Monitoring the incidence of microcephaly iin infants born to women infected with Zika Virus in Colombia.

Zika Virus is a form of Mosquito-born Flavivirus (the group of RNA Viruses that also includes the Yellow Fever and Hepatitis C Viruses), which first emerged in Central Africa in 1947. Infection with Zika is generally associated with a rash and a fever, but symptoms are variable and include nonpurulent conjunctivitis, headache, pruritus, arthralgia, myalgia, or malaise. In 2007 an epidemic in Micronesia was associated with a new and worrying symptom, microcephaly, a severe congenital defect affecting infants born to women infected with the Virus, in which the brain fails to develop fully during pregnant, and the child is born with a much reduced cranium, leading to life-long disabilities. This symptom appeared again in a second outbreak that began in Brazil in April 2015 and which has since spread across much of the Americas.

In a paper published in the Centers for Disease Control and Prevention Prevention Morbidity and Mortality Weekly Report on 9 December 2016, a team of scientists led by Esther Liliana Cuevas of the Instituto Nacional de Salud in Bogotá present the results of a study which monitored the rise in the incidence of microcephaly associated with the spread of Zika Virus in Colombia in 2016.

Microcephaly, and other major birth defects, are routinely recorded in Colombia, so the country was already equipped with a system for monitoring the condition at the outset of the the epidemic. The first case of Zika was recorded in Colombia in August 2016; however the methodology by which the disease was diagnosed was variable and changed over the course of the epidemic, leading to some inconsistencies in the way data was recorded, so that not all cases of microcephaly were screened for Viral RNA. 

Cuevas et al. examined data from 31 January to 12 November 2016, during which period 476 instances of microcephaly were recorded in Colombia, compared to 110 over the same period in 2015. This equates to 9.6 cases per 10 000 live births in 2016, compared to 2.1 cases per 10 000 live births in 2015. This is also higher than the 5.5 cases of microcephaly per 10 000 live births recorded in Brazil in 2015, where the Zika epidemic was already present, though in Brazil microcephaly was not routinely recorded before the epidemic, so it is likely that cases were missed.

Microcephaly was reported in 28 of Colombia's 33 reporting areas (33 departments plus the federal capitol area) for medical records, with the instances of the condition ranging from two cases per 10 000 live births in Nariño and Quindío departments to 29 cases per 10 000 live births in Amazonas Department. Interestingly, much of Colombia is more than 2000 m above sea level, at which altitude the Mosquitoes that spread the disease cannot survive, but these high altitude areas also suffered a rise in reported cases of microcephaly. If these cases were due to Zika Virus then they presumably either travel related infections (i.e. the mother had travelled to an area where the Virus could be transmitted by Mosquitoes) or instances of sexual transmission (like many Viruses, Zika can be transmitted by sexual intercourse with an infected person, though this is not the main means of transmition).

Prevalence of congenital microcephaly per 10,000 live births during epidemiologic weeks 5–45 (January 31–November 12), by reporting area — Colombia, 2016. Cuevas et al. (2016).

Due to the irregularities in the way Zika infection was recorded, it was not possible to accurately assess what proportion of these cases were infected with Zika, nor what proportion of pregnant women infected with Zika produced babies with microcephaly. However procedures were in place for screening cases for other diseases which are known to cause microcephaly; Syphilis, Toxoplasmosis, Rubella (German Measles), Cytomegalovirus, and Herpes Simplex Virus. Of the 476 cases of microcephaly, 121 were screened for these agents, 26 of which proved to have such an infection. Of these 15 were infected with Toxaplasmosis (14 of which were also confirmed to be infected with Zika), six were infected with Herpes Simplex Virus (two of which were also confirmed to be infected with Zika), four were infected with Cytomegalovirus (one of which was also confirmed to be infected with Zika) and one had Syphilis.

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First case of locally transmitted Zika Virus reported in Texas.

Zika Virus is a form of Mosquito-born Flavivirus (the group of RNA Viruses that also includes the Yellow Fever and Hepatitis C Viruses), which has been reported episodically in warm regions of Africa and Asia since the 1940s and in the Americas since 2015. In most cases it causes only a mild fever, however in cases where pregnant women have been infected it has been linked to cerebral birth defects, including microcephaly, a severe underdevelopment of the brain of an infant, leading to life-long disabilities.

The disease was first reported in the Americas in April 2015, and since then has spread to a number of other South and Central American and Caribbean nations, with cases reported in other countries across the globe linked to infection in the Americas. The first case of Mosquito transmission of the disease withing the United States was reported in Miami-Dade County in Florida in August this year.

In a press release issued on 28 November 2016 the Texas Department of State Health Services reported the first known case of Mosquito transmission of Zika Virus in the state. The infection was reported in a (non-pregnant) woman in Cameron County who had not travelled to any area of known transmission.

Zika Virus envelope model, coloured by chains. Sirohi et al. (2016)/Wikipedia.

To date Texas has reported 257 cases of Zika infection, with almost all of these attributed to infection overseas in patients that had travelled to areas of known infection. Four other cases where this was not the case have been reported, two of which were infants born to infected mothers and two of which have been attributed to sexual transmission (like many Viruses, Zika can be passed through sexual contact, though this is not the main form of infection).

Representatives of the Texas Department of State Health Services, Cameron County Department of Health and Human Services and Centers for Disease Control and Prevention are currently carrying out door-to-door visits in Cameron County and the City of Brownsville, giving advice on recognising Zika symptoms and eliminating Mosquito breeding-habits close to homes, as well as collecting urine samples for screening for the virus.

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Determining the origin of the August 2016 Singapore Zika Virus outbreak.

Zika Virus was first recoded in 1947 in Rhesus Monkeys in Uganda, with a series of sporadic Human infections recorded in Africa and Equatorial Asia in the later part of the twentieth century. In 2007 a larger outbreak was recorded on the island of Yap in Micronesia, which was followed by a second outbreak in French Polynesia in 2014-15. This Polynesian outbreak was particularly worying as it was linked to a variety of congenital cerebral defects, including microcephaly (extreme underdevelopment of the brain in infants, leading to severe learning disabilities). This was followed by a larger outbreak in 2016 which originated in Brazil and spread to a number of other American nations, an outbreak which was again linked to a cerebral defects, including microcephaly.

In August 2016 a cluster of Zika cases was detected in Singapore, causing fears that the disease may have spread from Brazil, and might present a danger to pregnant women in the country. In a paper published in the journal Eurosurveillance on 22 September 2016, a team of scientists led by Sebastian Maurer-Stroh of the Bioinformatics Institute of the Agency for Science, Technology and Research in Singapore, the Department of Biological Sciences at National University of Singapore, the School of Biological Sciences at the Nanyang Technological University and the National Public Health Laboratory of the Singapore Ministry of Health, describe the results of a series of an investigation into the Singapore Zika Virus outbreak.

The Zika Virus. Getty Images.

The Zika Virus has been known to be split into two distinct lineages, the African and Asian lineages, with the Micronesian, Polynesian and Brazillian epidemics all being derived from the Asian strain. Importantly the Polynesian and Brazilian Zika Viruses are more closely related to one-another than to any other recorded strain of the Virus, implying that the cerebral defects that are associated with the Virus are probably the result of a mutation present only in these strains.

Maurer-Stroh et al. tested 153 patients showing Zika-like symptoms (rash, polyarthralgia and low grade fever, and in a number of cases had mild conjunctivitis) in Singapore on 27-28 August 2016. Of these 53 tested positive for the Virus. RNA sequencing of the Viruses (Zika is an RNA Virus which lacks DNA) revealed that the Singapore Virus belonged to the Asian strain, and though it was outside the Polynesia/Brazil cluster, it was more closely related to this cluster than any other tested strain.

Maximum likelihood phylogenetic tree of representatives from the African lineage coloured red and Asian lineage coloured blue or cyan. The tight cluster with strains from French Polynesia and the Americas is in blue and strains from south-east Asia are in cyan. Maurer-Stroh et al. (2016).

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Florida State Department of Health Confirms local transmission of Zika Virus in Miami Dad County.

The Florida State Department of Health has confirmed that there is a high likelihood that at least four cases of Zika Virus in Miami-Dade County are the result of local transmission; i.e. that the patients have caught the Virus locally, rather than while travelling in another area where the Virus is endemic. Zika Virus is a Mosquito-transmitted disease that usually only causes a rash, mild fever and/or joint pain. However a recent epidemic of the disease, centred on Brazil and affecting a number of other South and Central American countries and Caribbean Islands, has been linked to a range of birth defects, in particular microcephaly, severe underdevelopment of the brain leading to profound life-long learning disabilities.

A total of 331 case of Zika have been reported in Florida, including 55 affecting pregnant women, with the largest clusters of infections in Miami-Dade (99 cases), Broward (55 cases) and Orange (40 cases) counties. The Florida State Department of Health is carrying out active monitoring of affected areas, including door-to-door outreach and urine sample collection, as well as trapping and testing of Mosquitoes. While no Zika-positive Mosquitoes have yet been discovered, the Department is confident that the state has at least one area where local transmission of Zika Virus is occurring, an area in Miami-Dade County bounded by NW 5th Avenue to the west, US 1 to the east, NW/NE 38th Street to the north and NW/NE 20th Street to the south.

The confirmed area of the Miami-Dade Zika Virus outbreak. Google Maps/Florida State Department of Health.

As a precautionary measure local blood banks are excluding donors from areas where Zika has been reported, and the Florida State Department of Health is recommending any women who have travelled to affected areas should seek testing for the Virus and additional ultrasound scans from their healthcare provider. It also recommends that all Floridians protect themselves against Zika and other Mosquito-transmitted diseases by regularly draining any standing water close to their homes, by covering windows with screens and using Mosquito repellent when outdoors.

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