Billions face growing Zika threat in Africa, Asia and Pacific

With 1.2 billion at risk in India alone, experts have identified the as-yet unaffected parts of the world that have the right climate and abundant mosquitoes for the virus to settle, spread and propagate an epidemic like the one besetting the Americas and Caribbean.

“According to our most conservative scenario, populations living within the geographical range for the Zika virus were highest in India (1.2 billion people), China (242 million), Indonesia (197 million) Nigeria (179 million), Pakistan (168 million), and Bangladesh (163 million),” said a study quoted by AFP.

This was a theoretical possibility, however.

Travel advisories have increased substantially for visits across Asia, the Caribbean, North, Central and South America, and the Pacific Islands.

For Southeast Asia, the United States has issued a warning only for Singapore, but the UK considers Thailand high-risk and the Philippines and Indonesia as moderate risk. 

The European Centre for Disease Prevention and Control says travel to Thailand and Indonesia is risky, but omits the Philippines.

Malaysia reported its first suspected case of Zika involving a woman believed to have become infected in neighbouring Singapore, where more than 150 infections have now been confirmed. Thailand has had about 100 cases since January.

Two more cases were reported in the northern province of Chiang Mai’s San Sai district yesterday, bringing the number of infected people to nine.

The deputy chief of public health in Chiang Mai, Dr Waranyu Jamnongprasartporn, said the new cases were a Maejo University student living on the campus and an elderly person in Tambon Nong Han, who were diagnosed with the virus on Thursday. 

Both areas had been sprayed with insecticide to destroy the breeding of Zika-carrying Aedes aegypti mosquitoes at both areas, he said. 

A newly established emergency operations centre has set four target zones to spray insecticide six times and destroy larva breeding grounds. 

They include the original 140-home zone where the three first patients were found, to be monitored by 14 teams; the Moo 4 zone, covering 40 homes to be monitored by four teams; the Moo 12 zone, covering 53 homes to be monitored by five teams; and the Maejo University dormitory where students were asked to destroy mosquito breeding grounds, Waranyu said.

Sansai district chief Adul Huaknil said the area had seven Zika cases from June to August and now reported two more cases on September 1. 

He said health officials and volunteers were eradicating Aedes aegypti mosquitoes and larva and would continue for the 28 days it takes a mosquito to develop.

It is not known if immunity to the African Zika strain would offer protection against the Asian strain.

“If Zika immunity is widespread, introduced Zika will fizzle out fast,” Derek Gatherer of Lancaster University said in a comment on the study published in The Lancet Infectious Diseases.

“On the other hand, if it enters another unprotected population, we may see a repeat of what we have already seen in Brazil and other parts of Latin America.”

The research team used air travel data, maps of mosquito spread and climate conditions, and information on population density and health spending to draw up the epidemiological risk model.