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[CAPE TOWN] The Asian-linked form of Zika, responsible for abnormal smallness of the head in newborns, has been identified in Angola.
 
Zika virus is spread by daytime-active Aedes mosquitoes, causing a medical condition called microcephaly during which a baby’s brain development becomes incomplete, resulting in abnormal smallness of the head.

According to the Centre for Disease Control and Prevention, Zika can be passed from a pregnant woman to her foetus and infection during pregnancy can cause certain birth defects. Zika has no vaccine or medicine.

The study published last week (1 October) in The Lancet Infectious Diseases says that Zika virus infections and cases of suspected microcephaly have been detected in Angola since late 2016 but the origins and diversity of the virus remained unknown, thus motivating researchers to assess the emergence and circulation of Zika virus in the country.

“This represents the first known outbreak of Asian-linked Zika virus in Africa.”

Joana Morais, Ministry of Health, Angola

Researchers analysed serum samples collected by the Angolan Ministry of Health between December 2016 and October 2018 from 54 people suspected to be having Zika virus infection, and identified four positive cases of Zika. This analysis, combined with genome sequencing and mobility data, revealed the Asian-linked virus was likely introduced to Angola from fellow lusophone Brazil, and circulated in Angola for about 17 months.

“This represents the first known [occurrence] of Asian-linked Zika virus in Africa,” says Joana Morais, study co-author and director of the public health laboratory at the Ministry of Health in Angola. “Our data shows it’s spreading worldwide and bringing public health burdens that are very high, especially to African countries” she says. 

According to the World Health Organization, 800,000 suspected and confirmed cases of Asian-linked Zika have been recorded in the Pacific and the Americas. In Africa, however, information on the incidence and prevalence of Zika is limited.

The study involved an international team from the Angolan Ministry of Health, UK-based University of Oxford and the Ministry of Health in Portugal.

According to Morais, there are two types of Zika virus: the Asian lineage identified in this study, and the African lineage. Up until now, only the African type has been identified on the continent.
 
“While the African lineage is very common on the continent, it isn’t connected to the high number of cases of microcephaly associated with the Asian lineage,” she says.
 
She tells SciDev.Net that many of the children born with the condition are abandoned, adding further stress to the public health problem.
 
Jacqueline Weyer, a senior medical scientist from the National Institute for Communicable Diseases in South Africa, says the picture of Zika on the continent may still not currently be understood. This poses challenges to implementing prevention measures.
 
“We can only design effective interventions to control or prevent a disease if we have a thorough understanding of how, when and where it occurs,” Weyer explains. “But in many respects, surveillance for infectious diseases are not sufficient in most African countries for meaningful public health interventions to follow.”
 
Using handheld DNA sequencing devices, researchers were able to track the origin of the Zika outbreak in Angola.

“This technology allowed us to sequence the whole genome of the virus on-site, with very little expense,” says Morais.
 
She explains that this is the first time such technology was used in Angola and it can improve surveillance for other mosquito-borne diseases such as yellow fever, dengue and malaria.
 
“With this technology, resource-limited countries in Africa and South America can take action to reduce mortality and the tremendous public health impact of these diseases,” she says. But Jo Barnes, a senior lecturer at the Department of Global Health at Stellenbosch University in South Africa, tells SciDev.Net that the adoption of such technology may take time.
 
“There are many competing health problems in these areas that also demand action and the resources to address them are meagre,” she says.
 
“Financial constraints will preclude the widespread availability of this technology and the trained staff to operate it,” Barnes adds.
  
This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.


References

Sarah C. Hill and others Emergence of the Asian lineage of Zika virus in Angola: an outbreak investigation (The Lancet Infectious Diseases, 1 October 2019)