It extends nationwide a policy already in place in the capital, Mexico City, where most restaurants, cinemas and bars have been closed since last weekend.
City authorities say initial evidence suggests infection rates there are slowing.
Some factories will stop production and schools are already closed. Residents have been urged to stay at home.
But some people say they will ignore it because they cannot afford not to work.
There is also growing concern at the effect the virus could have on Mexico's already-struggling economy.
The number of confirmed cases of swine flu infection in Mexico now stands at more than 300, officials say.
Mexican Health Secretary Jose Angel Cordova said on Friday that three more deaths from swine flu had been confirmed, bringing the toll to 15.
The virus is suspected of causing more than 160 other deaths.
Announcing the figures, Mr Cordova said that new cases of the virus were levelling off.
"The fact that we have a stabilisation in the daily numbers, even a drop, makes us optimistic," he said.
But Dr Keiji Fukuda, acting assistant director general of the World Health Organization, said fluctuations were to be expected. "If it didn't do that [it] would be very unusual," he said.
In other developments:
• The US has announced that it will buy 13 million new courses of antiviral treatment and send 400,000 of them to Mexico
• An aide to US Energy Secretary Stephen Chu who helped arrange President Obama's recent trip to Mexico is being tested for swine flu, AP reports, although the aide is said not to have been in contact with the president
• The head of the US Centers for Disease Control and Prevention says it is fine for people without flu symptoms to fly and use the subway, a day after Vice-President Joe Biden said he would advise his own family members against using public transport
• Denmark reports its first confirmed case of swine flu
• German authorities confirm that a nurse who treated a patient with swine flu also contracted the disease, in the first person-to-person transmission in the country
• Test results confirm the UK's first person-to-person transmission of swine flu, in a friend of a couple from Scotland who were first in the country to be diagnosed with the virus
• Mexico says it will lodge a formal challenge at the World Trade Organisation demanding explanations from countries that have banned imports of Mexican pork products
On Thursday European health ministers held an emergency meeting on measures to tackle the virus, which has now been confirmed in seven European countries.
SYMPTOMS - WHAT TO DO
Swine flu symptoms are similar to those produced by ordinary seasonal flu - fever, cough, sore throat, body aches, chills and fatigue
If you have flu symptoms and recently visited affected areas of Mexico, you should seek medical advice
If you suspect you are infected, you should stay at home and take advice by telephone initially, in order to minimise the risk of infection
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.