East Africans’ immunity to Zika still unknown

Paradise blog. 

A PhD research scientist from the Ifakara Health Institute, Mr Dickson Lwetoijera, told the ‘Daily News On Saturday’ in an exclusive interview that the fact that “the virus was discovered in Africa is enough to assume that we might be immune to it from

multiple exposure’’.

Mr Lwetoijera, however, said that it is nearly seven decades from its discovery, a period, which has been accompanied by so much change, including climate change and human development, which might have led to evolution in the virus ability to infect humans (virulence).

He added that at the moment it was not known and still remains subject to research as what kind of virus variants/strains is driving the recent outbreak – as it could be different from the one that was originally discovered in 1947.

“It should be noted that this might be the same case as the avian flu virus, in which some of the strains are not virulent at all while others are so virulent,’’ Mr Lwetoijera explained.

In an article published recently in ‘Newsweek’, the virus has been linked to a massive outbreak of Brazil microcephaly -- a condition where children are born with underdeveloped brains and small heads. Between October 2015 and January 2016, more than 4,000 cases of microcephaly were recorded in Brazil, compared to just 147 cases in 2014.

The potential link between Zika and microcephaly has been declared by the World Health Organisation (WHO) as a Public Health Emergency of International Concern (PHEIC), meaning it poses a global threat that requires an international response.

But parts of the population in East Africa, including Uganda and Kenya, could already be immune to the virus, according to a medical expert and WHO official.

The virus was first identified in rhesus monkeys in Uganda’s Zika forest in 1947, before being found in humans in Uganda and Tanzania in 1952. While there is a dearth of research on Zika in Africa, outbreaks of the virus on the continent have previously been recorded, according to the WHO.

Mr Lwetoijera said that if at all we are immune to zika virus currently causing the outbreak, it will be great news as our new born babies will be safe from microcephaly and brain damage.

Scientifically, this means that the original virus strain and its current virulent variant share recognition sites (antigens), which can be recognised by our immune system (antibodies). “The only sure thing is that we are not falling ill of the disease because the transmission isn’t here yet.

The student-researcher said that all necessary precautionary measures as indicated by WHO and CDC should be taken into account. These include personal protection against mosquito bites by using repellents, nets, wearing long clothes that protect most of the body parts against bites.

Other measures include destroying all stagnant water bodies and clear vegetation around homes where mosquitoes prefer to lay eggs and hide,” he noted.

Concurring with the thoughts of Mr Lwetoijera, a PhD student of molecular epidemiology at the University of Antwerp, Mr Vito Baraka, said that the question of immunity is yet to be unravelled while researchers are currently working to find the evidence.

Mr Baraka said that the evidence might also guide vaccine development strategies against the infection. However, as of now, no systematic studies have been conducted to address the question, making it remain speculative.

He added that there can be several hypotheses that can be put forward in the current scenario like the virus in Latin America might have evolved into a more virulent form compared to the virus strains isolated in Africa (comparative genetic studies of the virus strains are needed to address the question).

“It is still unclear whether Zika related microcephaly is a silent problem in African settings. Again, we lack evidence as no studies have looked into that yet to establish the causal-effect association,” Mr Baraka pointed out. He advocated the need for better vector control, urban planning, water supply, health education and resource mobilisation to generate evidence to address these questions, particularly in our African settings.

“It is in the continent where the burden of infectious diseases is still high (malaria, HIV, TB). Potential ZIKV outbreak in our settings will undoubtedly prove too unbearable to the existing health system,’’ the researcher noted.

According to the Centre for Disease Control and Prevention website, sexual transmission of Zika virus is possible, which is of particular concern during pregnancy.

Current information about possible sexual transmission of Zika is based on reports of a number of cases. The first was probable sexual transmission of Zika virus from a man to a woman, in which sexual contact occurred a few days before the man’s symptom onset.

The second is a case of sexual transmission currently under investigation (unpublished data, 2016, Dallas County Health and Human Services).

The third is a single report of replication-competent Zika virus isolated from semen at least two weeks and possibly up to 10 weeks after illness onset; reverse transcriptase-polymerase chain reaction testing of blood plasma specimens collected at the same time as the semen specimens did not detect Zika virus.

In all three cases, the men developed symptomatic illness. Whether infected men who never develop symptoms can transmit Zika virus to their sex partners is still unknown.

Sexual transmission of Zika virus from infected women to their sex partners has not been reported. Sexual transmission of many infections, including those caused by other viruses, is normally reduced by consistent and correct use of latex condoms.