An outbreak of yellow fever in Angola in which hundreds have already died could be "a threat to the entire world", the World Health Organisation has warned.
Cases of the mosquito-borne virus were first reported in Angola's capital Luanda in December. The disease has now spread to 16 of the country's 18 provinces.
So far, thousands of people are suspected to have been infected with the disease and 238 people have died, WHO has reported.
"The evolution of the situation in Angola is concerning and needs to be closely monitored," it stated in a report.
People travelling from Angola have already exported the virus to China, Kenya and the Democratic Republic of Congo, where at least 21 people are reported to have died.
The trend has sparked concerns among the WHO, which fears the virus is at risk of spreading further because of the large international communities living in Angola that regularly travels to neighbouring countries.
Countries where there are Aedes mosquitos, carriers of the yellow fever virus, are particularly at risk. Areas where there have been previous outbreaks of Dengue, Chikungunya or Zika virus would also be fertile grounds for the disease to spread.
WHO has called for "an urgent need to strengthen the quality of the response in Angola" and increase the control of travellers' immunisation status, when coming from areas affected by the virus.
Together with UNICEF, the Centers for Disease Control and Prevention and Médecins Sans Frontières (MSF), WHO is monitoring the situation in Angola and a situation of emergency has been declared.
Battling the zika virus - in pictures
Battling the zika virus - in pictures
A worker of the Salvadorean Ministry of Health fumigates a house in Soyapango, 6 kilometers from San Salvador, El Salvador. Salvadorean authorities have began a three days campaign of fumigation to reduce the presence of the mosquito that transmit the Zika virus.
A Health Ministry employee fumigates a home against the Aedes aegypti mosquito to prevent the spread of the Zika virus in Soyapango, six km east of San Salvador. Health authorities have issued a national alert against the Aedes Aegypti mosquito, because of the link between the Zika virus and microcephaly and Guillain-BarrÈ Syndrome in foetuses.
AFP PHOTO/Marvin RECINOSMarvin RECINOS/AFP/Getty Images
A pediatric infectologist examines a two-months-old baby, who has microcephaly, on 26 January 2016 in Recife, Brazil.
A woman walks through the fumes as Health Ministry employee fumigate against the Aedes aegypti mosquito to prevent the spread of the Zika virus in Soyapango.
Marvin RECINOS/AFP/Getty Images
A health ministry employee sprays to eliminate breeding sites of the Aedes Aegypti mosquito, which transmits diseases such as the dengue, chicunguna and Zica viruses, in a Tegucigalpa cemetery on January 21, 2016. The medical school at the National Autonomous University of Honduras (UNAH) recommended that women in the country avoid getting pregnant for the time being due to the presence of the Zika virus. If a pregnant woman is infected by the virus, the baby could be born with microcephaly.
AFP PHOTO/Orlando SIERRA
A man walks away from his home with his son as health workers fumigates the Altos del Cerro neighbourhood as part of preventive measures against the Zika virus and other mosquito-borne diseases in Soyapango, El Salvador
A three-months-old, who has microcephaly, in Recife, Brazil.
A pregnant woman waits to be attended at the Maternal and Children's Hospital in Tegucigalpa. The medical school at the National Autonomous University of Honduras (UNAH) recommended that women in the country avoid getting pregnant for the time being due to the presence of the Zika virus. If a pregnant woman is infected by the virus, the baby could be born with microcephaly.
ORLANDO SIERRA/AFP/Getty Images
Army soldiers apply insect repellent as they prepare for a clean up operation against the Aedes aegypti mosquito, which is a vector for transmitting the Zika virus in Sao Paulo, Brazil.
AP Photo/Andre Penner
Workers disinfect the Sambadrome in Rio de Janeiro to fight the spread of the Zika virus
Dr. Vanessa Van Der Linden, the neuro-pediatrician who first recognized the microcephaly crisis in Brazil, measures the head of a 2-month-old baby with microcephaly in Recife
Mother Mylene Helena Ferreira cares for her son David Henrique Ferreira, 5 months, who has microcephaly, on January 25, 2016 in Recife, Brazil. In the last four months, authorities have recorded close to 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants
U.S. women who are pregnant from traveling to many South American countries
In the last four months, authorities have recorded close to 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants.
Dr. Vanessa Van Der Linden, the neuro-pediatrician who first recognized the microcephaly crisis in Brazil, examines a two-month-old baby with microcephaly on January 27, 2016 in Recife, Brazil
Brazil is one of the countries in South America where the Zika virus has taken hold
Health workers fumigating to combat Zika virus in Lima, Peru. The US have already issued a warning urging pregnant women to avoid travel to Latin American countries
Two-month-old Jose Wesley, born with microcephaly in Brazil, is nursed by his brother
No travel or trade restrictions to Angola have yet been advised.