate of the smaller overall number of confirmed M&CD diagnoses (red dots, left-hand axis).

As of this EW, 18% of suspected M&CD diagnoses have been confirmed while 37% of suspected diagnoses have been discarded-a percentage that has increased for 15 weeks.

The cumulative number of confirmed M&CD diagnoses does continue its climb this EW, growing by 58 new diagnoses (red bars; right-hand axis) to total 1,384.

The number of these M&CD diagnoses to be confirmed with a Zika virus infection also grows (green dots; left-hand axis) by 2 new detections (green bars; right-hand axis) to 207 this EW.

Those confirmed Zika virus infections represent 15% of all confirmed M&CD diagnoses and 3% of all suspect diagnoses - but these are not fair comparisons for a range of reasons I won't go on about here.

References...

Sunday, 8 May 2016

Zika, twins and complexity...

The media reported yesterday on a study underway in Sao Paolo, southern Brazil.[1] The study is looking at five pairs of twins so far - each pair includes one with a diagnosis of microcephaly, and one borne completely healthy. There is no detail on whether any less externally obvious Zika virus related central nervous system (CNS) disease has been sought so far.

From the Australian twin registry website.[8]

In the case discussed in the article, the mum of one such set of twins recalled symptoms of a Zika virus-like infection early in her pregnancy.[1] As you can see in the image to the right (and read at the linked website[8]), "twins" is a pretty broad description. It isn't hard to see how even one monozygotic twin (MZ twins develop from an egg fertilized by a single sperm) that one could become infected when another wasn't. This may be informative to the Three Parent Hypothesis.[9]

With around 3 million live births a year (roughly 8,500 live births average per day; 360 an hour [11]), there is likely to be a goodly number of twins when around 1.5% to 3.4% of live births result in twins of some type.[2,3]

I'm clearly no expert in the area of obstetrics, neonatology or congenital central nervous system disorders. But this finding, certainly not the first or only disease/healthy split between twins of this sort,[4,5,6,7] is fascinating.

To me, this finding highlights how rare the microcephaly and CNS disorder outcome seems to be after a suspected Zika virus infection of a mum at some point in her pregnancy. With so many births and just 1,300 M&CD diagnoses, its clearly nothing like as simplistic as "Zika virus infection while pregnant results in microcephaly".

A visualization some of the things that may have to occur for a maternal
Zika virus infection to result in an M&CD diagnosis.
This assumes that a mother's rash/fever/joint pain illness at some
time in her pregnancy prior to delivery, was due to Zika virus and
not one of the many other possible causes of such non-specific illness.
The order of everything in the grey box - which is not an exhaustive
list - is not intended to carry any meaning.
It is to indicate that there seem to be a large range of things
that must occur in a certain order, at a certain time, at a certain
strength or for a certain period of exposure, for the final outcome of
M&CD to occur in a newborn infant, or aborted foetus.
It may be a different mix that results in different Zika virus-related
disorders - or even in M&CD in one infant compared to the next.

What is for sure though, is that sometimes release of preliminary Zika virus disease study data without more detail and discussion, can give the appearance that things are more simple than they are.

The following tweets were a result of listening to Dr Celina Turchi Martelli, of the Brazilian Ministry of Health’s Fundação Oswaldo Cruz Foundation (FIOCRUZ)-Pernambuco, Brazil.[10]

She gave a little insight into two case-control studies she is involved in, while speaking to the Cura Zika symposium hosted by The University of Pittsburgh.[10]

@AndrewALover From aroudn 38min at https://t.co/3w20ZiN6Yp

if you want to get a better sense of it all. Thoughts? pic.twitter.com/3k33UcVjpF
— Ian M Mackay, PhD (@MackayIM) May 5, 2016

Prelim case-control study results
-#Zika infection detected in 12/23 - Odds Ratio 48

-Martelli #Zika pic.twitter.com/SctPplhRHp
— Ian M Mackay, PhD (@MackayIM) May 5, 2016

In response to those, Dr Andrew Lover crunched some numbers and highlighted that those data, when viewed in isolation, suggest that a Zika virus infection alone is almost guaranteed to result in microcephaly.

@MackayIM OR of 48 = 98% probability of MC given ZIKV(+); lower CI of 5.6 = 84.8% probability. Trimesters? DENV or CHIKV co-infection?
— Andrew Lover (@AndrewALover) May 6, 2016

But that is clearly not the case. Remember that total of 1,300 confirmed M&CD diagnoses amidst 8,500 live births a day? It was very probably not the intended meaning of Dr Martelli either.

This all just exemplifies how confusing the Zika virus epidemic can be to the public, how complex finding a cause(s) to the M&CD surge will be and how much time may yet pass before we get anywhere near that goal.

It's all a bit confusing for scientists too!

References...

Saturday, 7 May 2016

Brazil's microcephaly and CNS disorder (M&CD) monitoring: Report No. 24, 2016-Week No. 17...

These graphs are made by me using data obtained from epidemiological week (EW) number 17's Brazil Ministry of Health microcephaly and foetal and infant microcephaly and central nervous system (CNS) disorders (M&CD) report.[1]

Brazil reports a total of 120,161 suspected Zika virus detections this EW.[1] Around one thousand of these have been laboratory confirmed.

Suspected M&CD cases...

The total number of suspected M&CD cases increased by 115 to 7,343 this EW.

The graph above shows the number of suspected M&CD diagnoses in Brazil up to 30-April-2016. The cumulative curve (yellow dots; left hand axis) is growing, but slowly.

This was another slower weekly rise (orange bars; right-hand axis). These bars are based on the difference in total suspected cases reported this EW compared to that reported in the last EW. This method may not reflect the diagnoses that occurred during the past EW (some may have come from days or weeks earlier), but that level of detail is not available in the MOH report.

Confirmed and discarded M&CD diagnoses...

M&CD cases under investigation decreased by 130 to 3,580 this week - the sixth consecutive decrease. This may be occurring for a range of (guessed) reasons including:

improved capacity to address a large volume of request for clinical classification of suspect diagnoses.
streamlining the confirmation processes
retrospective application of changed head circumference definitions resulting in reductions to the number of the microcephaly diagnoses.
This aspect will not reduce the number of cases with structural brain changes that occur in the absence of a decreased head size - which are reportedly also related to Zika virus and/or other causal influences.
There is time involved in making these diagnoses because of the need for detailed ultrasound and other diagnostic investigations to identify congenital infection outcomes including intracranial calcifications, dilation of cerebral ventricles or posterior fossa changes and other issues.

In the graph above, we can see that 172 (blue bars; right hand axis) suspected M&CD diagnoses were discarded upon closer investigation with a current total of 2,492 removed.

The rate of these resolved diagnoses (line with blue dots, left-hand axis) continues to outpace the rate of the smaller overall number of confirmed M&CD diagnoses (red dots, left-hand axis).

As of this EW, 17% of suspected M&CD diagnoses have been confirmed while 34% of suspected diagnoses have been discarded.

The cumulative number of M&CD diagnoses does continue its climb this EW, growing by 73 new diagnoses (red bars; right-hand axis) to total 1,271.

The number of these M&CD diagnoses to be confirmed with a Zika virus infection also grows (green dots; left-hand axis) by 9 new detections to 203 this EW (green bars; right-hand axis). Those confirmed Zika virus infections represent 16% of all confirmed M&CD diagnoses and 3% of all suspect diagnoses - but these are not fair comparisons for a range of reasons I won't go on about here.

References...

http://portalsaude.saude.gov.br/images/pdf/2016/maio/04/coes-microcefalia-informe-epi-24-se17-2016.pdf

Friday, 29 April 2016

Zika virus (ZIKV) disease in Brazil (not just microcephaly) gets its own report...kinda

UPDATE #1: 05MAY2016

I admit I was hoping for more.

Brazil's Ministry of Health announced its first report containing dedicated Zika virus (ZIKV) numbers this week.[1] Not just the 194 detection made among diagnoses of microcephaly and central nervous system disorders,[2] but among the population as a whole.

I was hoping for something like the Colombian data.[3]

We learned that there have been 91,387 probable cases and 3 deaths in Brazil, nationwide, up until the 2nd April 2016 and that autochthonous (local) transmission was first detected in April 2015.[1]

The report itself is a bit hard to translate though.[4] But it states that 31,616 probable cases have been confirmed. [UPDATE#1 PAHOWWHO lists 1,034 confirmed infections-a more believable figure; sad it was not clearly defined here. I infer from this that "confirmed means probable and "probable" means suspected] It does not say whether this is our old friend "clinically confirmed", or if an actual sample was collected and put through an actual test to see that there was any specific trace of ZIKV or its actual antibody produced in response to infection. This report would be greatly helped by a lot of definitions.

Geographically, Most ZIKV probable cases (39%) were in the south-east followed closely by 33% in the north-east, from where the majority of the world's temporally related M&CD diagnoses have been reported. After that there is a big step down to 19% of probable cases in the west, 7% in the north and 2% in the south.

The highest incidence (cases per 100,000 population) occurred in the mid-west (113.4), followed by the north-east (53.5), south-east (41.4) north (36.0) and south (6.1). It would be very interesting to see this breakdown over time to observe whether ZIKV has moved during this reporting period and if so, in what direction, when and at what speed.

From MMWR article.[5]

Overall, Brazil reports an incidence of 44.7 ZIKV cases per 100,000 people. These are only symptomatic people though, and it remains an open question as to whether the Yap Island ~80% asymptomatic rate that is so widely used and quoted,[6] holds in the Americas epidemic. As recent study of travellers who moved to or returned back to the United States after travel to ZIKV-affected countries, found few ZIKV positives except among those with symptoms - and relevant ones at that (Fever, rash, arthralgia, or conjunctivitis).[5]

From PAHO-WHO report.
28APR2016.[7]

We also learned that here had been 802,429 probable cases of Dengue and 140 associated deaths as well as 39,017 cases of Chikungunya and 15 deaths - over the same period. With so many similar diseases around, I continue to boggle at how "clinically confirmed" Zika virus disease can carry much weight at all - no matter how distinctive the rash looks. Just look at the overlap in the latest PAHO-WHO report's graph above. How do you untangle prevalence let alone causality, without more lab testing?

So, with that, I look forward to Colombia's epidemiology report this weekend.

References...

Updates...

Added PAHO-WHO data on actual confirmed ZIKV infections - 1,034 from new reference, [8]
.

Brazil's microcephaly and CNS disorder (M&CD) monitoring: Report No. 23, 2016-Week No. 16...

These graphs are made using data obtained from Week 16's Brazil Ministry of Health microcephaly and foetal and infant microcephaly and central nervous system (CNS) disorders (M&CD) report [1] and media report.[2]

Suspected M&CD cases...

The total number of suspected M&CD cases increased by 78 to 7,228 this week - the smallest rise reported by Brazil to date. This should not be confused with comments in the latest World Health Organization's Zika virus (ZIKV) situation report which states...

"At this stage, based on the evidence available, WHO does not see an overall decline in the outbreak."

That statement refers to current data whereas Brazil's M&CD report #23 is describing events that may have occurred approximately 20 to 40 weeks ago.[3] I picked that range because foetal disorders with preceding ZIKV detection have been reported to occur very rapidly, between 17 and 20 weeks in one case study.[4]

The chart above reports the number of newly suspected M&CD diagnoses in Brazil up to 23-April-2016. The cumulative curve (yellow dots; left hand axis) is steady and growing, but slowly steadily. This was the lowest weekly rise (orange bars; right-hand axis) on record.

Confirmed and discarded M&CD diagnoses...

M&CD cases under investigation decreased by 31 to 3,710 this week - the fifth consecutive decrease.

In the graph above, we can see that 79 (blue bars; right hand axis) suspected M&CD diagnoses were discarded upon closer investigation.The rate of these resolved diagnoses (line with blue dots, left-hand axis) is slowing but still seems to be outpacing the rate of confirmed M&CD diagnoses (red dots, left-hand axis). The cumulative number of M&CD diagnoses does continue its climb this week (+30), but this is the smallest addition of new diagnoses on record (red bars; right-hand axis).

The number of these M&CD diagnoses to be confirmed with a ZIKV infection also grows (green dots; left-hand axis) but by just 2 new detections to 194 this week (green bars; right-hand axis). That's the smallest rise on record. Those confirmed ZIKV infections represent 16% of all confirmed diagnoses and 3% of all suspect M&CD cases - but these are not fair comparisons for a range of reasons I won't go on about here.

Why are M&CD diagnoses slowing...?

It's not precisely known why the numbers of M&CD diagnoses are slowing in Brazil. Whatever their cause(s), the trigger(s) for the anomalies occurred in the past - as far as 9 months or as close as perhaps 20 weeks. One suggestion which ties in with the timing of arbovirus epidemics in Brazil, is the weather and its impact on the mosquito breeding cycle. (Thanks Luis F. B. Correia) Mosquitoes are assumed to be the major vector for transmitting ZIKV, wherever in the world it may be. That's a safe bet as far as we know. Undoubtedly, reporting on mosquito detections is not a priority. Only Mexico has reported infected wild-caught mosquitoes to date.[5] There have been more monkeys identified as ZIKV-infected than mosquitoes![5,6] For now at least.

The rainy season begins in the north-east (where M&CD has mostly been diagnosed) in May. Infections are likely to pick up from then - if we crudely add 6-9 months to May 2015 we get to October-2015 - January-2016.

August saw a rise in microcephaly diagnoses in Pernambuco State in the north-east.[6]

November is when the Brazil ministry declared a link between M&CD and ZIKV.[7]

It all kinda fits.

None of these numbers are precise though because when and where ZIKV was becoming established in Brazil is not known. It is predicted to have been as early as May-December 2013 based on analysis of viral genome sequences to hand,[9] but local transmission was not detected (looked for?) until April/May 2015.[9,10] It may have been there earlier.

Solid data and answers continue to evade trapping. As do ZIKV positive mosquitoes apparently.

References...

Static pages

Saturday, 20 August 2016

Tuesday, 5 July 2016

Saturday, 11 June 2016

Wednesday, 25 May 2016

Monday, 23 May 2016

Sunday, 8 May 2016

Saturday, 7 May 2016

Friday, 29 April 2016