Soon after Singapore reported its first case of the mosquito-borne Zika virus on Sunday, the government announced 40 more cases of the locally-transmitted infection, most of them foreign workers at a construction site. A joint statement by the Ministry of Health and the National Environment Agency stated that 34 people had fully recovered while the other seven, who were still symptomatic and potentially infectious, remain in hospital.
Thirty-six of those infected are foreign labourers working at a construction site in the area, according to the statement. The first case was that of a 47-year-old Malaysian woman residing in the city-state. The government has also clarified that at this point the community transmission appeared to be localised within the district.
"All 41 are residents or workers in a suburban district. They are not known to have travelled to Zika-affected areas recently and are thus likely to have been infected in Singapore. This confirms that local transmission of Zika virus infection has taken place."
The health ministry earlier said it expected more cases of the mosquito-borne virus which has been linked to a rare birth defect, microcephaly, in Brazil.
Singapore's National Environment Agency (NEA) said it has deployed 100 officials in the area and carried out a series of vector control operations like ultra-low volume misting of premises, thermal fogging of outdoor areas to kill adult mosquitoes, increasing frequency of drain flushing and oiling to prevent breeding, and public education outreach and distribution of insect repellent.
"NEA may need to gain entry into inaccessible premises by force after serving of requisite notices, to ensure any breeding habitats are destroyed quickly," the environment agency said in its statement.
The health ministry suspects that there is a risk of subsequent local transmission and that it expected that there would be more cases in future since "most infected persons may display mild or no symptoms".
Those infected display symptoms of mild fever, rash and red eyes while an estimated 80 percent of people infected have had no symptoms.
A small number of cases of sexual transmission have been reported in the United States and elsewhere.
A case of suspected transmission through a blood transfusion in Brazil has raised questions about other ways that Zika may spread.
The virus, which was originally confined to a narrow equatorial belt from Africa to Asia, has spread across the Pacific Ocean to more than 50 countries including the United States, Mexico and Brazil, in the last one year.
A public health emergency was declared in the US on August 12 after more than 10,000 laboratory-confirmed cases were recorded, including more than a thousand pregnant women.
Miami Beach, a popular tourist destination, is the latest to be infected and Florida health authorities have warned pregnant women not to travel there.
US health officials have concluded that Zika infections in pregnant women can cause microcephaly, a birth defect marked by small head size that can lead to severe developmental problems in babies.
The connection between Zika and microcephaly first came to light last fall in Brazil which is widely considered to be responsible for the outbreak of the virus and which has now confirmed more than 1,800 cases of microcephaly that it considers to be related to Zika infection in the mothers.
The World Health Organization has said there is strong scientific consensus that Zika can also cause Guillain-Barre, a rare neurological syndrome that causes temporary paralysis in adults.