From the 1918 Spanish flu to the Covid-19 pandemic now, here is a timeline of Singapore's fight against infectious diseases over the last 100 years.

1918: SPANISH FLU

Type of virus: H1N1

First wave: June 18 to July 27

• "Mysterious epidemic" appears in Singapore on June 18. Reported to be relatively mild, with a high illness rate but a low mortality rate. Peaks during the week ending July 6.

Second wave: Oct 3 to Nov 8

• A second intense wave occurs in October and November. Peaks during the week ending Oct 26.

• By Oct 28, the Singapore General Hospital is handicapped, with 12 out of 19 nurses ill with influenza.

• Epidemic abates by Nov 2. After Nov 8, no more cases reported.

1957: ASIAN FLU

Type of virus: H2N2

Period: April to May

• First recognised in Singapore in end-April among 30 infected inhabitants on Pulau Brani.

• By May 5, the outbreak has become an epidemic. Schools are closed for almost two weeks.

• Outbreak reaches its peak in mid-May and tapers off by the end of the month.

1968: HONG KONG FLU

Type of virus: H3N2

Period: August to September

• First detected in Hong Kong on July 13.

• On Aug 14, The Straits Times describes it as "a mild outbreak of influenza".

• The outbreak peaks between Aug 16 and 25. As it is relatively mild, no substantial public health measures are adopted.

• Virtually disappears by early September.

2002-2003: Severe acute respiratory syndrome (Sars)

Type of virus: Coronavirus

Period: March to July

• First case confirmed in Guangdong, China, in November 2002.

• On March 1, 2003, Singapore's first Sars patient, who had visited Hong Kong, is admitted to Tan Tock Seng Hospital.

• On March 12, the World Health Organisation (WHO) issues a global alert on outbreaks in Vietnam, Hong Kong and Guangdong.

• Between March and May 2003, there are 238 cases in Singapore.

• On July 16, Sars is eradicated in Singapore.

2009-2010: H1N1

Period: April 2009 to May 2010

• First detected in humans in the United States in April 2009.

• On April 30, Singapore raises its alert level to orange.

• On May 26, 2009, Singapore receives its first imported case of H1N1, a Singaporean returning from New York.

• Singapore receives its first batch of the H1N1 vaccine in end-October 2009.

• More than 415,000 people in Singapore are infected within the span of nine months.

• On Aug 10, 2010, WHO declares an end to the pandemic. The virus continues to return as a seasonal flu.

2019-present: Covid-19

Type of virus: Coronavirus

• On Jan 12, 2020, WHO confirms that a novel coronavirus caused respiratory illness in a cluster in Wuhan, China.

• On Jan 23, Singapore confirms its first imported case of Covid-19.

• On April 7, a set of stringent preventive measures dubbed the "circuit breaker" kicks in.

• As of April 18, there are 5,992 cases in Singapore.