A northeastern Japan city recently urged caution to the media on the use of the shortened popularized moniker "Mambo" -- a play on words for stronger measures against the novel coronavirus and its ocean sunfish symbolic of its post-disaster reconstruction.

A document distributed by Kesennuma, Miyagi Prefecture, comes amid calls that the use of the nickname could diminish the seriousness of the central government's move to designate Osaka, Hyogo and Miyagi prefectures for stronger measures against increasing COVID-19 cases.

People wearing face masks walk on a shopping street in Sendai in Miyagi Prefecture, northeastern Japan, on April 1, 2021. The Japanese government is set to allow Osaka, Hyogo and Miyagi prefectures to take stricter anti-coronavirus measures under a revised law that took effect in February as they have been hit by a resurgence in new infections. (Kyodo) ==Kyodo

The steps, including fines for eateries that ignore mandates to shorten operating hours, will be effective from April 5 for one month. The designation was made as the three prefectures experience a rise in virus numbers, with Osaka logging a record 666 infections Saturday.

The word affiliation could "negatively affect the image of the popular ocean sunfish, as well as a recovering roadside facility (in Kesennuma)" which uses the sunfish as its logo, according to the document. The sunfish lives in the area's waters.

Kesennuma is one of the areas hit hardest by the 2011 earthquake and tsunami that struck northeastern Japan.

The phrase had been used as an unofficial nickname by experts from around February. It was further popularized after Shigeru Omi, head of the government's COVID-19 subcommittee, repeatedly used it in a press conference with Prime Minister Yoshihide Suga on March 18, when the government made the decision to lift the state of emergency in the Tokyo region.

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The "mambo" moniker -- which makes people associate stronger pandemic measures with the large, slow moving fish -- caused a stir on social media, with one Twitter user criticizing the "lack of a sense of crisis" in using such nickname, saying, "Why abbreviate?"

It also garnered criticism from Yasutoshi Nishimura, minister in charge of Japan's coronavirus response, who called it "silly" and "lacking in gravity."

In a press conference on Friday, Omi admitted that the nickname was "inappropriate" and said he would refrain from using it.

Tsutomu Hatakeyama, director of Kesennuma's tourist division, said, "It may be oversensitive, but we want to avoid associating the sunfish with the coronavirus."

Masamichi Onodera, who manages the city's roadside facility with a sunfish logo, said while the nickname may be taken as having an optimistic spin on the recent anti-virus measures, he "also understands how the city felt."