Dengue fever infections nationwide hit 40,000 in the first nine months, with 25 deaths, as the outbreak has not showed any sign of winding down.
The number of patients at the Central Tropical Diseases Hospital in Hanoi increased from 188 in August to more than 300 in September.
Nearly 80 of them are staying for treatment and every two or three of them have to share a bed.
Hanoi is among the dengue fever hot spots this year, together with Dong Nai and Binh Duong Provinces in southern Vietnam.
Ho Chi Minh City had the highest number of infections, with nearly 10,000 cases during the first nine months, up 66 percent from the same period last year and including four deaths.
Doctors said the mosquito-borne disease has a cyclical pattern and tends to become very severe after three to five years.
They said many fatalities this year were due to late admission, when the virus has caused kidney, liver, lung, or heart failure. Adults can suffer brain hemorrhage in severe cases.
The disease has typical flu-like symptoms such as persistent high fever, muscular and joint pain, nausea, belly and headache, rashes or blood spots under the skin.
Doctors said local authorities should strictly impose cash fines on those who do not cooperate with health authorities to stop the virus from spreading, for instance by storing water outdoor and creating a favorable environment for mosquito reproduction.
Cash penalties are rarely imposed.
Authorities in Ho Chi Minh’s Binh Thanh District, one of the areas prone to the disease, have fined several families VND750,000-1.5 million each since late August.