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Zika    Dengue   Chikungunya  Viruses


June 2016.

Zika continues to be big news.  It has been connected with birth defects in South America and now one case of microcephaly in mother who became infected in South America and delivered here in North America.  Over 20,000 cases of microcephaly occurs in America every year.  It is caused by many problems during pregnancy:

 1. Certain infections during pregnancy, such as rubella, toxoplasmosis, or cytomegalovirus

2. Severe malnutrition, meaning a lack of nutrients or not getting enough food

3. Exposure to harmful substances, such as alcohol, certain drugs, or toxic chemicals

4. Interruption of the blood supply to the baby’s brain during development

5. And now Zika.

 All these conditions occur in South America and other developing countries at a higher incidence than here in the States.  The Zika virus is new to South America so many people are being infected.  There are normally no or mild symptoms from the illness. The children who are getting infected are then immune to it and will not have the illness when an adult who gets pregnant.  So they should want their children to get the illness to protect them.  It works like a vaccine to prevent birth defects later in life. There are a lot of cases of microcephaly now from Zika but when the children who are immune grow up, then the number of cases will be extremely rare.  They estimate 1% of pregnant women will have a damaged newborn with Zika but many cases are not reported since there are such mild symptoms.  The damage rate is probably far less.  America will spend big dollars to develop a vaccine since the disease may eventually come here.  (I mentioned before I worry more about Dengue Fever.)  Many people will want the vaccine and especially adults in child bearing years should get it.   (Interesting how many people who are against the MMR will want this vaccine yet we give Rubella vaccine to prevent such problems.)  Before the chicken pox vaccine, we used to have chicken pox parties where the parent would expose their kids to it.  Then get the disease as a child instead of as an adult when it would be more dangerous.

 Some diseases are less dangerous in children than adults and some are more dangerous as kids like Dengue.  You do not hear much about West Nile like we did years ago.  It came to America in 1999 and there are outbreaks in different states in different years.   In Texas the yearly rate of West Nile was 27-260 cases every year from 2001 to 2011.  Then in 2012 there were 1868 reported cases.  There were a lot of susceptible people in the population and more mosquitos with the virus that year.  The next year there were 183 cases. West Nile is dangerous for the elderly although severe disease is only 1%.  Children hardly ever are hospitalized with it.  But I see 20-30 cases of probable West Nile every year but they never get diagnosed since it is mild and require expensive yucky tests for a disease I cannot treat.  I tell parents it is not a bad thing since they are then immune to it and will not get it when older and more deadly.  Also there was a lot on the news about West Nile so doctors were testing more patients for the infection.  There sometimes is an increase in disease because the doctors and population are looking harder for the disease and not an actual increase the number of cases.  The West Nile story sounds similar to Zika situation huh?

 Protect your children from mosquito bites and especially when traveling to South America, Central America, Mexico, and other countries with high numbers of mosquitos.  Not to prevent Zika but to prevent Dengue, malaria, and other worse diseases. 

 Here is a not-so-complete list of diseases from Mosquitos.

 Banna Fever

Bunyamwera fever

Bwamba Fever


Dengue fever,

Eastern Equine Encephalitis

Jamestown Canyon fever

Japanese encephalitis

La Cross encephalitis


Mayaro virus disease

Pogosta disease

Rift Valley Fever,

Ross River fever

Saint Louis encephalitis

sleeping sickness

Tropical eosinophilia

Venezuelan equine encephalitis,

West Nile Fever,

Western Equine Encephalitis,

Yellow Fever,

Zika fever


Feb 2016.   The news is having a field day with the Zika virus which is not good if you are pregnant.  Otherwise causes little illness and most have no symptoms.  It is connected with microcephaly in newborns and is tragic when it happens.  The disease has spread rapidly from Africa to South and Central Americas and Mexico and Caribbean Islands.  But so has Dengue Fever and Chikungunya viruses spread to the same areas since the 1980s. There were some cases just reported in the Hawaiian Islands.   22,000 deaths occur every year from Dengue Fever and most of those are children.  A vaccine is being produced against Dengue but only 70% effective to the four strains. In Thailand and Indonesia Dengue is the leading cause of hospitalization and death in children.  I worry a lot more about Dengue than Zika.  


The Zika virus has only one strain reported to date and like the article at my web site on West Nile Disease, once immune to it as a child, then you won’t have trouble as an adult.  Eventually most children in those areas of the world will become immune so the disease when pregnant will be rare if not zero.  In the mean time there will be tragic cases.  The hope is that all these diseases will not come to America.  Probably they will not come here in great numbers because we do not have the rain fall they have and We have better control of mosquitoes.  Pregnant or potential pregnant females should not visit these countries south of the boarder since most Americans will not be immune to them. Also pregnant women should not have unprotected intercourse with men who have recently visited the disease areas. From the maps you can see it includes Mexico and the Caribbean Islands.


Dengue Virus

Approximately 1 in 4 people infected will develop disease.

Incubation: 4–7 days (range: 3–14 days)

Some patients may develop life threatening consequences and require hospitalization.

Since there are 4 distinct dengue viruses, a person can be infected up to 4 times. Infection with each dengue virus type confers lifetime immunity for that specific virus type.




Chikungunya Virus

Approximately 3 in 4 people infected will develop disease.

Incubation: 3–7 days (range: 2–12 days)

Acute symptoms typically resolve within 7-10 days.

Persons at risk for severe disease include neonates exposed intrapartum, older adults, and persons with underlying medical conditions.

Infection is thought to confer lifetime immunity.




Zika virus

About 1 in 5 people infected with Zika virus become ill (i.e., develop Zika).

The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. The incubation period (the time from exposure to symptoms) for Zika virus disease is not known, but is likely to be a few days to a week.

The illness is usually mild with symptoms lasting for several days to a week.

Zika virus usually remains in the blood of an infected person for a few days but it can be found longer in some people.

Severe disease requiring hospitalization is uncommon.

Microcephaly in infants if mother infected while pregnant.

Deaths are rare.








Zika progression in the world









Dengue Fever world progression:   Very similar to Zika.







Autosomal recessive primary microcephaly (MCPH) is a neurodevelopmental disorder that is characterised by microcephaly present at birth and non-progressive mental retardation.  MCPH is a nerve cell DNA defect when cells multiply.  Twelve MCPH DNA defects have been mapped to date from various populations around the world. Genetic counseling may help families with defective genes. Many conditions or factors can cause the break in the DNA. (Same thing in Autism which is from a damage to the DNA before birth.)

Brazil is enduring an extraordinary outbreak of microcephaly. Since last fall, more than 4,000 suspected cases have been reported, and authorities have blamed an unusual virus, Zika. But now it appears that a number of those cases may not in fact be microcephaly, or not linked to Zika.  The country is trying to find out which cases it could actually confirm by health secretariats in 26 states and one federal district spread across South America’s biggest country. After experts scrutinized many cases they found that more than half either weren’t microcephaly, or weren’t related to Zika.  Just 270 were confirmed as microcephaly that appears to be linked to Zika or other infectious diseases, according to the latest ministry bulletin.

It’s not yet clear whether the same pattern will emerge from all of the cases. And health experts say the huge number of cases is still very worrisome — as is the rapid spread of Zika through the Americas. The condition can also be caused by genetic factors, drug or alcohol abuse, during pregnancy.  It also can be caused by other infections such as CMV, Rubella, Coxsachie B, Toxoplasmosis, and even chickenpox.  Some scientists said the new data suggest that Brazil will have fewer cases of Zika-related microcephaly than originally feared. The country may have over-counted microcephaly cases because it initially asked doctors to report all births of babies with a head circumference of 33 centimeters or less — but some of those were simply children with normally small heads.

It is possible that the number of cases of microcephaly with suspected relationship to Zika will be much less.   Publicizing microcephaly on the news caused doctors to report more cases than in the years past.

Other specialists were wary of the new data, questioning the methodology that was being used since the badly affected areas, the northeastern state of Bahia, have used relatively cheaper transcranial ultrasound imaging — rather than CT brain imaging scans —  to try to confirm and discard cases of microcephaly.

In October, when the Brazilian government began requiring doctors to report suspected cases, they were instructed to notify the Health Ministry if the circumference of a newborn baby’s head was 33 centimeters or less.  In December, the ministry reduced the figure to 32 centimeters or less which is in line with WHO and USA guidelines. The ministry said many babies with the 33 cm heads were later found to be healthy. Using standard U.S. growth charts, the 33- centimeter guide would put 10 percent of American newborns in the category of suspected microcephaly — clearly way too high a percentage.

In northeastern Pernambuco state, authorities estimate that less than half of the 1,373 reported suspect cases are “possibly” related to microcephaly linked to Zika. Some children just have small heads.  



Concerning the recent outbreak of microcephaly, its cause, nor its clinical significance has yet been fully established. The Brazil health system database currently stores information on more than 100,000 neonates. A much higher than expected incidence of microcephaly was observed, varying from 2% to 8%. It normally is 1 in 6,000 babies. These findings raise questions about the condition’s diagnosis and its notification. However, the fluctuation of cases were documented since late 2012, before the entry of Zika Virus in Brazil, in mid-2014. Further questions are raised on both the surveillance of the Aedis mosquito infections, as well as the different possible causes for the outbreak.


One study classified microcephaly on three different criteria, as follows:

1. Brazilian Health Ministry criteria, where microcephaly equals an OFC smaller than 32 cm for term neonates.

2. Fenton curves, where microcephaly equals an OFC less than -3 standard deviation (SD) for age and gender.

3. Proportionality criteria, where microcephaly equals an ratio of head to height.

Neonates were classified with microcephaly according to each one of the three criteria. A separate group was created for those who fulfilled all three criteria. Finally, those who fell into the lower third in each criterion were grouped as extreme cases of microcephaly. Depending on the criteria utilized, in this sample, 4% to 8% of kids born between 2012 and 2015 had microcephaly. Neonates fulfilling all three criteria accounted for nearly 2% of the sample. If, however, only the extreme cases filling all the criteria are considered, the rate of microcephaly becomes normal.



The distribution of cases of microcephaly between 2012 and 2015 is observed in the chart. A variation through time is observed. The numbers are greater than expected since the end of 2012 and with its sharpest peak in mid-2014. If the Zika virus came to Brazil in summer of 2014, then 9 months later the cases would be elevated in 2015.  But the peak you see is in early 2014.



In 2000, Brazil reported that the prevalence of microcephaly in Brazilian newborns was 5.5 cases/ 100,000 live births and in 2010 it was 5.7 cases / 100,000 live births. Over the last three months it went up to 99 per 100.000 live births which corresponds to a twentyfold increase. In this study, independent of the classification criteria used, we demonstrated a much higher incidence of microcephaly between 2012 and 2015. Projecting our findings to the total number of live births in Paraíba area of Brazil, in 2014  the number of neonates born with microcephaly in that year would have been 4,652 by the Health Ministry proposed criteria, 2,442 by the Fenton curves and 2,907 by the proportionality criteria. Neonates classified with microcephaly by all three criteria would have been 1,105. These observations highlight the need to review the situation carefully. Many questions need to be answered prior to concluding what problem we are facing, how it came about and which consequences it is likely to bring to the Brazilian population in years to come. What is the real incidence of microcephaly in Brazil?

The numbers of very extreme cases of microcephaly, for instance, while significantly increasing over the last few months, are much smaller and until recently fell within the expected ranges for the worldwide reported incidence.



1.    Were only those extreme cases being notified?

2.    As the number of extreme cases increased over these past three or four months, did the awareness of health professionals increase and they started to notify milder forms which make up the majority of reported cases?

3.    Could a 31cm head circumference in a term newborn be within normal limits for this particular population?

4.    Could genetics or nutritional components explain these findings?

5.    Are we facing large numbers of a neurological disease or observing an anatomic variation of normality?


Points to ponder:

1.    ZIKV has been identified in Africa over 50 years ago.  Increases in microcephaly have not been reported there or in other countries with outbreaks of Zika.

2.    Is there another cause of the increase microcephaly such as malnutrition, drugs, alcohol, and other viral infections? Most of the reported cases have occurred in low-income families.

3.    Mosquito controlling strategies will help many aspects of public health other than Zika. The scare will prevent many other diseases carried by mosquitoes.

4.    This is a challenging health problem that limited information brings questions to conclusions at this early stage.


There have been outbreaks of other birth defects in the past in different countries.  Anencephaly is a condition where most of the brain is flat missing.  Estimates of the incidence of anencephaly in the United States during this century have varied from 0.3 to 7 per 1000 births.  In the United States each year there are about 1050 infants born with anencephaly.  Overall rates are highest in the Northeast and North Central regions and lowest in the Mountain and lower Plains states.   An anencephaly "epidemic" occured during the early 1930s in Boston and ProvidenceA mysterious cluster of anencephaly occurred in a three-county area of rural Washington State in 2013.  No cause was found. There were nearly two dozen cases of anencephaly in three years, a rate four times the national average.  They noted that small clusters of birth defects often turn out to be nothing more than sad coincidence. However it can be caused by diet, drugs, alcohol, and other viral infections that are hard to prove.

Texas has the Birth Defects Epidemiology and Surveillance Branch. BDES was established in 1993 as the result of an unusual cluster of anencephaly cases that occurred in Brownsville, Texas. Epidemiologic investigations revealed a higher than expected rate of neural tube defects among children born to Hispanic mothers living in South Texas. In recognition that epidemiologic resources are routinely needed to investigate birth defects clusters, the Texas State Legislature passed the Texas Birth Defects Act in 1993, which authorized the establishment of BDES.

So in conclusion, there are sometimes outbreaks of congenital defects of the brain, heart or kidneys that occur.  It is frequently just nature where there is a fluctuation in the frequency of these defects.  Some are caused by factors that we cannot discover nor prove.  The Zika virus may be causing some defects or just slightly increasing the incidence or may just be blamed for an increase that is either not real or caused by some other factor.  Time will tell.  But the news loves this scare and politicians (Obama) love to delegate 1.5 billion dollars to fix the problem. We need a vaccine for Dengue more than we need one for Zika.  Like the boy who took the “clock” to school, wait to judge this Zika thing until all the information is collected.

Roger Knapp MD