As of Wednesday, the government reported there had been more than 7000 cases, mostly in the southern manufacturing hub of Foshan.

Here’s what to know about chikungunya:

Chikungunya is a disease caused by a virus of the same name.

The chikungunya virus was first identified in people sickened during an outbreak in Tanzania in 1952. Its name is derived from a word in the Makonde language, which means “that which bends up,” due to the severe pain it can cause.

Chikungunya is transmitted by infected mosquitoes and mostly causes mild symptoms. The majority of people who get chikungunya recover without needing medical attention after one to two weeks.

What are the symptoms of chikungunya?

Chikungunya typically produces symptoms including fever, muscle pain, nausea, fatigue and a rash.

But in rare cases, it can cause debilitating joint pain that persists for months or even years. Patients who get severely ill often require hospitalisation because of the risk of organ damage.

The World Health Organisation says severe cases and deaths are rare and mostly occur in babies or elderly people with underlying health conditions.

Is there a treatment or vaccine?

There is no specific treatment for chikungunya, but health workers can treat the symptoms by giving medicines to lower fevers or ease muscle pain.

Two vaccines have been approved in several regions, including Britain, Brazil, Canada and Europe.

Those are mostly targeted at travellers and are not widely available in the countries most affected by chikungunya.

Where does chikungunya normally occur?

Chikungunya causes regular outbreaks in Africa, Asia and the Americas, with occasional small epidemics in Europe.

As of July, there have been about 240,000 cases of chikungunya, including 90 deaths in 16 countries, according to the European Centres for Disease Prevention and Control.

The countries that reported the highest number of infections were Brazil, Bolivia, Argentina and Peru.

What’s happening in China?

An outbreak of chikungunya in Foshan, near Hong Kong, has prompted Chinese authorities to take measures like distributing mosquito nets, having workers spray residential areas, streets and construction sites with insecticide.

People who do not empty bottles, flower pots or other outdoor receptacles, where water might accumulate and allow mosquitoes to breed, can be subject to fines of up to 10,000 yuan ($2140) and have their electricity cut off.

The US has issued a travel advisory telling citizens not to visit China’s Guangdong province, the location of Donguan and several other business hubs, along with countries such as Bolivia and island nations in the Indian Ocean.

Unusually heavy rains and high temperatures this year have worsened the crisis in China.

Are we seeing more chikungunya outbreaks?

The number of outbreaks has increased since 2000, just as there have been more outbreaks of other mosquito-transmitted diseases like dengue and Zika, according to Robert Jones, an assistant professor at the London School of Hygiene and Tropical Medicine.

Jones said in a statement that in 2013, chikungunya was first seen in the island of St. Martin and that over the next three years, cases were confirmed in almost 50 countries in the Caribbean and the Americas, with more than 1 million suspected cases.

Jones said the risks of chikungunya epidemics have risen due to climate change and urban expansion, warning that the disease could spread to other parts of southern China with humid climates and dense cities.