A worker sprays insecticide outside a student dormitory to fight against dengue fever in Singapore, on July 13, 2020. (Xinhua/Then Chih Wey)

Due to the impacts of the COVID-19 pandemic and subsequent restrictions on inbound flights, Shanghai has only reported seven imported cases of dengue fever as of Jul 12, which is 77 percent lower than the same period in 2019, according to the local authorities on Thursday.

Among the seven reported cases, three are from the Philippines, while the other four are from Cambodia, Vietnam, Singapore and Sri Lanka.

As the countries that often report a high number of dengue fever cases have entered the disease outbreak season, and with the high incidence of mosquitoes during summer, the city's health authority also warned citizens should be aware of the growing risks, noting that more inbound flights and high numbers of travelers are also likely to result in more cases, according to The Paper on Thursday.

In 2019, the city reported 107 cases of dengue fever, all of which were imported; however, no deaths related to the disease were reported.

Dengue fever is common in some Asian and Latin American countries, and is a potentially fatal mosquito-borne disease, including symptoms such as fever, nausea, and muscle and joint aches.