There have been reports for a couple of weeks of a dramatic increased incidence of microcephaly among newborns in Brazil. This neurodevelopment disorder is considered rare, and it can be caused by both congenital disorders, maternal illness, or environmental exposures.
The Cleveland Clinic lists these common causes on their Microcephaly page.
The growth of the skull is determined by the expansion of the brain. Microcephaly occurs most often because the brain fails to grow at a normal rate. This can be caused by a variety of conditions or exposure to harmful substances during fetal development. Some of these causes include:
- Chromosomal disorders such as Down’s syndrome, Cri du chat syndrome, Trisomy 13, and Trisomy 18
- Maternal viral infections such as rubella (German measles), toxoplasmosis, and cytomegalovirus
- Maternal alcoholism or drug abuse
- Maternal diabetes
- Mercury poisoning
- Uncontrolled maternal PKU
- Maternal malnutrition
Acquired microcephaly might occur after birth due to various brain injuries such as lack of oxygen or infection.
The theory that Brazil’s outbreak may be due to the recent importation of the mosquito-borne Zika Virus (see WHO WER: Zika Virus Outbreaks In the Americas) has been making headlines the past week - and while maternal viral infections have been linked to the disorder - this investigation is just getting underway and the cause is still unknown.
This Statement from the World Health Organization was released on Friday.
Disease Outbreak News
20 November 2015
In October 2015, the Ministry of Health (MoH) of Brazil notified PAHO/WHO of an unusual increase in the number of cases of microcephaly among newborns in the state of Pernambuco, northeastern Brazil.
As of 17 November, a total of 399 cases of microcephaly were being investigated in seven states in the northeast of Brazil. Most of the cases were registered in Pernambuco state (268). Other states that reported microcephaly cases are Sergipe (44), Rio Grande do Norte (39), Paraiba (21), Piaui (10), Ceara (9) and Bahia (8).
Public health response
In response to the situation, on 11 November, the MoH declared a national public health emergency to give greater flexibility to the investigations. National health authorities continue to investigate the cause of the event. Clinical, laboratory, and ultrasound analyses of pregnant women, mothers and newborn infants are being carried out (see the press release from the MoH dated 11 November in the related links).
Although the cause of this event is yet to be determined, information is being shared with Member States to raise awareness of the situation and to alert countries for similar events in their territories. For these reasons and to further the understanding of the etiology of this event, PAHO/WHO urges Member States to report any increase of microcephaly or other neurological disorders in newborns that cannot be explained by known causes. Recommendations by PAHO/WHO are available in the Epidemiological Alert (see related links).