On 31 December 2015, the National IHR Focal Point (NFP) of the United States of America notified PAHO/WHO of the first laboratory-confirmed case of Zika virus infection in the Commonwealth of Puerto Rico, an unincorporated territory of the United States. The patient is a resident of Puerto Rico and had no travel history outside the island in the three months prior to the onset of illness. A blood sample obtained from the patient tested positive for Zika viral RNA by reverse transcription polymerase chain reaction (RT-PCR).
Public health response
Epidemiological investigations are ongoing to determine the source of exposure and detect possible additional cases. Vector control efforts by the Department of Environmental Health, including inspections to identify mosquito breeding sites, is underway. The public is being urged to take preventive measures to avoid mosquito bites.
The proximity of mosquito vector breeding sites to human habitation is a significant risk factor for Zika virus infection. Prevention and control relies on reducing the breeding of mosquitoes through source reduction (removal and modification of breeding sites) and reducing contact between mosquitoes and people. This can be achieved by reducing the number of natural and artificial water-filled habitats that support mosquito larvae, reducing the adult mosquito populations around at-risk communities and by using barriers such as insect screens, closed doors and windows, long clothing and repellents. Since the Aedes mosquitoes (the primary vector for transmission) are day-biting mosquitoes, it is recommended that those who sleep during the daytime, particularly young children, the sick or elderly, should rest under mosquito nets (bed nets), treated with or without insecticide to provide protection.
During outbreaks, space spraying of insecticides may be carried out following the technical orientation provided by WHO to kill flying mosquitoes. Suitable insecticides (recommended by the WHO Pesticide Evaluation Scheme) may also be used as larvicides to treat relatively large water containers, when this is technically indicated.
Basic precautions for protection from mosquito bites should be taken by people traveling to high risk areas, especially pregnant women. These include use of repellents, wearing light colored, long sleeved shirts and pants and ensuring rooms are fitted with screens to prevent mosquitoes from entering.
WHO does not recommend any travel or trade restriction to the United States of America based on the current information available.