A dengue fever outbreak in Da Nang is the worst in 10 years, with 21 times more patients recorded this year than over the same period in 2009.
As of Monday, 713 dengue patients had been recorded this year year, equal to the total number in the first ten months last year.
City health authorities have recognized 183 dengue hot spots, and have said the outbreak is very unusual.
Officials from Da Nang Preventive Health Center said weather had been unpredictable lately with sudden bursts of both sun and rain.
They also blamed the outbreak on many construction projects around the city that have created conditions conducive to the spreading of the virus by leaving large cleared land lots dirty and damp.