Mosquito-borne viruses do occur in Vietnam, with the most commonly contracted such illness in the big cities being dengue, which is prevalent during the rainy season throughout Vietnam. Malaria is only seen along the borders with Cambodia and Laos and only very rarely in the big cities. There have been reports of people being infected with the Zika virus in municipal areas.
We advise travelers to take protection against mosquitoes very seriously. When outside, wear long sleeves and long pants after dusk. Repellents with DEET content are recommended and are available locally. Mosquito nets should be used at night wherever mosquitoes are present.