Until the middle of the last decade the mosquito vectored Zika Virus (ZIKAV) was relatively unknown outside of Africa, but that began to change in 2007 when it was carried by a traveler to Yap Island in the South Pacific (see 2009 EID Journal Zika Virus Outside Africa by Edward B. Hayes) and rapidly spread to roughly 70% of the island’s inhabitants.
Zika gained notoriety again in 2011 when the EID Journal carried a a remarkable Dispatch on the first Probable Non–Vector-borne Transmission of Zika Virus, Colorado, USA, involving two researchers infected in Africa, one of whom returned to the Untied States and passed the virus (presumably via sexual contact) on to his wife.
This was the first instance where sexual transmission of an Arbovirus was suspected, the author’s writing:
Results also support ZIKV transmission from patient 1 to patient 3. Patient 3 had never traveled to Africa or Asia and had not left the United States since 2007. ZIKV has never been reported in the Western Hemisphere. Circumstantial evidence suggests direct person-to-person, possibly sexual, transmission of the virus.
Generally described as producing a `mild and self-limiting’ illness, two years ago the Zika story took another turn when it arrived in French Polynesia, infecting thousands, and for the very first time we started seeing evidence of more severe neurological illness (see Zika, Dengue & Unusual Rates Of Guillain Barre Syndrome In French Polynesia).
As Chikungunya had done in the fall of 2013, the Zika Virus arrived in the Americas in the spring of 2014 (Easter Island), and local transmission was reported by Brazil in May of 2015 in the north-eastern part of the country. In the six months since then the virus has spread across much of Brazil, and this fall has been reported in Columbia and Suriname (see WHO WER: Zika Virus Outbreaks In the Americas).
As this virus spreads rapidly across more heavily populated regions of the world we are starting to get a better idea of its impact on human health, and it’s previous `mild & self-limiting’ description is deserving of a second look.
This week the Brazilian government announced that concurrent with the arrival of the Zika Virus, they’ve seen a 10-fold increase of microcephaly birth defects in several states (see Microcephaly In Brazil - Background & WHO Statement), reporting 399 cases as of November 17th.
Microcephaly is a neurological condition where the child’s head is smaller in circumference than normal, and is often associated with developmental disorders. It can be caused by congenital disorders, maternal illness, or environmental exposures.
In the past week, that number has jumped to 739 across 9 states, with the following statement from Brazil’s Ministry of Health released on Tuesday:
Registration Date: 11/24/2015 14:11:14 changed the 11/24/2015 in the 14:11:45
Until November 21, 2015, it was reported 739 suspected cases of microcephaly, identified in 160 municipalities in nine states of Brazil, according to the second edition of epidemiological report on microcephaly, released on Tuesday (24). The government remains making every effort to monitor and investigate, as a priority, the increasing number of cases of microcephaly in the country.
The Pernambuco state keeps with the highest number of cases (487), being the first to identify an increase of microcephaly in your area and which has the follow-Ministry of Health team since October 22. Next are the states of Paraíba (96), Sergipe (54), Rio Grande do Norte (47), Piauí (27), Alagoas (10), Ceará (9), Bahia (8) and Goiás (01). Among the total number of cases was reported a suspicious death in the state of Rio Grande do Norte. This case is under investigation to determine the cause of death.
All of which brings us to the Rapid Risk Assessment published yesterday (but using the week-old number of 399 cases) by the ECDC which looks at the suspected – but not confirmed – link between the Zika virus and this surge in microcephaly.
You’ll almost certainly want to download the full PDF, which provides an excellent overview of the the virus, and the current situation.
25 Nov 2015
New ECDC risk assessment evaluates the possible link between the observed increase of congenital microcephaly in Brazil and Zika virus (ZIKV) infection and assesses the potential risks associated with ZIKV infection for travellers, the EU, and the EU Overseas Countries and Territories and Outermost Regions.
There is currently only ecological evidence of an association between the two events, while a possible causative association cannot be ruled out; further investigations and studies are needed to understand the association and the possible role of other factors, states the ECDC risk assessment.
In November the Brazilian Ministry of Health declared a public health emergency in relation to an unusual increase in the number of children born with microcephaly in 2015.
The north-Brazilian state of Pernambuco has reported 141 cases of microcephaly in newborns in 2015, in comparison to an average of 10 cases per year from 2010–2014. A ten-fold increase in the incidence of microcephaly among newborns was observed in other north-eastern Brazilian states.
As the increase is within nine months of the Zika emergence, the Ministry of Health of Brazil has suggested a possible relationship between the increase in microcephaly and the ongoing Zika outbreak. While investigations are still ongoing, the authorities issued specific recommendations for pregnant women relating to protection from mosquito bites: such as keeping doors and windows closed or screened, wearing trousers and long-sleeved shirts and using repellents.
In comparison, in French Polynesia there was an increase of central nervous system malformations in foetuses and newborns following an epidemic of ZIKV infection: at least 17 such cases were reported during 2014–2015, coinciding with the Zika outbreaks on the French Polynesian islands, four tested women were found positive for flavivirus.
Congenital microcephaly is a descriptive diagnosis for a neurodevelopmental disorder causing small head of the newborn. It can be caused by a variety of factors, such as genetic disorder, brain injury, consumption of teratogenic drugs, exposure to chemicals as well as transplacental infections.
The involvement of ZIKV in microcephaly is not documented in the scientific literature, however, other Flavivirus infections are known to have the potential to cause premature birth, congenital defects and microcephaly.
ECDC risk assessment states that:
- Travellers to countries where ZIKV is circulating are at risk of getting the disease through mosquito bites.
- During the winter season the risk for transmission of Zika is extremely low in the EU as the climatic conditions are not suitable for the activity of mosquito vector species.
- As the Zika epidemic is currently spreading in South America, the introduction of the virus from Brazil, Colombia, and Suriname or from Cape Verde to EU Overseas Countries and Territories and EU Outermost Regions, especially in the vicinity is possible.
ECDC risk assessment lists risk mitigation options for public health authorities in the EU/EEA, including precautions that are advisable to travellers to affected areas, particularly pregnant women.
Zika virus disease is a mosquito-borne viral disease which can be transmitted by invasive mosquito species, such as Aedes aegypti and Aedes albopictus. The disease symptoms, i.e. fever, joint swelling, rash, headaches, are usually mild and last for 2 to 7 days.
Read the risk assessment: Microcephaly in Brazil potentially linked to the Zika virus epidemic
Like Chikungunya, and Dengue before it, Zika appears to be well poised to establish itself across a wide range of the Caribbean, Central and South America. All of which makes getting to the bottom of this epidemiological mystery a high priority.